UC3842AD ON Semiconductor, UC3842AD Datasheet - Page 13

• Manufacturer Part Number: UC3842AD
• Description: Other Power Management 52kHz 1A Current PWM
• Manufacturer: ON Semiconductor
• Type: High Performance Current Mode Controllersr

Specifications of UC3842AD

• Output Voltage Range: 4.9 V to 5.1 V
• Input Voltage Range: 30 V
• Operating Temperature Range: 0 C to + 70 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-14
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Figure 27. Current Waveform Spike Suppression
The totem−pole output can furnish negative base current for enhanced
transistor turn−off, with the addition of capacitor C
The addition of the RC filter will eliminate instability caused by the leading
edge spike on the current waveform.
The MCR101 SCR must be selected for a holding of less than 0.5 mA at T
The simple two transistor circuit can be used in place of the SCR as shown. All
resistors are 10 k.
Figure 29. Bipolar Transistor Drive
MCR
101
−
+
5.0V
+
0
−
−
+
+
−
ref
I
B
Comp/Latch
Figure 31. Latched Shutdown
3905
S
R
2N
Q
6(1)
5(8)
3(5)
+
−
Removal
+
Charge
7(12)
−
Base
3903
2N
8(14)
4(7)
2(3)
1(1)
C
1
V
CC
7(11)
6(10)
5(8)
3(5)
1
UC3842A, UC3843A, UC2842A, UC2843A
.
+
−
Q1
R
EA
V
R
R
S
in
C
+
R
Osc
1.0mA
Bias
Q1
R
V
2R
S
in
R
A(min)
5(9)
.
http://onsemi.com
−
+
5.0V
13
−
+
+
−
ref
Comp/Latch
S
R
Q
Error Amp compensation circuit for stabilizing current−mode boost and flyback
topologies operating with continuous inductor current.
Error Amp compensation circuit for stabilizing any current−mode topology except
for boost and flyback converters operating with continuous inductor current.
Series gate resistor R
caused by the MOSFET input capacitance and any series wiring inductance
in the gate−source circuit.
+
−
Figure 30. Isolated MOSFET Drive
C
Figure 28. MOSFET Parasitic Oscillations
Figure 32. Error Amplifier Compensation
R
p
From V
+
7(12)
−
R
p
From V
R
d
i
−
+
R
O
C
5.0V
R
O
i
I
V
d
7(11)
6(1)
5(8)
3(5)
−
+
CC
+
−
ref
C
Comp/Latch
g
C
I
R
will damp any high frequency parasitic oscillations
S
R
2(3)
1(1)
f
Q
Boundary
Isolation
R
R
R
S
2(3)
1(1)
+
f
−
2.5V
+
−
+
7(12)
−
N
EA
2.5V
S
+
+
−
Q1
1.0mA
EA
V
CC
7(11)
6(10)
5(8)
3(5)
+
N
V
+
0
2R
p
−
I
pk
in
É É É
1.0mA
R
50% DC
=
R
2R
g
É
V
V
5(9)
(pin 1)
R
GS
3 R
Waveforms
− 1.4
5(9)
S
Q1
+
0
R
−
V
S
in
É É É É
25% DC
N
N
P
S