UC2842ADR2 查看數據表（PDF） - ON Semiconductor
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UC2842ADR2 Datasheet PDF : 18 Pages
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UC3842A, UC3843A, UC2842A, UC2843A
VCC
7(12)
Vin
5.0Vref
+ +−
−
+
−+
−
S
−
+
RQ
Comp/Latch
7(11)
Q1
6(10)
5(8)
R
3(5)
C
RS
The addition of the RC filter will eliminate instability caused by the leading
edge spike on the current waveform.
Figure 27. Current Waveform Spike Suppression
VCC
7(12)
Vin
5.0Vref
+
+−
−
+− +
−
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 28. MOSFET Parasitic Oscillations
IB
Vin
+
0
Base
−
Charge
Removal
C1
Q1
6(1)
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 29. Bipolar Transistor Drive
VCC
Vin
7(12)
5.0Vref
+ +−
−
+− +
−
S
−+ RQ
Comp/Latch
Isolation
Boundary
7(11)
6(1)
5(8)
R
Q1
VGS Waveforms
+
ÉÉ É 0
−
É ÉÉ 50%DC
+
0
−
25% DC
É Ipk =
V(pin 1) − 1.4
3 RS
NP
NS
3(5) C
RS
NS
Np
Figure 30. Isolated MOSFET Drive
MCR
2N
101
3905
8(14)
4(7)
2(3)
1(1)
2N
3903
R
Bias
R
Osc
+
+−
EA
1.0mA
2R
R
5(9)
The MCR101 SCR must be selected for a holding of less than 0.5 mA at TA(min).
The simple two transistor circuit can be used in place of the SCR as shown. All
resistors are 10 k.
Figure 31. Latched Shutdown
From VO
Ri
Rd CI
2.5V +
2(3)
+
1.0mA
−
Rf
EA
2R
R
1(1)
5(9)
Error Amp compensation circuit for stabilizing any current−mode topology except
for boost and flyback converters operating with continuous inductor current.
From VO
Rp Ri
Cp
Rd CI
2.5V +
2(3)
+
1.0mA
Rf
−
EA
2R
R
1(1)
5(9)
Error Amp compensation circuit for stabilizing current−mode boost and flyback
topologies operating with continuous inductor current.
Figure 32. Error Amplifier Compensation
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