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AMC DOC. #: AMC3842B_C (LF) March 2004 (R)
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
FEATURES
ADD MICROTECH CORP.
DESCRIPTION
The AMC3842B/43B are fixed frequency current-mode PWM controllers specially designed for OFF-Line switching power supply and DC-to-DC converters with a minimum number of external components. These devices feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator, and high current totem pole output which is suitable for driving MOSFETs. The under voltage lock-out (U.V.L.O.) is designed to operated with 200A typ. start-up current, allowing an efficient bootstrap supply voltage design. The U.V.L.O. thresholds for the AMC3842B are 16V (on) and 10V (off) which are ideal for off-line applications. The corresponding typical threshold for the AMC3843B are 8.4V (on) and 7.6V (off). The AMC3842B/43B can operated within 100% duty cycle.
APPLICATIONS
Low Start-Up current ( typ. 200A) Optimized for Off-Line and DC-to-DC Converters Maximum Duty Cycle U.V.L.O. with Hysteresis Operating Frequency Up to 500KHz Internal Trimmed Bandgap Reference High Current Totem Pole Output Error Amplifier With Low Output Resistance Available in 8-Pin Plastic DIP and Surface Mount 14-Pin S.O.I.C. Identical pin assignment to earlier UC384X series.
PACKAGE PIN OUT
COMP VFB ISENSE RT/CT VREF VCC OUTPUT GND
Off-line flyback or forward converters. DC-to-DC buck or boost converter. Monitor Power Supply
AVAILABLE OPTIONS
Device AMC3842B AMC3843B Start-UP Max. Duty Hysteresis Voltage Cycle 16V 8.4V 6V 0.8V < 100% < 100%
COMP NC VFB NC ISENSE NC RT/CT
8-Pin Plastic DIP (Top View)
VREF NC VCC VC OUTPUT GND PWR RT/CT COMP VFB ISENSE VREF VCC OUTPUT GND
14-Pin Plastic S.O.I.C. Surface Mount (Top View)
8-Pin Plastic S.O.I.C. Surface Mount (Top View)
ORDER INFORMATION Plastic DIP-8 Plastic SO-14 Plastic SO-8 M D DM TA (OC) 8-pin 14-pin 8-pin 0 to 70 AMC384XBM AMC384XBD AMC384XBDM 0 to 70 AMC384XBMF(Lead Free) AMC384XBDF(Lead Free) AMC384XBDMF(Lead Free) Note: 1.All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number (i.e. AMC384XBDT, or AMC384XBDMT). 2.The letter "F" is marked for Lead Free process.
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
(Note 1)
ABSOLUTE MAXIMUM RATINGS
35V Supply voltage, VCC Output current, IO 1A -0.3V to 6.3V Analog inputs, VI 10mA Error amp output sink current, ISINK(EA) 1W Power dissipation (TA = 25 OC), PD 150 OC Maximum juncture temperature, TJ Storage temperature range -65OC to 150OC Lead temperature (soldiering, 10 seconds) 260 OC Note 1: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal. THERMAL DATA M PACKAGE: Thermal Resistance-Junction to Ambient, JA D PACKAGE: Thermal Resistance-Junction to Ambient, JA DM PACKAGE: Thermal Resistance-Junction to Ambient, JA Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow.
95 OC/W 120 OC/W 165 OC/W
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
BLOCK DIAGRAM 7 (12)
VCC
Internal Bias
U.V.L.O. 5V EN VREF
36V
VREF
8 (14)
5 (9) GND
VREF Good Logic
7 (11) PWR
Error Amp 2R R 1V Current Sense R PWM Latch
VC
VFB
2 (3)
OUTPUT
COMP 1 (1)
S
6 (10) 3 (5)
T Oscillator
CURRENT SENSE RT/CT 4 (7)
PWR
5 (8) GND
( ) are 14 Pin S.O.I.C. pin number
Note 2 Note 3 Note 4 Note 5
:VCC and PWR VC are internally connected for 8 pin packages. :PWR GND and GND are internally connected for 8 pin packages. :U.V.L.O. is 16V for 3842B and 8.4V for 3843B. :Hysteresis is 6V for 3842B and 0.8V for 3843B.
