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19-2859; Rev 0; 4/03
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
General Description
The MAX9720 stereo headphone amplifier combines Maxim's patented DirectDrive architecture and SmartSenseTM, an automatic mono/stereo detection feature. Conventional headphone amplifiers require a bulky DC-blocking capacitor between the headphone and the amplifier. DirectDrive produces a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, saving cost, board space, and component height. SmartSense automatically detects the presence of a short at either the left or right amplifier output. Under a fault condition, the shorted output is automatically disabled and the stereo input signal is automatically mixed and routed to the remaining active channel. This feature is useful in cell phone and PDA applications where a variety of headphone jacks with unknown loads can be inserted into the headphone jack socket. SmartSense prevents both damage to the amplifier and eliminates battery drain into a shorted load. The MAX9720 delivers up to 50mW per channel into a 16 load and has an ultra-low 0.003% THD+N. A high (92dB at 217kHz) power-supply rejection ratio (PSRR) allows the device to operate from noisy digital supplies without additional power conditioning. The gain of the MAX9720 is set internally, further reducing component count. Two gain options are available (-1V/V, MAX9720A and -1.41V/V, MAX9720B). The headphone outputs include a comprehensive click-and-pop circuitry that eliminates audible glitches on startup and shutdown. A shutdown mode provides a fast 250s turn-on time. The MAX9720 operates from a single 1.8V to 3.6V supply and consumes only 5mA of supply current. The MAX9720 also features thermal overload protection, and is specified over the extended -40C to +85C temperature range. The MAX9720 is available in a tiny (2mm x 2mm x 0.6mm) 16-bump chip-scale package (UCSPTM) and a 16-pin TSSOP package.
Features
o DirectDrive Eliminates Bulky DC-Blocking Capacitors o SmartSense Automatic Short Detection o Low 5mA Quiescent Current o Fixed Gain Eliminates External Feedback Network MAX9720A: -1V/V MAX9720B: -1.41V/V o 50mW per Channel Output Power o Ultra-Low 0.003% THD+N o High PSRR (92dB at 217Hz) o Integrated Click-and-Pop Suppression o 1.8V to 3.6V Single-Supply Operation o Thermal Overload Protection o Available in Space-Saving Packages 16-Bump UCSP (2mm x 2mm x 0.6mm) 16-Pin TSSOP
MAX9720
Ordering Information
PART MAX9720AEBE-T MAX9720BEBE-T MAX9720AEUE MAX9720BEUE TEMP RANGE -40oC to +85oC -40oC to +85oC -40oC to +85oC -40 C to +85 C
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PIN/BUMPPACKAGE 16 UCSP-16 16 UCSP-16 16 TSSOP 16 TSSOP
GAIN (V/V) -1 -1.41 -1 -1.41
Simplified Block Diagram
3.6V TO 1.8V SUPPLY
Applications
RIN
MAX9720
ROUT HPS MODE1 MODE2 ALERT LOUT
PDAs Cellular Phones MP3 Players Notebook PCs
Smart Phones Tablet PCs Portable Audio Equipment
+ SmartSense
SmartSense and UCSP are trademarks of Maxim Integrated Products, Inc. Pin Configuration and Typical Application Circuit appear at end of data sheet.
LIN
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
ABSOLUTE MAXIMUM RATINGS
PGND to SGND .....................................................-0.3V to +0.3V PVSS to SVSS .........................................................-0.3V to +0.3V VDD to PGND or SGND ............................................-0.3V to +4V PVSS and SVSS to PGND or SGND ..........................-4V to +0.3V IN_, OUT_, and HPS to SGND .......(SVSS - 0.3V) to (VDD + 0.3V) C1P to PGND ...............................(PGND - 0.3V) to (VDD + 0.3V) C1N to PGND .............................(PVSS - 0.3V) to (PGND + 0.3V) ALERT to PGND .......................................................-0.3V to +4V MODE_ to PGND ........................................-0.3V to (VDD + 0.3V) TIME to SGND ............................................-0.3V to (VDD + 0.3V) Output Short Circuit to GND or VDD ...............................Continuous Continuous Power Dissipation (TA = +70C) 16-Bump UCSP (derate 8.2mW/C above +70C) .......659mW 16-Pin TSSOP (derate 9.4mW/C above +70C) .......754.7mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Bump Temperature (soldering) Reflow ...........................................................................+235C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = VMODE1 = VMODE2 = 3.0V, PGND = SGND = 0V, RL = , C1 = C2 = 2.2F. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER GENERAL Supply Voltage Range Supply Current Shutdown Supply Current Turn-On/Turn-Off Time CHARGE PUMP Oscillator Frequency HEADPHONE AMPLIFIERS Voltage Gain Gain Match Total Output Offset Voltage (Note 3) Input Resistance AV AV VOS RIN 1.8V VDD 3.6V (Note 3) Power-Supply Rejection Ratio PSRR VDD = 3.0V, 200mVP-P ripple (Note 3) THD+N = 1%, fIN = 1kHz, TA = +25C DC fRIPPLE = 217Hz fRIPPLE = 1kHz fRIPPLE = 20kHz RL = 32 RL = 16 32 MAX9720A MAX9720B Between OUTL and OUTR MAX9720A MAX9720B -5 -6.5 10 76 -1.02 -1.443 -1 -1.415 1 -0.8 -1 15 92 92 86 61 50 50 mW dB +3.6 +4.5 20 -0.98 -1.386 V/V % mV k fOSC 272 320 368 kHz VDD IDD ISHDN tS Inferred from PSRR test Stereo mode Mono mode (MODE1 = VDD, MODE2 = GND) MODE1 = MODE2 = GND 1.8 5 3 6 250 10 3.6 8.4 V mA A s SYMBOL CONDITIONS MIN TYP MAX UNITS
