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SP6682 High Efficiency Charge Pump Regulator for White LEDs
FEATURES Ideal For White LED Driver Low Profile, Inductorless Regulator Output Current up to 200mA X1.5 and X2 Modes for Highest Efficiency +2.7V to +5.5V Input Voltage Range Fast Turn-On Time, 175S 1mA Quiescent Current <1.5A Shutdown Current 600kHz Oscillator Programmable Output Current or Voltage PWM Dimming Control with Enable Pin Shutdown to Disconnect Output from Input Soft Start to Eliminate In-Rush Current Industry Standard 10-pin MSOP Package and Small 10-pin DFN Package
V OUT C1P V IN V MODE FB
1 2 3 4 5
10
C2P C1N GND C2N EN/PWM
SP6682
10 Pin DFN
9 8 7 6
Now Available in Lead Free Packaging
APPLICATIONS Next Generation Mobile Phones PDAs 3.3V to 5.0V Conversion Palmtop Computers Color LCD Modules DESCRIPTION The SP6682 is a current regulated charge pump ideal for converting a Li-Ion battery input for driving white LEDs used in backlighting color displays or cell phone camera flash applications. The charge pump automatically switches between X1.5 and X2 modes based on the programmable VMODE voltage, providing improved efficiency over traditional methods using charge pump doubler followed by LDO. This input voltage threshold can be externally programmed by a resistor divider network for optimized efficiency at specific output voltages and currents. The SP6682 operates with an internal 600kHz clock, which reduces switching noise and improves VOUT ripple. Output current or voltage can be accurately regulated by modulating the switcher between the charge pump and output capacitor. In shutdown mode, the IC disconnects the output from the input and draws less than 1.5A current. The SP6682 is offered in a 10-pin MSOP package, and a small 10-Pin DFN Package. TYPICAL APPLICATION SCHEMATIC
LCD BACKLIGHT APPLICATION
2.7 - 4.2V C6 0.1F
C2 2.2F
(R)
Lithium-Ion
C1 2.2F
C2P 10 SP6682 C1N 9 3 8 VIN GND 4 7 VMODE C2N 5 6 FB EN/PWM
1V OUT 2 C1P
C4 2.2F C5 2.2F
White LED
R6 20
R3 1M
20
20
20
ENABLE/PWM DIMMING
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
1
TYPICAL APPLICATION SCHEMATIC
Iout=200mA for 1W LED
CAMERA FLASH APPLICATION
Vin: 3.0-4.2V
SP6682
1 Vout
2 C1P
3 Vin
GND
C1N
C2P 10
LEDA
9
8
C4 2.2uF
1W LED
4 Vmode 5 C2N FB EN/PWM
7 6
C1 2.2uF
R3 1.0M
C5 2.2uF
LEDK
VFB=300mV
Rfb 1.5 Ohm
ENABLE/PWM
ABSOLUTE MAXIMUM RATINGS
VIN, VMODE, VOUT and EN/PWM ................. -0.3V to 6V VIN - VOUT ........................................................... 0.7V Output Current (IOUT) ...................................... 300mA Power Dissipation per Package - 10-pin MSOP (derate 8.84mW/C above +70C) ................. 720mW Junction Temperature .................................... +125C Storage Temperature ...................... -65C to +150C ESD Rating. ................................................ 2kV HBM
These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
ELECTRICAL CHARACTERISTICS
Unless otherwise specified: VIN =+2.7V to +5.0V, C1=C2=C4=C5=2.2F (ceramic, ESR=0.03), C3=0.1F (ceramic) and TAMB =-40C to +85C unless otherwise noted.
