AMC3842B Datasheet, PDF (6/10 Pages) List of Unclassifed Manufacturers – CURRENT MODE PWM CONTROLLER

AMC DOC. #: AMC3842B_C (LF)
March 2004
AMC3842B/43B
CURRENT MODE PWM CONTROLLER
Application Information
Error
Amp
R_f
R_S
COMP
I_SENSE
C_{f GND}
2R
R
1V
Current
Sense
Comparator
Fig. 1. Current Sense Circuit
Peak current (I_S) is set by: I_S(MAX) = 1V/R_S
2.5V
Error
Amp
0.5mA
Z_i
V_FB
Z_f ^COMP
V_REF
R_T
R_T/C_T
C_T
GND
Fig. 2. Error Amplifier Configuration - the
amplifier can source or sink up to 0.5mA
Fig. 3. Oscillator Section
1.72
For R_T < 5K, f = _RTCT
V_REF
R_T
4.7K
1K
Error AMP
Adjust
4.7K
2N2222
100K
5K
I_SENSE
Adjust
COMP ^VREF
V_FB
V_CC
I_{SENSE Output}
R_T/C_T GND
C_T
0.1µF
1K,
1W
0.1µF
V_CC
Output
GND
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 I_SENSE pin
Copyright © 2002, ADD Microtech Corp.
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