Output Power
POUT
2
_______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(VDD = VMODE1 = VMODE2 = 3.0V, PGND = SGND = 0V, RL = , C1 = C2 = 2.2F. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Total Harmonic Distortion Plus Noise SYMBOL CONDITIONS RL = 32, POUT = 30mW RL = 16, POUT = 30mW MIN TYP 0.003 % 0.005 97 0.8 No sustained oscillations RL = 32, POUT = 1mW, fIN = 10kHz 150 75 140 15 RSMS tSMS ITIME RTIME VTIME HPS = GND 0.7 4 1 0.9 x VDD 0.7 x VDD 1 10 VALERT = VDD IOL = 3mA 0.7 x VDD 0.3 x VDD 1 A 1 0.4 A pF A V 1.1 2.4 4 3.1 1.1 1.8 10 1.2 5.6 dB V/s pF dB
o o
MAX9720
MAX
UNITS
THD+N
fIN = 1kHz
Signal-to-Noise Ratio Slew Rate Maximum Capacitive Load Crosstalk Thermal Shutdown Threshold Thermal Shutdown Hysteresis SmartSense Shorted Load Threshold Pulse Duration DEBOUNCE TIME (TIME) TIME Charging Current TIME Discharge Switch Resistance TIME Threshold
SNR SR CL
fIN = 1kHz, VOUT = 0.5VRMS, RL = 16, BW = 22Hz to 22kHz
C C
s A k V
HEADPHONE SENSE INPUT (HPS) VIH HPS Threshold VIL Input Leakage Current Input Capacitance ALERT Output Current High Output Voltage Low MODE_ INPUT VIH MODE_ Thresholds VIL MODE_ Input Leakage Current IOH VOL IIL CIN MODE1= MODE2 = GND
V
V
Note 1: All specifications are 100% tested at TA = +25oC; temperature limits are guaranteed by design. Note 2: Inputs are AC-coupled to ground. Note 3: Inputs are connected directly to ground.
_______________________________________________________________________________________
3
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
Typical Operating Characteristics
(VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9720 toc01
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9720 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
VDD = 3V AV = -1.41V/V RL = 16
MAX9720 toc03
1
VDD = 3V AV = -1V/V RL = 16
1
VDD = 3V AV = -1V/V RL = 32
1
0.1 THD+N (%) THD+N (%)
0.1 THD+N (%)
0.1
POUT = 10mW 0.01
POUT = 10mW 0.01 POUT = 40mW
POUT = 40mW 0.01
POUT = 10mW
POUT = 40mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.001 10 100 1k FREQUENCY (Hz) 10k 100k
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9720 toc04
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
VDD = 1.8V AV = -1V/V RL = 16
MAX9720 toc05
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
1 VDD = 1.8V AV = -1V/V RL = 32 0.1
MAX9720 toc06
1
VDD = 3V AV = -1.41V/V RL = 32
1
0.1 THD+N (%) THD+N (%) POUT = 10mW 0.01 POUT = 40mW
0.1 POUT = 2mW POUT = 9mW 0.01 THD + N (%)
POUT = 2mW POUT = 9mW
0.01
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001
10
100
1k FREQUENCY (Hz)
10k
100k
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9720 toc07
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX9720 toc08
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc09
1
VDD = 3V AV = -1.41V/V RL = 16
1
VDD = 3V AV = -1.41V/V RL = 32
100
10
0.1 THD+N (%) THD+N (%) POUT = 2mW POUT = 9mW 0.01
0.1 THD+N (%) 1 POUT = 2mW 0.01 0.01 POUT = 9mW
OUTPUTS IN PHASE
0.1
OUTPUTS OUT OF PHASE
VDD = 3V AV = -1V/V f = 20Hz RL = 16 60 90 120 150
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 0 30 OUTPUT POWER (mW)
4
_______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Typical Operating Characteristics (continued)
(VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.)
MAX9720
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc10
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc11
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc12
100
100
100
10
OUTPUTS IN PHASE
10
OUTPUTS IN PHASE
10
OUTPUTS IN PHASE
THD+N (%)
THD+N (%)
1 OUTPUTS OUT OF PHASE VDD = 3V AV = -1V/V f = 10kHz RL = 16 0 30 60 90 120 150
THD+N (%)
1 OUTPUTS OUT OF PHASE
1 OUTPUTS OUT OF PHASE
0.1
0.1
0.1
0.01
VDD = 3V AV = -1V/V f = 1kHz RL = 16 60 90 120 150
0.01
0.01
0.001 0 30 OUTPUT POWER (mW)
VDD = 3V AV = -1V/V f = 20Hz RL = 32 40 60 80 100
0.001 OUTPUT POWER (mW)
0.001 0 20 OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc13
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc14
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
OUTPUTS IN PHASE
MAX9720 toc15
100
100 VDD = 3V AV = -1V/V f = 10kHz RL = 32
100
10
OUTPUTS IN PHASE
10
10
OUTPUTS IN PHASE THD+N (%) 1 OUTPUTS OUT OF PHASE
THD+N (%)
1 OUTPUTS OUT OF PHASE
THD+N (%)
1 OUTPUTS OUT OF PHASE
0.1
0.1
0.1
0.01
VDD = 3V AV = -1V/V f = 1kHz RL = 32 40 60 80 100
0.01
0.01
0.001 0 20 OUTPUT POWER (mW)
0.001 0 20 40 60 80 100 OUTPUT POWER (mW)
0.001 0 30 60 90
