UC3842B, 43B UC2842B, 43B

13

MOTOROLA ANALOG IC DEVICE DATA

Figure 28. Bipolar Transistor Drive

Figure 29. Isolated MOSFET Drive

Figure 30. Latched Shutdown

Figure 31. Error Amplifier Compensation

6(10)

5(8)

3(5)

RS

Q1

Vin

C1

Base Charge

Removal

The totem pole output can furnish negative base current for enhanced transistor

turn–off, with the addition of capacitor C1.

S

R

5.0V Ref

Q

7(11)

6(10)

5(8)

3(5)

RS

Q1

VCC

IB

+

–

0

Vin

Isolation

Boundary

VGS Waveforms

+

–

0

+

–

0

50% DC

25% DC

Ipk +

V(Pin1) * 1.4

3RS

NS

Np

Comp/Latch

7(12)

R

C

NS

NP

+

–

+

–

Bias

+

Osc

R

R

R

2R

EA

5(9)

1(1)

2(3)

4(7)

8(14)

The MCR101 SCR must be selected for a holding of < 0.5 mA @ TA(min). The simple two transistor circuit can

be used in place of the SCR as shown. All resistors are 10 k.

MCR

101

2N

3905

2N

3903

+

R

2R

1.0mA

EA

2(3)

5(9)

2.5V

1(1)

Rf

Cf

Rd

Ri

From VO

Error Amp compensation circuit for stabilizing any current mode topology except for boost and flyback

converters operating with continuous inductor current.

Rf ≥ 8.8 k

+

R

2R

1.0mA

EA

2(3)

5(9)

2.5V

1(1)

Rf

Cf

Rd

Rp

From VO

Error Amp compensation circuit for stabilizing current mode boost and flyback

topologies operating with continuous inductor current.

Cp

Ri

1.0 mA