PARAMETER MIN TYP MAX UNITS CONDITIONS
Input Voltage
2.7
5.5
V
Quiescent Current
1.2
3
mA
VIN = 4.2V, VOUT = 3.6V, IOUT = 100A
Shutdown Current
1.5
A
EN/PWM = 0.0V, VIN = 5.5V
Oscillator Frequency
0.42
0.60
0.78
MHz
VIN = 3.6V
VFB Reference Voltage
0.275
0.306
0.337
V
Charge Pump Output Resistance
11
18
FB = 0.0V, VIN = 3.6V, IOUT = 20mA, VMODE = High
VMODE Threshold Voltage
1.15
1.25
1.35
V
VIN Falling @ 25C
Hysteresis for Mode Transition Voltage
30
mVPP
VIN = 3.6V @ 25C
VMODE Pin Current
0.01
0.5
A
VMODE = 1.25
EN/PWM Logic Low
0.4
V
EN/PWM Logic High
EN/PWM Pin Current
FB Pin Current
1.6
0.01
175
V
0.5
0.5
A
A
VEN/PWM = 4.2V
VFB = 1V
VOUT Turn-On Time
500
s
VIN = 3.6V, FB within 90% regulation
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
2
PERFORMANCE CHARACTERISTICS
Refer to the typical application circuit, TAMB = 25 C, IO = 60mA unless otherwise specified.
O
EN/PWM
5V/DIV 1V/DIV
90 80 70 60 50 40 30 20 10 0 2.7 3 3.3 3.6 3.9 4.2
VOUT
Efficiency (%)
Input Voltage(V)
Figure 1. Output voltage turn-on time
Figure 2. Power efficiency vs. input voltage
VIN
50mV/DIV
0.34 0.33 0.32
VFB (V)
0.31 0.3 0.29 0.28 0.27 0.26 2.7 3 3.3 VIN (V) 3.6 3.9 4.2
VOUT
50mV/DIV
Figure 3. X2 mode voltage ripple when VIN = 2.7V
Figure 4. Feedback pin voltage vs. input voltage
VIN
50mV/DIV
1 0.9 0.8
ISUPPLY (mA)
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2.7 3 3.3 VIN (V) 3.6 3.9 4.2
VOUT
50mV/DIV
Figure 5. X1.5 mode voltage ripple when VIN = 3.3V
Date: 7/19/06 Rev D
Figure 6. Quiescent current vs. input voltage
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
3
PERFORMANCE CHARACTERISTICS: Continued
Refer to the typical application circuit, TAMB = 25C, IO = 60mA unless otherwise specified.
6 5
Brightness (kcd/m2)
3
Brigtness, kCd/m2
100 Hz
500 Hz
4 3 2 1 0 2.7
2
1
3
3.3
3.6
3.9
4.2
0
Input Voltage (V)
0
20
40
60
80
100
Duty Cycle,%
4 LED's @ 30mA
4 LED's @ 15mA
Figure 7. Brightness vs. input voltage
Figure 8. Brightness vs. duty cycle
SP6682 IOUT vs VIN 250 200 IOUT (mA) 150
SP6682 Luxeon I, VF = 3.2V
100 50 0 3.0 3.2 3.4 3.6 VIN (V) 3.8 4.0 4.2
Figure 9. IOUT vs. VIN
Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs (c) 2006 Sipex Corporation
4
OPERATION GENERAL OVERVIEW The SP6682 is a current regulated charge pump ideal for converting a Li-Ion battery input for driving white LEDs used in backlighting color displays, Cell Phone Camera Flash, PDAs, digital cameras and MP3 players. The SP6682s proprietary AutoBoost feature enables the IC to automatically transition from X1.5 boost mode to X2 boost mode based on battery input voltage for optimal efficiency and performance. The SP6682 is able to efficiently drive up to six 20mA white LEDs in parallel and maintain a constant brightness over a very wide operating voltage range (2.7V to 5.5V). The SP6682 operates with an internal 600kHz clock, enabling the use of small external components. Other features of SP6682 include PWM dimming control as well as complete input/out disconnect in shutdown. In shutdown mode the IC draws less than 1.5A current. The output regulation is achieved by sensing the voltage at the feedback pin and modulating the switcher between the charge pump and output capacitor. an input voltage to the mode comparator which sets the logic state of the mode selection outputs to the X2 or X1.5 modes. VMODE is compared to a 1.25V bandgap voltage. For example, if one makes a 158K/100K divider, the mode will change at 2.58 x 1.25 V = 3.23V. A comparator-based cycle-bycycle regulation ensures that no mode change occurs during cycles. 3) Clock Manager. An internal 600 kHz clock is generated in this block. Depending on the mode control, the appropriate clock phasing is generated here and sent to the start-up and charge-pump switches block. 4) Start-up and Charge Pump Switches. During start-up, until the reference is established, this block keeps the charge pump inactive. During this period the output stays floating, and by consequence the charge pump drivers are now referenced to VOUT. Charging of the output will occur (e.g. when VIN is ramped up to 4.2V, VOUT ramps only up to about 3V), but not to the value of VIN, protecting the White LEDs from experiencing high input voltages. Another important operation of this block is the PWM/EN dimming control, which is implemented in the delay of each pump driver, so that the enable high pulse width is proportional to the delay of the individual pump switches. 5) VOUT Comparator and Output Control. A 306mV reference voltage is compared to feedback output voltage to control the VOUT needed for the application. Output current is set by a bias resistor from FB pin to GND pin chosen by the relationship: I = VFB
OUT
THEORY OF OPERATION The SP6682 regulated charge pump block diagram consists of four main blocks (Voltage Reference, Mode Control, Clock Manager, Start-up and Charge-Pump Switches) and two comparators (VMODE Comparator and VOUT Comparator). 1) Voltage Reference. This block provides the 306mV and 1.25V reference voltages needed for the two comparators. 2) Mode Control. An external voltage divider connected to the VMODE pin will define
RFB
where VFB = 306mV.