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
Supply Voltage Input Voltage
RECOMMENDED OPERATING CONDITIONS Recommended Operating Conditions Parameter Symbol Min. Typ. Max. VCC / VC 30 VI,RT/CT VI,ISENSE/VFB VO, Output ICC IO IO(REF) CT fOSC TA 0 0 5.5 30 25 200 -20 100 0 500 70
Units V V V mA mA mA nF KHz O C
Output Voltage Supply Current Average Output Current Reference Output Current Timing Capacitor Oscillator Frequency Operating Free-air Temperature
1
ELECTRICAL CHARACTERISTICS Unless otherwise specified, these specifications apply over the operating ambient temperature for AMC384XB with 0OC TA 70 OC; VCC = 15V(note 6); RT = 10K;CT = 3.3nF. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature. AMC384XB Parameter Symbol Test Conditions Units Min. Typ. Max. Reference Section Reference output Voltage VREF Line Regulation Load Regulation Short Ciruit Output Current ISC Oscillator Section Oscillation Frequency f Frequency Change with Voltage Frequency Change with Temperature (note 7) Peak-to-peak Amplitude At RT/CT VOSC Current Sense Section Gain (note 8 & 9) AVOL Maximum Input Signal (note 8) VI(MAX) Power Supply Rejection Ratio (note 8) PSRR Input Bias Current IBIAS TJ = 25 OC, IREF = 1mA 12V VCC 25V,TJ = 25 OC 1mA IREF 20mA TJ = 25 OC TJ = 25 OC 12V VCC 25V TMIN TA TMAX 4.9 5.0 6 6 -100 52 0.2 5 1.7 2.85 0.9 3.00 1.0 70 -3.0 3.15 1.1 -10 5.1 20 25 -180 V mV mV mA KHz % % V V/V V dB A
-30
1.0
COMP = 5V 12V VCC 25V (note 8)
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
ELECTRICAL CHARACTERISTICS (Continued) Error Amplifier Section Input Bias Current Input Voltage Open Loop Voltage Gain Unity Gain Bandwidth (note 7) Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage Output Section Output Low Level Output High Level Rise Time (note 7) Fall Time (note 7) Under-Voltage Lockout Section Start Threshold Min. Operating Voltage
PWM Section
IBIAS VI(EA) GVO UGBW PSRR ISINK ISOURCE VOH VOL
COMP = 2.5V 2.42 65 2V VO 4V O TJ = 25 C 0.7 60 12V VCC 25V VFB = 2.7V, COMP = 1.1V 2 VFB = 2.3V, COMP = 5.0V -0.5 VFB = 2.3V, RL = 15K to GND 5 VFB = 2.7V, RL = 15K to VREF ISINK = 20mA ISINK = 200mA ISOURCE = 20mA ISOURCE = 200mA TJ = 25 OC, CL = 1nF TJ = 25 OC, CL = 1nF AMC3842B AMC3843B AMC3842B AMC3843B AMC3842B/43B AMC3842B AMC3843B VFB = ISENSE = 0V ICC = 25mA
-0.1 2.50 90 1 70 7 -1.0 6 0.7 0.1 1.4 13.5 13.0 50 50 16.0 8.4 10 7.6 97 0.2 0.5 14 35
-2 2.58
1.1 0.4 2.2
A V dB MHz dB mA mA V V
VOL VOH tr tf
V V
13 12
150 150 17.5 9.0 11.5 8.2 100 0.35 1.0 17
ns ns
VTH(ST)
14.5 7.8 8.5 7.0 94
V V
Maximum Duty Cycle Total Standby Current Startup Current Operating Supply Current Zener Voltage note 6: note 7: note 8: note 9: ICC VZ
%
mA mA V
30
Adjust VCC above the start threshold before setting at 15V These parameters, although guaranteed, are not 100% tested in production prior to shipment Parameters are measured at trip point of latch with VFB = 2V Gain is measured between ISENSE and COMP with the input changing from 0V to 0.8V
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
Application Information
Error Amp
2R R 1V Current Sense Comparator
COMP Rf RS Cf ISENSE GND
Fig. 1. Current Sense Circuit
Peak current (IS) is set by: IS(MAX) = 1V/RS
VREF 2.5V Error Amp Zi VFB 0.5mA RT/CT CT Zf COMP GND RT
Fig. 2. Error Amplifier Configuration - the
amplifier can source or sink up to 0.5mA
Fig. 3. Oscillator Section
For RT < 5K, f = 1.72 RTCT
VREF
RT 2N2222 100K
COMP VREF VCC
VCC
4.7K
1K Error AMP Adjust 4.7K
0.1F 1K, 1W Output 0.1F GND
VFB
5K ISENSE Adjust
ISENSE Output RT/CT GND
CT
Fig. 4. Open-loop laboratory test fixture: Careful grounding techniques are necessary for high peak
currents associated with capacitive loads. Timing and bypass capacitors should be connected to GND pin in a single point ground. The transistor and 5K potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to the ISENSE pin
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
Application Information (continued)
1K
VREF
COMP
Shutdown 330 ISENSE Shutdown 500 To Current Sense Resistor
Fig. 5. Shutdown Techniques - there are two ways to shutdown the PWM controller: 1) raise the voltage at ISENSE above 1V or, 2) pull the COMP below a voltage two diodes above ground.
