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GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Description
GM384XA series is high performance with fixedfrequency current mode PWM controllers. They are specially designed for off-Line and DC-to-DC converter applications with minimum 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 0.17mA typ. start-up current, allowing an efficient bootstrap supply voltage design. The U.V.L.O. thresholds for the AMC3842A/44A are 16V (on) and 10V (off) which are ideal for off-line applications. The corresponding typical threshold for the GM3843A/45A is 8.4V (on) and 7.6V (off). The GM3842A/43A can operated within 100% duty cycle and the GM3844A/45A can operated within 50% duty cycle.
Features
Low Start-Up and Operating Current Automatic Feed Forward Compensation Current Mode Operating Frequency up to 500KHz Trimmed Oscillator Discharge Current for Precise Duty Cycle Control Latching PWM for Cycle-By-Cycle Current Limiting Under Voltage Lockout with Hysteresis High Current totem Pole Output Stage
Available Options
Device GM3842A GM3843A GM3844A GM3845A Start-UP Voltage 16V 8.4V 16V 8.4V Hysteresis 6V 0.8V 6V 0.8V Max. Duty Cycle < 100% < 100% < 50% < 50%
Application
Off-line flyback or forward converters DC-to DC buck boost converter Monitor Power Supply
www.gammamicro.com.tw 1
GM384x V1.00
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Marking Information and Pin Configurations (Top View)
SO8 DIP8
7.
VCC
6. Output 5. GND
7. VCC 8. VREF 6. Output 5. GND
8. VREF
GM384X AYWW
GM384X AYWW
1. COMP 2. FB
4. 3.
RT / CT ISENSE
1. Output A 2. Input A -
4. RT / CT 3. ISENSE
A: Assembly / Test site code Y: Year WW: Week
Ordering Information
Ordering Number GM3842AD8T GM3842AS8T GM3842AS8R GM3843AD8T GM3843AS8T GM3843AS8R GM3844AD8T GM3844AS8T GM3844AS8R Package DIP-8 SOP-8 SOP-8 DIP-8 SOP-8 SOP-8 DIP-8 SOP-8 SOP-8 DIP-8 SOP-8 SOP-8 Shipping 60 Units / Tube 100 Units / Tube 2,500 Units / Tape & Reel 60 Units / Tube 100 Units / Tube 2,500 Units / Tape & Reel 60 Units / Tube 100 Units / Tube 2,500 Units / Tape & Reel 60 Units / Tube 100 Units / Tube 2,500 Units / Tape & Reel
GM384x V1.00
2
GM3845AD8T GM3845AS8T GM3845AS8R
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Absolute Maximum Ratings
PARAMETER Supply Voltage (low impedance source) Output Current, Source or Sink * Input Voltage (analog inputs pins 2, and 3) Maximum Power Dissipation (TA= 25C) Error Amp Output Sink Current Operating Ambient Temperature Range Storage Temperature Lead Temperature (soldering 10 sec.)
* Maximum Package Power Dissipation Limits must be observed.
Symbol VCC IO VI PD ISINK(E.A.) TA
RATINGS 30 1 - 0.3 to + 5.5 1.0 10 - 40 to 125- 65 to 150 260
UNITS V A V W mA J J J
Block Diagram
7
Internal Bias
VCC
U.V.L.O. 5V VREF EN
36V
VREF
8
5
GND
VREF Good Logic Error Amp Current Sense 1V R PWM Latch
7V CC
2R R
VFB
COMP
2 1
6
S
OUTPUT
CURRENT SENSE
3
T Oscillator
5
RT/CT
4
GND
3
GM384x V1.00
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Electrical Characteristics (TA = 0C to 70C, *VCC=15V, CT=3.3nF, RT=10k , unless otherwise
specified) Parameter Reference Section
Reference output Voltage Line Regulation Load Regulation Short CirCuit output Current VREF VREF-V VREF-I ISC TJ= 25C, IREF= 1mA 12V < VCC < 25V 1mA < IREF < 20mA TA=25C 4.9 5.0 6.0 6.0 -100 5.1 20 25 -180 V mV mV mA
Symbol
Condition
Min
Typ
Max
Unit
Oscillator Section
Oscillation Frequency Frequency Change with Voltage @ Oscillator Amplitude f TJ= 25C 47 52 0.05 1.6 57 1 KHz % V
f/VCC 12V < VCC < 25V V(osc) (Peak to Peak)
Error Amplifier Section
Input Bias Current Input Voltage Open Loop Voltage Gain Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage IBIAS VI(EA) AVOL(EA) VFB = 3V VPIN1 = 2.5V 2V < VO < 4V 2.42 65 60 2 -0.5 5.0 -0.1 2.5 90 70 7 -1.0 6.0 0.8 1.1 -2 2.58 A V dB dB mA mA V V
PSRR(EA) 12V < VCC < 25V ISINK(EA) Isource(EA) VOH(EA) VOL(A) VPIN2 = 2.7V, VPIN1 = 1.1V VPIN2 = 2.3V, VPIN1 = 5V VPIN2 = 2.3V, RL =15K to GND VPIN2 = 2.7V, RL =15K to GND