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
5
APPLICATION INFORMATION
CONFIGURING THE SP6682 AS VOLTAGE OR CURRENT SOURCE The white LED load configuration used by customers can be discrete white LEDs or a white LED module. Inside the white LED module, there may or may not be resistors in series with the white LEDs. According to the different application requirements, the SP6682 can be configured as either a voltage source or a current source to provide solutions for these different applications, as shown in figures 10-13. Figure 10 shows a circuit using the SP6682 to drive discrete white LEDs as a current source. A 3-wire white LED module with internal series resistors as shown in figure 11 can also be driven in this way.
Anode
FB
3-wire W-LED module
GND
Fig 11. 3-wire white LED module
VOUT
1
SP6682
FB
5
Rb
In Figure 12, the SP6682 was used to drive a 2-wire white LED module without internal series resistors as a current source. The bias resistor RB is selected to regulate the total current of the white LED module instead of the current of single LED as in Figure 10.
Rb
GND
8
2.2uF
VOUT
Anode
1
SP6682
2-wire W-LED module
Figure 10. Driving discrete white LEDs as current source
GND
VFB
5
Cathode
Rb
The current in one white LED current is set by the ratio of the feedback pin voltage (306mV) and the bias resistor RB. To set the operating current, RB can be selected by: RB = VFB ILED The current of the remaining white LEDs is set according to the similarity of the white LEDs.
8
Figure 12. Driving 2-wire white LED module as current source
In this application, the bias resistor can be selected by: R = VFB
B
ILED (TOTAL)
where ILED(TOTAL) is the total operating current of all the white LEDs.
(c) 2006 Sipex Corporation
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
6
APPLICATION INFORMATION: Continued To use the SP6682 as a voltage source for fixed voltage applications, a voltage divider is needed to program the ouput voltage, as shown in Figure 13.
VOUT
1
R5
Anode
The guideline for divider resistor selections is as follows: For high input voltage, the SP6682 will work in X1.5 mode. When the input voltage drops to the VTH threshold voltage, it will switch to X2 mode automatically. The VTH threshold voltage for mode change can be calculated by: VTH = (VF + 0.306 + M * ILED * ROUT)/1.5
SP6682
2.2uF
VFB
5
R6
GND
8
2-wire W-LED module
Cathode
Where VF and M are the forward voltage and number of the white LEDs, ROUT is the output resistance of the SP6682. The equation for the voltage divider R1 and R2 with VMODE = 1.25V is: VTH = 1.25V * (1+R1/R2) which can be expressed as R1: R1 = (VTH / 1.25 -1) * R2 For the typical SP6682 application, Using VF=3.6V, M=4, ILED=15mA, ROUT=16, the VTH will be 3.24V. Select R2=100k, then R1=158k. CAPACITOR SELECTION Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. The fly capacitor controls the strength of the charge pump. Selection of the fly capacitor is a trade-off between the output voltage ripple and the output current capability. Decreasing the fly capacitor will reduce the output voltage ripple because less charge will be delivered to the output capacitor. However, smaller fly capacitors lead to larger output resistance, thus decreasing the out-
Figure 13. Driving 2-wire white LED module as voltage source
The output voltage is set by the ratio of the two resistors and the feedback control voltage as shown by: VOUT = ( 1 + R5 ) * VFB R6
PROGRAMMING THE OPERATING MODE SP6682 can automatically change from X1.5 mode to X2 mode for highest efficiency. To use this feature, divider resistors should be chosen according to the specific application, as shown in Figure 14.
