UC3842B(2013) Просмотр технического описания (PDF) - ON Semiconductor

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Компоненты Описание

производитель

UC3842B
(Rev.:2013)

High Performance Current Mode Controllers

ON Semiconductor 

UC3842B, UC3843B, UC2842B, UC2843B

VCC

Vin

7(12)

5.0V Ref

+

-

S

Q

R

Comp/Latch

+

-

7(11)

Rg

Q1

6(10)

5(8)

3(5)

RS

Series gate resistor Rg will damp any high frequency parasitic oscillations

caused by the MOSFET input capacitance and any series wiring inductance in

the gate-source circuit.

Figure 29. MOSFET Parasitic Oscillations

IB

+

0

-

Vin

Base Charge

Removal

C1

Q1

6(10)

5(8)

3(5)

RS

The totem pole output can furnish negative base current for enhanced

transistor turn-off, with the addition of capacitor C1.

Figure 30. Bipolar Transistor Drive

5.0V Ref

+

-

S

Q

R

Comp/Latch

VCC

Vin

7(12)

Isolation

Boundary

+

-

7(11)

6(10)

5(8)

3(5)

C

VGS Waveforms

+

Q1

+

0

0

-

-

50% DC

25% DC

ǒ Ǔ Ipk

+

V(Pin1) *

3 RS

1.4

 

NS

Np

R

RS NS

NP

Figure 31. Isolated MOSFET Drive

8(14)

R

Bias

R

Osc

4(7)

+

1.0 mA 2R

2(3)

EA

R

1(1)

MCR

2N

101

3905

5(9)

2N

3903

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.

Figure 32. Latched Shutdown

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