VDD = 3V AV = -1.41V/V f = 20Hz RL = 16 120 150 OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc16
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc17
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc18
100 OUTPUTS IN PHASE
100 OUTPUTS IN PHASE
100 OUTPUTS IN PHASE
10
10
10
THD+N (%)
THD+N (%)
1
0.1
OUTPUTS OUT OF PHASE
1
THD+N (%)
0.1
OUTPUTS OUT OF PHASE
1 OUTPUTS OUT OF PHASE
0.1
0.01
0.001 0 30 60 90
VDD = 3V AV = -1.41V/V f = 1kHz RL = 16 120 150 OUTPUT POWER (mW)
0.01
0.001 0 30 60 90
VDD = 3V AV = -1.41V/V f = 10kHz RL = 16 120 150 OUTPUT POWER (mW)
0.01
VDD = 3V AV = -1.41V/V f = 20Hz RL = 32 40 60 80 100 120
0.001 0 20 OUTPUT POWER (mW)
_______________________________________________________________________________________
5
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
Typical Operating Characteristics (continued)
(VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc19
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc20
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
OUTPUTS IN PHASE 10
MAX9720 toc21
100 OUTPUTS IN PHASE
100
100
10
10
OUTPUTS IN PHASE THD+N (%)
THD+N (%)
THD+N (%)
1 OUTPUTS OUT OF PHASE
1 OUTPUTS OUT OF PHASE VDD = 3V AV = -1.41V/V f = 10kHz RL = 32 0 20 40 60 80 100 120
1 OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1V/V f = 20Hz RL = 16 0 10 20 30 40 50
0.1
0.1
0.1
0.01
VDD = 3V AV = -1.41V/V f = 1kHz RL = 32 40 60 80 100 120
0.01
0.01
0.001 0 20 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc22
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc23
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
OUTPUTS IN PHASE
MAX9720 toc24
100 OUTPUTS IN PHASE 10
100
100
10
OUTPUTS IN PHASE OUTPUTS OUT OF PHASE
10
THD+N (%)
THD+N (%)
1 OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1V/V f = 1kHz RL = 16 0 10 20 30 40 50
THD+N (%)
1
1
0.1
0.1 VDD = 1.8V AV = -1V/V f = 10kHz RL = 16 0 10 20 30 40 50
0.1
OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1V/V f = 20Hz RL = 32 0 5 10 15 20 25 30 35
0.01
0.01
0.01
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc25
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc26
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
OUTPUTS IN PHASE 10
MAX9720 toc27
100 OUTPUTS IN PHASE
100
100
10
10
OUTPUTS IN PHASE THD+N (%)
THD+N (%)
THD+N (%)
1
1 OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1V/V f = 10kHz RL = 32 0 5 10 15 20 25 30 35
1
0.1
OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1V/V f = 1kHz RL = 32 0 5 10 15 20 25 30 35
0.1
0.1
OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1.41V/V f = 20Hz RL = 16 0 10 20 30 40 50
0.01
0.01
0.01
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
6
_______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Typical Operating Characteristics (continued)
(VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.)
MAX9720
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc28
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc29
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
OUTPUTS IN PHASE
MAX9720 toc30
100 OUTPUTS IN PHASE 10
100 OUTPUTS IN PHASE OUTPUTS OUT OF PHASE
100
10
10
THD+N (%)
THD+N (%)
1
1
THD+N (%)
1
0.1
OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1.41V/V f = 1kHz RL = 16 0 10 20 30 40 50
OUTPUTS OUT OF PHASE
0.1 VDD = 1.8V AV = -1.41V/V f = 10kHz RL = 16 0 10 20 30 40 50
0.1 VDD = 1.8V AV = -1.41V/V f = 20Hz RL = 32 0 5 10 15 20 25 30 35 40
0.01
0.01
0.01
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc31
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
MAX9720 toc32
OUTPUT POWER vs. SUPPLY VOLTAGE
180 160 OUTPUT POWER (mW) 140 120 100 80 60 40 20 40 0 1.8 2.1 2.4 2.7 3.0 3.3 3.6 SUPPLY VOLTAGE (V) STEREO IN PHASE fIN = 1kHz RL = 16 THD+N = 1%
MAX9720 toc33
100 OUTPUTS IN PHASE
100 OUTPUTS IN PHASE OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1.41V/V f = 10kHz RL = 32 0 5 10 15 20 25 30 35
200 STEREO OUT OF PHASE
10
10
THD+N (%)
1
THD+N (%) 40
OUTPUTS OUT OF PHASE
1
0.1 VDD = 1.8V AV = -1.41V/V f = 1kHz RL = 32 0 5 10 15 20 25 30 35
0.1
0.01
0.01
0.001 OUTPUT POWER (mW)
0.001 OUTPUT POWER (mW)
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9720 toc34
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9720 toc35
OUTPUT POWER vs. SUPPLY VOLTAGE
140 OUTPUT POWER (mW) 120 100 80 60 40 20 0 STEREO IN PHASE fIN = 1kHz RL = 32 THD+N = 10% STEREO OUT OF PHASE
MAX9720 toc36
200 180 160 OUTPUT POWER (mW) 140 120 100 80 60 40 20 0 1.8 2.1 2.4 2.7 3.0 3.3 STEREO IN PHASE fIN = 1kHz RL = 16 THD+N = 10% STEREO OUT OF PHASE
160 140 OUTPUT POWER (mW) 120 100 80 60 40 20 0 STEREO IN PHASE fIN = 1kHz RL = 32 THD+N = 1%
160
STEREO OUT OF PHASE
3.6
1.8
2.1
2.4
2.7
3.0
3.3
3.6
1.8
2.1
2.4
2.7
3.0
3.3
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
7
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
Typical Operating Characteristics (continued)
(VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.)