VIN
R1
3
VIN
4
R2
C2
SP6682
VMODE
GND
8
Figure 14. Programming the Vmode Resistors
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
7
APPLICATION INFORMATION: Continued
put current capability and the circuit efficiency. Place all the capacitors as close to the SP6682 as possible for layout. Increasing the value of the input and output capacitors could further reduce the input and output ripple. Refer to Table 1 for some suggested low ESR capacitors.
MANUFACTURER PART NUMBER
I1 I2
=
VOUT - VF1 VOUT - VF2
where I1, I2 are the operating current of the white LEDs andVF1,VF2 are the forward voltage of the white LEDs.
CAPACITOR/ SIZE/TYPE ESR AT 100kHz
CAPACITANCE/ VOLTAGE
TDK
C2012X5R1A225K
2.2F/10V
0805/X5R
0.030
TDK
C2012X5R0J475K
4.7F/6.3V
0805/X5R
0.020
MURATA
GRM188R60J225KE01D
2.2F/6.3V
0603/X5R
0.030
MURATA
GRM219R60J475KE01D
4.7F/6.3V
0805/X5R
0.020
Table 1:
Suggested Low ESR Capacitors
BRIGHTNESS CONTROL USING PWM Dimming control can be achieved by applying a PWM control signal to the EN/PWM pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of the PWM signal. While the operating frequency range of the PWM control is from 60Hz to 700Hz, the recommended maximum brightness frequency range of the PWM signal is from 60Hz to 200Hz. A repetition rate of at least 60Hz is required to prevent flicker. BRIGHTNESS MATCHING For white LEDs, the forward voltage drop is a function of the operating current. However, for a given current, the forward voltage drops do not always match due to normal manufacturing tolerances, thus causing uneven brightness of the white LEDs. In Figure 15, assume high-precision bias resistors were used, the operating current ratio of two different branches can be easily derived as shown by:
Since the brightness of the white LED is proportional to the operating current, for better brightness matching, a higher output voltage could be used. This could be done by using a larger resistor, as shown in Figure 15. RB2 is used to bias the operating current of the white LED, RB1 is used to increase the output voltage. Better brightness matching was achieved at the cost of the power wasted on the bias resistor.
VOUT
1
I1
D1
I2
D2
In
Dn
VF1
VF2
VFn
SP6682
5
VFB
Rb1
Rb Rb2
Rb
GND
8
Rb
Figure 15. Increasing brightness matching
Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs (c) 2006 Sipex Corporation
8
APPLICATION INFORMATION: Continued
POWER EFFICIENCY The efficiency of driving the white LEDs can be calculated by:
= VF * I F =
Vi *Ii
VF * IF VF Vi * n Vi * (n * IF + I Q)
Where Vi, Ii are input voltage and current VF, IF are the forward voltage and operating current of White LEDs; IQ is quiescent current, which is considered small compared with IF; n is the boost ratio (X1.5 or X2).
