CM3842 データシートの表示（PDF） - Unspecified

部品番号

コンポーネント説明

メーカー

CM3842

CURRENT MODE PWM CONTROLLER

Unspecified 

APPLICATION INFORMATION

CM3842/3843

CURRENT MODE PWM CONTROLLER

Error

Amp

Rf

RS

COMP

ISENSE

Cf GND

2R

R

1V

Current

Sense

Comparator

Fig. 1. Current Sense Circuit

Peak current (IS) is set by: IS(MAX) = 1V/RS

2.5V

Error

Amp

0.5mA

Zi

VFB

Zf COMP

VREF

RT

RT/CT

CT

GND

Fig. 2. Error Amplifier Configuration - the

amplifier can source or sink up to 0.5mA

Fig. 3. Oscillator Section

1.72

For RT < 5K, f = RTCT

VREF

RT

4.7K

1K

Error AMP

Adjust

4.7K

2N2222

100K

5K

ISENSE

Adjust

COMP VREF

VFB

VCC

ISENSE Output

RT/CT GND

CT

0.1µF

1K,

1W

0.1µF

VCC

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 ISENSE pin

2001/06/27 Advanced

Champion Microelectronic Corporation

Page 6

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