UC3842A, 43A UC2842A, 43A
Figure 32. Slope Compensation
V
CC
V
in
7(12)
8(14)
+
5.0V
ref
–
+
–
R
R
R
T
Bias
+
–
MPS3904
+
7(11)
6(10)
5(8)
–
4(7)
R
Slope
Osc
From V
O
C
T
+
–m
1.0mA
S
R
R
i
2(3)
+
–
Q
–
+
2R
R
EA
Comp/Latch
C
1.0V
R
f
R
f
d
m
3(5)
R
1(1)
S
–3.0 m
5(9)
The buffered oscillator ramp can be resistively summed with either the voltage feedback or current sense inputs to provide slope compensation.
Figure 33. 27 Watt Off–Line Flyback Regulator
L1
MBR1635
2200
+
4.7Ω
3300pF
MDA
202
4.7k
250
5.0V/4.0A
T1
+
+
+
+
1000
56k
115Vac
5.0V RTN
12V/0.3A
MUR110
1000
1N4935
68
1N4935
L2
10
7(12)
+
+
±
12V RTN
47
100
1000
10
L3
8(14)
+
–
+
+
5.0V
ref
–12V/0.3A
+
0.01
MUR110
680pF
1N4937
Bias
+
–
+
10k
7(11)
1N4937
2.7k
4(7)
2(3)
22
Ω
Osc
6(10)
4700pF
+
MTP
4N50
18k
S
+
–
Q
–
+
L1 – 15
L2, L3 – 25
µ
H at 5.0 A, Coilcraft Z7156.
5(8)
3(5)
R
µH at 1.0 A, Coilcraft Z7157.
EA
Comp/Latch
4.7k
1.0k
470pF
T1 – Primary: 45 Turns # 26 AWG
T1 – Secondary 12 V: 9 Turns # 30 AWG
T1 – (2 strands) Bifiliar Wound
T1 – Secondary 5.0 V: 4 Turns (six strands)
T1 – #26 Hexfiliar Wound
1(1)
0.5Ω
±
5(9)
T1 – Secondary Feedback: 10 Turns #30 AWG
T1 – (2 strands) Bifiliar Wound
T1 – Core: Ferroxcube EC35–3C8
T1 – Bobbin: Ferroxcube EC35PCB1
Test
Conditions
= 95 Vac to 130 Vac
Results
T1 – Gap
≈
0.01” for a primary inductance of 1.0 mH
Line Regulation: 5.0 V
V
in
∆ = 50 mV or ± 0.5%
∆ = 24 mV or ± 0.1%
± 12 V
Load Regulation: 5.0 V
V
in
V
in
= 115 Vac, I
= 115 Vac, I
= 1.0 A to 4.0 A
= 100 mA to 300 mA ∆ = 60 mV or ± 0.25%
∆ = 300 mV or ± 3.0%
out
out
± 12 V
Output Ripple:
5.0 V
± 12 V
V
in
= 115 Vac
40 mV
80 mV
pp
pp
Efficiency
V
in
= 115 Vac
70%
All outputs are at nominal load currents, unless otherwise noted.
13
MOTOROLA ANALOG IC DEVICE DATA
ONSEMI [ ONSEMI ]