SP6682 HIGH VOLTAGE WHITE LED DRIVER The SP6682 can also be configured as a high voltage boost converter to drive more than 10 white LEDs. Figure 16 shows the schematic of this application as well as actual data showing efficiency of > 85%. By using an external inductor, MOSFET and diode, high output voltages can be generated to drive 12 white LEDs (2 branches -- each branch has 6 white LEDs in series). The current through the white LEDs is determined by: ILED = VFB R1
L1 LQH32CN4R7M11 4.7uH
DS SCHOTTKY MBR0530
ILED = VFB/R1 = 20mA
D1
D2
D7
D8
100 95
Efficiency (%)
SP6682
1
Vin: 2.7-4.2V
2
VOUT C1P VIN VMODE FB
C2P C1N GND C2N EN/PWM
10
9
2.2uF 25V C3 X5R Ceramic
D3
D9
3
4
8
7
90 85 80 75
Q1 SI1304
SOT23 25V
D4
D10
C1
5
R3 1M
6
10uF X5R Ceramic
D5
D6
D11
EN/PWM
D12
R1 15
R2 15
70
2.7
3.0
3.3
3.6
3.9
4.2
VIN (V)
Figure 16. Using SP6682 as a High Voltage White LED Driver
PINOUTS
V
10
OUT C1P V IN
1 2 3 4 5
C2P C1N GND C2N EN/PWM
VOUT 1 C1P 2 VIN 3 VMODE 4 FB 5
10 C2P
SP6682
10 Pin DFN
9 8 7 6
SP6682
10 Pin MSOP
9 C1N 8 GND 7 C2N 6 EN
V
MODE FB
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
9
PACKAGE: 10 PIN MSOP
TOP VIEW
D
D/2
FRONT VIEW
Gauge Plane
o1 R1
e1
R
L2
10 9 8 7 6
E/2
o
L
Seating Plane
o1
c
E
E1
1
2
(L1)
1 2 3 4 5
Seating Plane
e
A A1
A2
Pin #1 designator to be within this INDEX AREA (D/2 * E1/2)
SIDE VIEW
b
10 Pin MSOP SYMBOL
JEDEC MO-187
Variation BA Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm
Dimensions in Millimeters: Controlling Dimension MIN 0.00 0.08 0.07 0.07 0 5 0.75 0.17 NOM 0.85 3.00 BSC 4.90 BSC 3.00 BSC 0.50 BSC 2.00 BSC 0.40 0.60 0.95 REF 0.25 BSC MAX 0.15 0.23 8 15 1.10 0.95 0.33
A1 c R R1 o o1 A A2 b D E E1 e e1 L L1 L2
MIN 0.000 0.004 0.003 0.003 0 5 0.030 0.007
NOM 0.034 0.118 BSC 0.193 BSC 0.118 BSC 0.020 BSC 0.079 BSC 0.024 0.037 REF 0.010 BSC
MAX 0.006 0.009 8 15 0.043 0.038 0.013
0.80
0.016
0.032
SIPEX Pkg Signoff Date/Rev:
Date: 7/19/06 Rev D
JL Aug09-05 RevA
(c) 2006 Sipex Corporation
SP6682 High Efficiency Charge Pump Regulator for White LEDs
10
PACKAGE: 10 PIN DFN
D
D/2
o
E/2
E
A
(A3)
A1
Seating Plane
SIDE VIEW
Pin1 Designator to be within this INDEX AREA (D/2 x E/2)
TOP VIEW
D2
D2/2
1 2 3 4 5
INDEX AREA (D/2 x E/2)
E2/2
E2
L
10 9 8 7 6
K e b
BOTTOM VIEW
3x3 10 Pin DFN SYMBOL
JEDEC MO-229
VARIATION VEED-5 Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 0.032 0.036 0.039 0.000 0.001 0.002 0.008 REF 0.008 0 14 0.008 0.010 0.012 0.119 BSC 0.087 0.106 0.119 BSC 0.056 0.069 0.020 BSC 0.012 0.016 0.020 JL Aug09-05 / RevA
Dimensions in Millimeters: Controlling Dimension MIN 0.80 0.00 MAX 1.00 0.05 14 0.30 2.70 1.75 0.50
A A1 A3 K o
NOM 0.90 0.02 0.20 REF 0.20 0 b 0.18 0.25 D 3.00 BSC D2 2.20 E 3.00 BSC E2 1.40 e 0.50 BSC L 0.30 0.40 SIPEX Pkg Signoff Date/Rev:
Date: 7/19/06 Rev D
SP6682 High Efficiency Charge Pump Regulator for White LEDs
(c) 2006 Sipex Corporation
11
ORDERING INFORMATION
Part Number Top Mark Operating Temperature Range Package Type
SP6682EU ....................... SP6682EU....................................-40C to +85C ............................ 10 Pin MSOP SP6682EU/TR ................. SP6682EU....................................-40C to +85C ............................ 10 Pin MSOP SP6682ER ........................ SP6682ERYWW.........................-40C to +85C ................................ 10 Pin DFN SP6682ER/TR ................. SP6682ERYWW...........................-40C to +85C ............................... 10 Pin DFN
Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6682ER/TR = standard; SP6682ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for MSOP and 3,000 for DFN.
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs (c) 2006 Sipex Corporation
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