OUTPUT POWER vs. LOAD RESISTANCE
MAX9720 toc37
OUTPUT POWER vs. LOAD RESISTANCE
MAX9720 toc38
OUTPUT POWER vs. LOAD RESISTANCE
35 OUTPUT POWER (mW) 30 25 20 15 10 5 0 INPUTS IN PHASE INPUTS OUT OF PHASE VDD = 1.8V f = 1kHz THD+N = 1%
MAX9720 toc39
160 140 OUTPUT POWER (mW) 120 100 80 60 40 20 0 10 LOAD RESISTANCE () INPUTS IN PHASE INPUTS OUT OF PHASE f = 1kHz THD+N = 1%
160 140 OUTPUT POWER (mW) 120 100 80 60 40 20 0 INPUTS IN PHASE INPUTS OUT OF PHASE f = 1kHz THD+N = 10%
40
100
10 LOAD RESISTANCE ()
100
10 LOAD RESISTANCE ()
100
OUTPUT POWER vs. LOAD RESISTANCE
35 OUTPUT POWER (mW) 30 25 20 15 10 5 0 10 LOAD RESISTANCE () 100 INPUTS IN PHASE INPUTS OUT OF PHASE VDD = 1.8V f = 1kHz THD+N = 10%
MAX9720 toc40
POWER DISSIPATION vs. OUTPUT POWER
MAX9720 toc41
POWER DISSIPATION vs. OUTPUT POWER
MAX9720 toc42
40
350 300 POWER DISSIPATION (mW) RL = 16 250 200 150 100 50 0 0 50 100 150 200 RL = 32 VDD = 3V f = 1kHz POUT = POUTL + POUTR
125
POWER DISSIPATION (mW)
100
RL = 16
75
50 RL = 32 25 VDD = 1.8V f = 1kHz POUT = POUTL + POUTR 0 20 40 60 80
0 250 OUTPUT POWER (mW) OUTPUT POWER (mW)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX9720 toc43
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX9720 toc44
CROSSTALK vs. FREQUENCY
VDD = 3V RL = 32 VIN = 200mVP-P
MAX9720 toc45
0 -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 -110 -120 10 100 1k FREQUENCY (Hz) 10k VDD = 3V VRIPPLE = 200mVP-P
0 -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 VDD = 1.8V VRIPPLE = 200mVP-P
0 -10 -20 CROSSTALK (dB) -30 -40 -50 -60 -70 -80 -90 -100 -110 -120
RIGHT-TO-LEFT CHANNEL
LEFT-TO-RIGHT CHANNEL 10 100 1k FREQUENCY (Hz) 10k 100k
100k
10
100
1k FREQUENCY (Hz)
10k
100k
8
_______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Typical Operating Characteristics (continued)
(VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.)
CHARGE-PUMP OUTPUT IMPEDANCE vs. SUPPLY VOLTAGE
MAX9720 toc47 MAX9720 toc48
MAX9720
CROSSTALK vs. FREQUENCY
-10 -20 -30 CROSSTALK (dB) -40 -50 -60 -70 -80 -90 -100 -110 -120 10 100 1k FREQUENCY (Hz) 10k 100k VDD = 1.8V RL = 32 VIN = 200mVP-P
MAX9720 toc46
GAIN FLATNESS vs. FREQUENCY
5 4 3 2 GAIN (dB) 1 0 -1 -2 AV = -1V/V 14 12 OUTPUT IMPEDANCE () 10 8 6 4 2
0
RIGHT-TO-LEFT CHANNEL
LEFT-TO-RIGHT CHANNEL
-3 -4 -5 0.01 0.1 1 10 100 1k 10k FREQUENCY (Hz) ILOAD = 10mA 0 1.8 2.1 2.4 2.7 3.0 3.3 3.6 SUPPLY VOLTAGE (V)
OUTPUT POWER vs. LOAD RESISTANCE AND CHARGE-PUMP CAPACITOR SIZE
MAX9720 toc49
OUTPUT SPECTRUM vs. FREQUENCY
MAX9720 toc50
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9720 toc51
60 2.2F 50 OUTPUT POWER (mW) 1F 40 30 0.47F 20 10 0 10 20 30 40 fIN = 1kHz THD+N = 1% OUTPUTS IN PHASE
0 -20 OUTPUT SPECTRUM (dB) -40 -60 -80 -100 -120 VIN = 1VP-P RL = 32 fIN = 1kHz
6 5 SUPPLY CURRENT (mA) STEREO MODE 4 3 MONO MODE 2 1 0
50
100
1k
10k
100k
1.8
2.1
2.4
2.7
3.0
3.3
3.6
LOAD RESISTANCE ()
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9720 toc52
EXITING SHUTDOWN
MAX9720 toc53
POWER-UP/DOWN WAVEFORM
MAX9720 toc54
9 8 SUPPLY CURRENT (A) 7 6 5
3V MODE1 AND MODE2 3V 0V 100dB OUT_ 10mV/div VDD 0V
4 3 2 1 0 1.8 2.1 2.4 2.7 3.0 3.3 3.6 fIN = 1kHz RL = 32 400s/div VIN = GND RL = 32 SUPPLY VOLTAGE (V) 200ms/div FFT: 25Hz/div OUT_FFT OUT_ 500mV/div 20dB/div
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9
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
Pin Description
PIN TSSOP 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 BUMP UCSP D2 C2 D1 C1 B1 A1 B2 A2 A3 B3 A4 B4 C4 D4 C3 D3 NAME VDD MODE1 C1P PGND C1N PVSS MODE2 ALERT INL TIME INR SGND SVSS OUTR HPS OUTL Positive Power Supply Mode Select 1 Logic Input Flying Capacitor Positive Terminal Power Ground. Connect to SGND. Flying Capacitor Negative Terminal Charge-Pump Output Mode Select 2 Logic Input Open-Drain Interrupt Logic Output Left-Channel Audio Input Debouncing Timer Capacitor Right-Channel Audio Input Signal Ground. Connect to PGND. Amplifier Negative Power Supply. Connect to PVSS. Right-Channel Output Headphone Sense Input Left-Channel Output FUNCTION
Detailed Description
The MAX9720 fixed-gain, stereo headphone amplifier includes Maxim's patented DirectDrive architecture and SmartSense. DirectDrive eliminates the large outputcoupling capacitors required by conventional singlesupply headphone amplifiers. SmartSense automatically detects the presence of a short at either output. Under a fault condition, the shorted output is automatically disabled and the stereo input signal is automatically mixed and routed to the remaining active channel. This prevents damage to the amplifier and optimizes power savings by eliminating battery drain into a shorted load. The device consists of two 50mW Class AB headphone amplifiers, an internal feedback network (MAX9720A: fixed -1V/V gain, MAX9720B: fixed -1.41V/V gain), a mono mixer/attenuator, undervoltage lockout (UVLO)/ shutdown control, SmartSense, a charge pump, and comprehensive click-and-pop suppression circuitry (see Functional Diagram). The charge pump inverts the positive supply (V DD ), creating a negative supply (PVSS). The headphone amplifiers operate from these bipolar supplies with their outputs biased about GND (Figure 1). The amplifiers have almost twice the supply range compared to other single-supply amplifiers, nearly quadrupling the available output power. The benefit of the GND bias is that the amplifier outputs do not have a DC component (typically VDD/2). This elimi10
