LM3842A 查看數據表（PDF） - HTC Korea
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LM3842A Datasheet PDF : 6 Pages
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CURRENT MODE PWM CONTROLLER
LM3842A/3A/4A/5A
Note:
1. Adjust Vcc above the start threshould before setting at 15V.
2. Parameter measured at trip point of latch with VFB - 0.
3. Comparator Gain defined as:
A
=
ΔV Output Compensation(pin FB)
ΔV Current Sanseinput(pin CS)
;
Fig.1 Open Loop Test Circuit
4.7K
RT
2N
2222
1K
E/A
ADJUST
ISENSE
5K
ADJUST
4.7K
100K
1 COMP
VREF 8
2 VFB
VC 7
LM3842A
3 ISENSE
OUTPUT 6
4 RT/CT
CT
GND 5
A
0.1
0.1
VREF
V1
1K/1W
OUTPUT
High peak currents associated with capacitive loads necessitate careful grounding techniques
Timing and bypass capacitors should be connected close to pin 5 in a single point ground.
The transistor and 5KΩ potentiometer are used to sample the oscillator waveform and apply an
adjustable ramp to pin 3.
Fig.2 Under Voltage Lockout
ON/OFF COMMAND
7
TO REST OF IC
ICC
LM3842A
VON
16V
LM3843/5A
8.4V
< 15mA
VOFF
10V
7.6V
< 1mA
VOFF VON
VCC
During Under-Voltage Lock-Out, the output driver is biased to a high impedance state.
Pin 6 should be shunted to ground with a bleeder resistor to prevent activating the power switch
with output leakage current.
−3−
HTC
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