Current Sense Section
Current Sense Input Voltage Gain Maximum Input Signal Supply Voltage Rejection Input Bias Current GV VI(MAX) SVR IBIAS (Note 1 and 2) VPIN1 = 5V (Note 1) 12V < VCC < 25V (Note 1) VPIN3 = 3V 2.85 3.0 1.0 70 -3.0 -10 3.15 1.1 V/V V dB A
Output Section
GM384x V1.00
Low Output Voltage
VOL
ISINK = 20mA ISINK = 200mA
0.8 1.4 13 12 13.5
0.4 V 2.2 V
High Output Voltage Rise Time Fall Time
VOH tr tf
ISource= -20mA Isource = -200mA TJ = 25C, CL = 1nF (Note 3) TJ = 25C, CL = 1nF (Note 3)
13 45 35 150 150 ns ns
4
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Electrical Characteristics (TA = 0C to 70C, VCC=15V, CT=3.3nF, RT=10k , unless otherwise
specified) Parameter Symbol Condition Min Typ Max Unit
Undervoltage Lockout Section
GM3842A, GM3844A Start Threshold Minimum Operating Voltage (after turn on) VTH(ST) GM3843A, GM3845A GM3842A, GM3844A VOPR(MIN) GM3843A, GM3845A 7.0 7.6 8.2 7.8 8.5 8.4 10 9.0 11.5 V 14.5 16.0 17.5 V
PWM Section
GM3842A, GM3844A Maximum Duty Cycle Minimum Duty Cycle D(MAX) GM3843A, GM3845A D(MIN) 47 45 50 0 % 95 97 100 %
Total Standby Current
Start-Up Current Operating Supply Current Zero Voltage IST ICC(OPR) VZ VPIN3 = VPIN2 = 0V ICC = 25mA 30 0.17 13 35 0.3 17 mA mA V
* Adjust VCC above the Startup threshold before setting to l5 V. Note 1: Parameter measured at trip point of latch with VPIN2 = 0V Note 2: Gain defined as A = VPIN1 / VPIN3; 0V< VPIN3 < 0.5V Note 3: These parameters, although quaranteed, are not 1005 tested in production
5
GM384x V1.00
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Typical Performance Characteristics
RT (K) 50
CT = 1nF CT = 1000pF CT = 200pF CT = 500pF
%
VCC = 15V
50 30 20 10
CT = 5nF CT = 10pF CT = 2nF CT = 1nF CT = 500pF CT = 200pF CT = 1000pF
20 10
CT = 2nF
5
CT = 5nF CT = 10pF
5
2 VCC = 15V 1 TA = 25C 10 20 50 100 200 300 500 fosc (KHZ)
2 1 10 20 30 50 100 200 300 500 fosc (kHz)
Figure 1. Timing Resistor vs. Oscillator Frequency Dmax (%) VCC = 15V 90 CT = 3.3nF TA = 25C 80 70 60 50 40 RT (k Figure 3. Maximum Output Duty Cycle vs. Timing Resistor (GM3842A/43A)
1 2 3 5
Figure 2. Output Dead-Time vs. Oscillator Frequency (dB) 80 60 40 20 0 -20 l0
VCC = 15V VO = 2V to 4V RL = 100K TA = 25C
l00
lk
l0k
l00k
lM
Figure 4. Error Amp Open-Loop Gain vs. Frequency ISC (mA)
VTH (V) VCC = 15V 1.0 0.8 0.6 0.4 0.2 TA = 125C TA = 25C
l00
90
VCC = 15V 80 70 60 50
0
2
4
6
VO (V)
Figure 5. Current Sense Input Threshold vs. Error Amp Output Voltage Vsat (V) -1 -2
50g s Pulsed Load 120Hz Rate Source Saturation (Load to Ground)
0 25 50 75 l00 T (C) A Figure 6. Reference Short Circuit Current vs. Temperature
GM384x V1.00
ICC (mA)
VCC = 15V
20 l5 10
Sink Saturation (Load to V+)
ISENSE = 0V VFB = 0V RT = 10K TA = 25C CT = 3.3nF
3 2 l 0
0 200 400 600 Io (mA)
5 0 0
GM3843A / 45A
GM3842A / 44A
10
20
30
VCC (V)
6
Figure 7. Output Saturation Voltage vs. Load Current TA= 25C
Figure 8. Supply Current vs. Supply Voltage
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Package Outline Dimensions - SO 8
0.189 - 0.197 (4.800 - 5.004)
0.228 - 0.244 (5.791 - 6.198) 0.016 - 0.050 (0.406 - 0.270)
D
0.014 - 0.020 (0.356 - 0.508)
0.050 (1.270) TYP
0.150 - 0.157 (3.810 - 3.988)
0.053 - 0.059 (1.346 - 1.753)
SEATING PLAN
0.004 - 0.010 (0.012 - 0.254)
0.008 - 0.010 (0.203 - 0.254)
8.0 MAX
Package Outline Dimensions - DIP 8
0.250 +/- 0.005 (6.350 +/- 0.127)
0.370 - 0.400 (9.474 - 10.150)
0.06 (1.524) 0.145 - 0.200 (3.683 - 5.080)
0.300 - 0.320 (7.620 - 8.128)
0.125 - 0.140 (3.175 - 3.556) 0.045 +/- 0.015 (1.143 +/- 0.183) 0.100 +/- 0.010 (2.540 +/- 0.254) 0.108 +/- 0.003 (0.457 +/- 0.076)
J
95 +/- 5
7
GM384x V1.00
0.009 - 0.010 (0.299 - 0.381)
GM3842A, GM3843A GM3844A, GM3845A
CURRENT MODE PWM CONTROLLER
Ordering Number
GM 3842 A
APM Gamma Micro Circuit Type Revision
S8
Package Type S8: SO 8 D8: DIP 8
R
Shipping Type R: Taping & Reel T: Tube
GM384x V1.00
8
1

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