nates the large DC-blocking capacitors required with conventional headphone amplifiers, conserving board space, system cost, and improving frequency response. The noninvasive SmartSense feature of the MAX9720 detects a short on either output. The SmartSense routine executes when the device is powered up or brought out of shutdown (see the SmartSense section). If a fault is detected, the shorted channel is shut down, the output goes high impedance, and the stereo audio input is mixed/attenuated and fed to the remaining active channel. The device also features an ALERT output that indicates to a host C that SmartSense has detected a short-circuit condition on either amplifier output. Forced stereo and forced mono modes can also be selected through the two MODE_ inputs. In forced operation mode, SmartSense is disabled and the device operates as specified by the MODE_ inputs, regardless of output load conditions. A fast low-power shutdown mode is also selected through the MODE_ inputs (see the Mode_ Selection section). The UVLO prevents operation from an insufficient power supply and click-and-pop suppression, which eliminates audible transients on startup and shutdown. Additionally, the MAX9720 features thermal overload protection and can withstand 4kV ESD strikes on the output.
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50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor sizes.
VDD VOUT VDD/2 GND
MAX9720
CONVENTIONAL DRIVER-BIASING SCHEME
+VDD
Previous attempts to eliminate the output-coupling capacitors involved biasing the headphone return (sleeve) to the DC bias voltage of the headphone amplifiers. This method raised some issues: * The sleeve is typically grounded to the chassis. Using this biasing approach, the sleeve must be isolated from system ground, complicating product design. * During an ESD strike, the amplifier's ESD structures are the only path to system ground. The amplifier must be able to withstand the full ESD strike. * When using the headphone jack as a line out to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equipment, resulting in large ground-loop current and possible damage to the amplifiers. * When using a combination microphone and speaker headset (in a cell phone or PDA application), the microphone typically requires a GND return. Any DC bias on the sleeve conflicts with the microphone requirements (Figure 2).
VOUT
GND
-VDD
DirectDrive BIASING SCHEME
Figure 1. Conventional Amplifier Output Waveform vs. MAX9720 Output Waveform
DirectDrive
Conventional single-supply headphone amplifiers have their outputs biased about a nominal DC voltage (typically half the supply) for maximum dynamic range. Large coupling capacitors are needed to block this DC bias from the headphone. Without these capacitors, a significant amount of DC current flows to the headphone, resulting in unnecessary power dissipation and possible damage to both headphone and headphone amplifier. Maxim's patented DirectDrive architecture uses a charge pump to create an internal negative supply voltage. This allows the MAX9720 output to be biased about GND, almost doubling dynamic range while operating from a single supply. With no DC component, there is no need for the large DC-blocking capacitors. Instead of two large capacitors (220F typ), the MAX9720 charge pump requires only two, small ceramic capacitors (1F typ), conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. See the Output Power vs.
Low-Frequency Response In addition to the cost and size disadvantages, the DCblocking capacitors limit the low-frequency response of the amplifier and distort the audio signal: * The impedance of the headphone load and the DCblocking capacitor form a highpass filter with the -3dB point determined by: f-3dB = 1 2RLCOUT
where R L is the impedance of the headphone and COUT is the value of the DC-blocking capacitor. The highpass filter is required by conventional singleended, single-supply headphone amplifiers to block the midrail DC component of the audio signal from the headphones. Depending on the -3dB point, the filter can attenuate low-frequency signals within the audio band. Larger values of COUT reduce the attenuation, but are physically larger, more expensive capacitors. Figure 3 shows the relationship between the size of COUT and the resulting low-frequency attenuation. Note that the -3dB point for a 16 headphone with a 100F blocking capacitor is 100Hz, well within the audio band.
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11
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
* The voltage coefficient of the capacitor, the change in capacitance due to a change in the voltage across the capacitor, distorts the audio signal. At frequencies around the -3dB point, the reactance of the capacitor dominates, and the voltage coefficient appears as frequency-dependent distortion. Figure 4 shows the THD+N introduced by two different capacitor dielectrics. Note that around the -3dB point, THD+N increases dramatically.
SmartSense
The SmartSense feature detects a short on either output and automatically reconfigures the MAX9720 for optimum power savings. If an output short circuit is detected during the SmartSense routine, the shorted channel is disabled, ALERT is asserted, and the device is set to mono mode (assuming the other channel is not shorted). SmartSense works by applying an inaudible 3s test voltage pulse to the load. The resulting current from the test pulse and load is sensed. If the load impedance is less than 4, the output is determined to be a short.