VREF 0.1F RT
RT/CT CT R2 ISENSE C R1 RSENSE ISENSE
Fig 6. Slop Compensation - To achieve duty cycles over 50% for some applications , the above slope compensation technique is suggested by resistively summing a fraction of the oscillator ramp with the current sense signal.
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
8-Pin Plastic DIP
5
B
8
INCHES MIN TYP MAX
MILLIMETERS MIN 9.02 6.10 1.27 0.20 2.92 TYP 9.27 6.35 0.46 1.52 2.54 3.30 7.62 BSC. 15 7 15 MAX 10.16 7.11 5.33 2.29 0.38 3.81
1
4
A
A
0.355 0.365 0.400 0.240 0.250 0.280 0.018 0.060 0.100 0.210 0.090 0.015
B C
F
L
D F G
C
K H G D
J
H 0.050
M
J K L M
0.008
0.115 0.130 0.150 0.300 BSC. 7
8-Pin Plastic S.O.I.C.
INCHES
MILLIMETERS MAX 0.202 0.163 0.074 0.020 0.035 MIN 4.65 3.66 1.73 0.25 0.38 TYP 1.27 BSC 0.19 0.13 4.80 5.79 0.25 0.25 5.21 8 6.20 MAX 5.13 4.14 1.88 0.51 0.89
A
A B
MIN 0.183 0.144
TYP -
B F
P
C 0.068 D 0.010
D
G L C
F G J
0.015
0.050 BSC 0.007 0.005 0.189 0.228 0.010 0.010 0.205 8 0.244
SEATING PLAN
K
M J
K L M P
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
14-Pin Plastic S.O.I.C.
INCHES MIN
A
MILLIMETERS MAX 0.344 0.158 0.069 0.018 0.030 MIN 8.54 3.81 1.35 0.35 0.67 TYP 1.27 BSC 0.19 0.10 4.82 5.79 0.25 0.25 5.21 8 6.20 MAX 8.74 4.01 1.75 0.46 0.77
TYP -
A B
B F P
0.336 0.159
C 0.053 D 0.014
G
D L C M J
F G J K L M P
0.026
0.050 BSC 0.007 0.004 0.189 0.228 0.010 0.010 0.205 8 0.244
SEATING PLAN
K
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AMC DOC. #: AMC3842B_C (LF) March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
IMPORTANT NOTICE
ADD Microtech (ADDM) reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe property or environmental damage. ADDM integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of ADDM products in such applications is understood to be fully at the risk of the customer. In order to minimize risks associated with the customer's applications, the customer should provide adequate design and operating safeguards. ADDM assumes to no liability to customer product design or application support. ADDM warrants the performance of its products to the specifications applicable at the time of sale.
U.S.
ADD Microtech Inc. 492 Altamont Drive Milpitas, CA 95035 T E L : (408) 9410420 F A X : (408) 9410864
Asia Pacific region
ADD Microtech Corp 13F, NO. 287, Sec. 3, Nan Jing E. Rd., Taipei, Taiwan 105 T E L : 2-27132800 F A X : 2-27132805
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