LOW-FREQUENCY ROLLOFF (RL = 16)
0 -3 -6 ATTENUATION (dB) -9 -12 -15 -18 -21 -24 -27 -30 0.01 0.1 1 FREQUENCY (Hz) 10 100 33F DirectDrive 330F 220F 100F
The combination of low-frequency attenuation and frequency-dependent distortion compromises audio reproduction. DirectDrive improves low-frequency reproduction in portable audio equipment that emphasizes low-frequency effects such as multimedia laptops and MP3, CD, and DVD players. Charge Pump The MAX9720 features a low-noise charge pump. The 320kHz switching frequency is well beyond the audio range, and does not interfere with the audio signals. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. Limiting the switching speed of the charge pump minimizes the di/dt noise caused by the parasitic bond wire and trace inductance. Although not typically required, additional high-frequency ripple attenuation can be achieved by increasing the size of C2 (see Typical Application Circuit).
MICROPHONE BIAS MICROPHONE AMPLIFIER MICROPHONE AMPLIFIER OUTPUT
Figure 3. Low-Frequency Attenuation of Common DC-Blocking Capacitor Values ADDITIONAL THD+N DUE TO DC-BLOCKING CAPACITORS
10
AUDIO INPUT THD+N (%)
1
0.1 TANTALUM 0.01
AUDIO INPUT
MAX9720
0.001 ALUM/ELEC 0.0001 HEADPHONE DRIVER 10 100 1k FREQUENCY (Hz) 10k 100k
Figure 2. Earbud Speaker/Microphone Combination Headset Configuration 12
Figure 4. Distortion Contributed by DC-Blocking Capacitors
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50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Mode Selection (MODE_) SmartSense is controlled by the two mode select inputs, MODE1 and MODE2. Table 1 shows the operating modes in relation to the status of the MODE_ inputs. When MODE1 = MODE2 = low, the device is in lowpower shutdown mode. When MODE1 = high and MODE2 = low, the device is in forced mono mode. The right channel is disabled, OUTR goes high impedance, and the stereo audio input is mixed, and the audio signal is reproduced on OUTL. SmartSense is disabled in this mode. When MODE1 = low and MODE2 = high, the device is in forced stereo mode, and SmartSense is disabled. When the device detects the presence of a short BEFORE forced stereo mode is selected, the device remains in mono mode (Figure 5). When MODE1 = MODE2 = high, the device is in automatic detection mode; the operating mode of the device is determined by SmartSense. MODE1 is also used to execute a host-controlled SmartSense routine and reset the ALERT output. On the rising edge of MODE1, the device invokes a SmartSense routine. The falling edge of MODE1 resets the ALERT output to its idle state. Automatic Detection Mode A fault condition is defined as a short (under 4) on either amplifier output to ground. SmartSense automatically detects and disables the shorted output. The mixer/attenuator combines the two stereo inputs (INL and INR), attenuates the resultant signal by a factor of 2, and redirects the audio playback to the remaining active channel. This allows for full reproduction of a stereo signal through a single headphone while maintaining optimum headroom. The mixed mono signal is output only on the properly loaded channel. If both outputs are shorted then both outputs go into a highimpedance state and no audio playback occurs. In automatic detection mode (MODE1 = MODE2 = high), any of the following events trigger a SmartSense test sequence: * HPS rises above 0.8 x VDD, indicating a headphone jack has been inserted into the socket. * The 180mA high-side (sourcing) overcurrent threshold is approached, and the output is near GND. * The die temperature exceeds the thermal limit (+140C). * Power or shutdown is cycled.
MAX9720
MAX9720
SmartSense
M1 = L M2 = L ? N
Y
SHDN
N
STATUS CHANGE ? FORCED MONO
Y
M1 = H M2 = L ? N
Y
N
STATUS CHANGE ? FORCED STEREO
Y
M1 = L M2 = H ? N
Y
N
Table 1. MAX9720 Operating Modes
MODE1 High Low High Low MODE2 High Low Low High High X SmartSense Enabled Disabled Disabled Disabled Enabled -- OPERATING MODE Automatic detection mode Shutdown Forced left mono Forced stereo Host controlled Reset ALERT
N STATUS CHANGE ? Y SHORT DETECTED ? N Y
STATUS CHANGE ? MONO MODE
Y
STEREO MODE
N
STATUS CHANGE ?
Y
Figure 5. SmartSense Flow Diagram ______________________________________________________________________________________ 13
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
For automatic headphone detection, connect HPS to the control pin of a 3-wire headphone jack, as shown in Figure 7. With no headphone present, the output impedance of the amplifier pulls HPS to less than 0.8 x VDD. When a headphone plug is inserted into the jack, the control pin is disconnected from the tip contact, and HPS is pulled to VDD through the internal 100k pullup. A debounce delay controls the time between HPS going high and the initiation of the SmartSense test sequence. This time is controlled by an external capacitor on the TIME pin and allows the user to customize the debounce time (see the TIME Capacitor section). Shutdown Driving MODE1 and MODE2 to GND shuts down the MAX9720, disconnects the internal HPS pullup resistor, disables the charge pump and amplifiers, sets the amplifier output impedance to 1k, and reduces supply current to less than 6A. Forced Mono Mode In forced left mono mode (MODE1 = high, MODE2 = low), the right channel is disabled and OUTR goes high impedance. The stereo signal inputs are combined through the mixer/attenuator and output on the left channel. In forced mono mode, the SmartSense routine is disabled. Forced Stereo Mode In forced stereo mode (MODE1 = low, MODE2 = high), the device operates as a stereo headphone amplifier. In forced stereo mode, the SmartSense routine is disabled. ALERT Output The MAX9720 includes an active-low, open-drain ALERT output that indicates to the master device that SmartSense has detected a fault condition. ALERT triggers when an output short circuit is detected through the SmartSense routine. During normal operation, ALERT idles high. If a fault condition is detected, ALERT pulls the line low. ALERT remains low until MODE1 is toggled from high to low.
MAX9720
TIP (SIGNAL)
SLEEVE (GND)
Figure 6. Typical 2-Wire (Mono) Headphone Plug
VDD
MAX9720
R1 100k HPS OUTL OUTR 15 16 14
Figure 7. HPS Configuration
Click-and-Pop Suppression
In conventional single-supply audio amplifiers, the output-coupling capacitor is a major contributor of audible clicks and pops. Upon startup, the amplifier charges the coupling capacitor to its bias voltage, typically half the supply. Likewise, during shutdown, the capacitor is discharged to GND. A DC shift across the capacitor results, which in turn appears as an audible transient at the speaker. Since the MAX9720 does not require output-coupling capacitors, no audible transient occurs.
Additionally, the MAX9720 features extensive click-andpop suppression that eliminates any audible transient sources internal to the device. The Power-Up/Down Waveform in the Typical Operating Characteristics shows that there are minimal spectral components in the audible range at the output upon startup and shutdown. In most applications, the preamplifier output driving the MAX9720 has a DC bias of typically half the supply. During startup, the input-coupling capacitor is charged to the preamplifier's DC bias voltage through the input resistor of the MAX9720, resulting in a DC shift across the capacitor and an audible click/pop. Delaying the startup of the MAX9720 by 4 to 5 time constants (80ms to 100ms) based on RIN and CIN, relative to the startup of the preamplifier, eliminates this click/pop caused by the input filter. If the SmartSense routine occurs during normal operation, a low-level audible transient may be heard. To prevent this, a host-controlled SmartSense routine should only be executed when ALERT asserts.
14
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50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Applications Information
Power Dissipation
Under normal operating conditions, linear power amplifiers can dissipate a significant amount of power. The maximum power dissipation for each package is given in the Absolute Maximum Ratings section under Continuous Power Dissipation or can be calculated by the following equation: TJ(MAX) - TA PDISSPKG(MAX) = JA where TJ(MAX) is +150C, TA is the ambient temperature, and JA is the reciprocal of the derating factor in C/W as specified in the Absolute Maximum Ratings section. For example, JA of the TSSOP package is +106.38C/W. The MAX9720 has two power dissipation sources: the charge pump and the two amplifiers. If the power dissipation for a given application exceeds the maximum allowed for a given package, either reduce VDD, increase load impedance, decrease the ambient temperature, or add heat sinking to the device. Large output traces improve the maximum power dissipation in the package. Thermal overload protection limits total power dissipation in the MAX9720. When the junction temperature exceeds +140C, the thermal protection circuitry disables the amplifier output stage. The amplifiers are enabled once the junction temperature cools by 15C, resulting in a pulsing output under continuous thermal overload conditions. Output Power The MAX9720 is specified for the worst-case condition--when both inputs are in phase. Under this condition, the amplifiers simultaneously draw current from the charge pump, leading to a slight loss in headroom of VSS. In typical stereo audio applications, the left and right signals present differences in both magnitude and phase, subsequently leading to an increase in the maximum attainable output power. Figure 8 shows the two extreme cases for in- and out-of-phase. In reality, the available power lies between these extremes.
100 OUTPUTS IN PHASE OUTPUTS OUT OF PHASE SINGLECHANNEL VDD = 3V AV = -1V/V f = 1kHz RL = 16 0 20 40 60 80 100 120 140 160
MAX9720
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER
10 THD+N (%)
1
0.1
0.01
0.001 OUTPUT POWER (mW)
Figure 8. THD+N vs. Output Power with Inputs In-/Out-of-Phase
The charge-pump voltage at PVSS is roughly proportional to VDD and is not a regulated voltage. Consider the charge-pump output impedance when powering other devices from PVSS. See the Charge-Pump Output Impedance graph in the Typical Operating Characteristics. Use 2.2F charge-pump capacitors for the highest output power; 1F or lower capacitors can also be used for most applications. See the Output Power vs. Load Resistance and Charge-Pump Capacitance graph for details of the output power vs. capacitor size.
Component Selection
Input Filtering The input capacitor (C IN ), in conjunction with the MAX9720 input impedance, forms a highpass filter that removes the DC bias from an incoming signal (see Typical Application Circuit). The AC-coupling capacitor allows the amplifier to bias the signal to an optimum DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is given by: f-3dB = 1 2RINCIN
Powering Other Circuits from a Negative Supply
An additional benefit of the MAX9720 is the internally generated, negative supply voltage (PVSS). PVSS is the negative supply for the MAX9720 headphone amplifiers. PVSS can power other devices within a system. Limit the current drawn from PVSS to 5mA. Exceeding this affects the operation of the headphone amplifiers. A typical application is a negative supply to adjust the contrast of LCD modules.
RIN is the amplifier's internal input impedance value given in the Electrical Characteristics. Chose CIN such that f-3dB is well below the lowest frequency of interest. Setting f-3dB too high affects the amplifier's low-frequency response. Use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies.
15
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50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
Table 2. Suggested Capacitor Manufacturers
SUPPLIER Taiyo Yuden TDK PHONE 800-348-2498 847-803-6100 FAX 847-925-0899 847-390-4405 www.t-yuden.com www.component.tdk.com WEBSITE
Charge-Pump Capacitor Selection Use capacitors with an ESR less than 100m for optimum performance. Low-ESR ceramic capacitors minimize the output resistance of the charge pump. For best performance over the extended temperature range, select capacitors with an X7R dielectric. Table 2 lists suggested manufacturers. Flying Capacitor (C1) The value of the flying capacitor (C1) affects the charge pump's load regulation and output impedance. A C1 value that is too small degrades the device's ability to provide sufficient current drive, which leads to a loss of output voltage. In most applications, 1F for both C1 and C2 provides adequate performance. Increasing the value of C1 improves load regulation and reduces the charge-pump output resistance to an extent. See the Output Power vs. Charge Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics. Above 2.2F, the on-resistance of the switches and the ESR of C1 and C2 dominate. Hold Capacitor (C2) The hold capacitor value and ESR directly affect the ripple on PVSS. Increasing the value of C2 reduces output ripple. Likewise, decreasing the ESR of C2 reduces both ripple and output impedance. Lower capacitance values can be used in systems with low maximum output power levels. See the Output Power vs. ChargePump Capacitance and Load Resistance graph in the Typical Operating Characteristics. Power-Supply Bypass Capacitor The power-supply bypass capacitor (C3) lowers the output impedance of the power supply and reduces the impact of the MAX9720's charge-pump switching transients. Bypass VDD with C3, the same value as C1, and place it physically close to the device.
TIME Capacitor The TIME capacitor (CTIME) sets the HPS debounce time. The debounce time is the delay between HPS exceeding 0.8 x V DD and the execution of the SmartSense routine. The delay ensures that any excessive contact bounce caused by the insertion of a headphone plug into the jack does not cause HPS to register an invalid state (Figure 9). The value of the CTIME in nF equals the nominal delay time in ms, i.e., CTIME = 10nF = tDELAY = 10ms. CTIME values in the 200nF to 600nF range are recommended.
Adding Volume Control
The addition of a digital potentiometer provides simple, digital volume control. Figure 10 shows the MAX9720 with the MAX5408 dual log taper digital potentiometer used as an input attenuator. Connect the high terminal of the MAX5408 to the audio input, the low terminal to GND, and the wiper to CIN. Setting the wiper to the top position passes the audio signal unattenuated. Setting the wiper to the lowest position fully attenuates the input.
Layout and Grounding
Proper layout and grounding are essential for optimum performance. Connect PGND and SGND together at a single point on the PC board. Connect all components associated with the charge pump (C2 and C3) to the PGND plane. Connect PVSS and SVSS together at the device. Bypassing of both the positive and negative supplies is accomplished by the charge-pump capacitors, C2 and C3 (see Typical Application Circuit). Place capacitors C1 and C3 as close to the device as possible. Place capacitor C2 as close to PVSS as possible. Route PGND and all traces that carry switching transients away from SGND, traces, and components in the audio signal path.
16
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50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
HEADPHONE INSERTED HPS
LEFT AUDIO 5 H0 INPUT CIN W0A 7 6 L0 9 INL OUTL 16
tDELAY 3.1s
RIGHT AUDIO 12 H1 INPUT
MAX5408
MAX9720
CIN W1A 10 11 INR OUTR 14
70mV OUT_
11 L1
Figure 9. HPS Debouncing Delay
Figure 10. MAX9720 and MAX5408 Volume Control Circuit
Pin Configurations
TOP VIEW
VDD 1 MODE1 2 C1P 3 PGND 4 C1N 5 PVSS 6 MODE2 7 ALERT 8 16 OUTL 15 HPS 14 OUTR
UCSP Applications Information
For the latest application details on UCSP construction, dimensions, tape carrier information, printed circuit board techniques, bump-pad layout, and the recommended reflow temperature profile, as well as the latest information on reliability testing results, go to Maxim's website at www.maxim-ic.com/ucsp and look up Application Note: UCSP--A Wafer-Level Chip-Scale Package.
MAX9720
13 SVSS 12 SGND 11 INR 10 TIME 9 INL
Chip Information
TRANSISTOR COUNT: 4858 PROCESS: BiCMOS
TSSOP TOP VIEW (BUMP SIDE DOWN)
A PVSS ALERT B C1N MODE2 TIME SGND C PGND MODE1 HPS D C1P VDD OUTL OUTR SVSS INL INR 1 2 3 4
UCSP
______________________________________________________________________________________
17
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
System Diagram
VDD VDD 0.1F AUX_IN 0.1F 15k 2.2k BIAS 2.2k 0.1F IN+ IN0.1F MODE1 MODE2 VDD 1F INL 10k 1F ALERT TIME 220nF C1P CIN PVSS SVSS 1F INR VDD HPS 1F OUT SHDN VDD 100k 0.1F 15k
MAX4063 OUT
CODEC/ BASEBAND PROCESSOR 0.1F 15k 1F
IN VDD BIAS
OUT+ OUT-
MAX4365
MAX9720 OUTL
OUTR
C
1F
18
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50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Typical Application Circuit
MAX9720
1.8V TO 3.8V
LOGIC CONTROL R4 10k
C3 1F 1 (D2) VDD 2 (C2) MODE1
7 (B2) MODE2
8 (A2) ALERT
LEFTCHANNEL AUDIO INPUT
CIN 1F 9 (A3) INL
MAX9720
MIXER ATTENUATOR AND GAIN SETTING VDD 16 (D3)
OUTL UVLO AND SHUTDOWN CONTROL SGND SVSS R1 100k HPS SmartSense AND HEADPHONE DETECTION VDD
3 (D1) C1P
15 (C3)
C1 1F 5 (B1) C1N
CHARGE PUMP
CLICK-AND-POP SUPPRESSION
VDD SGND OUTR MIXER ATTENUATOR AND GAIN SETTING PVSS 6 (A1) C2 1F SVSS 13 (C4) PGND 4 (C1) SGND 12 (B4) TIME 10 (B3) C4 220nF CIN 1F INR 11 (A4) 14 (D4)
SVSS
RIGHTCHANNEL AUDIO INPUT ( ) UCSP BUMP.
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19
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
16L,UCSP.EPS
20
______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX9720
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 21 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
TSSOP4.40mm.EPS

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