UC3842B, UC3843B, UC2842B, UC2843B, NCV3843BV
80
50
R T, TIMING RESISTOR (k
Ω
)
20
8.0
5.0
2.0
0.8
10 k
V
CC
= 15 V
T
A
= 25°C
20 k
50 k
100 k
200 k
500 k
f
OSC
, OSCILLATOR FREQUENCY (kHz)
1.0 M
% DT, PERCENT OUTPUT DEADTIME
100
1. C
T
= 10 nF
50 2. C
T
= 5.0 nF
3. C
T
= 2.0 nF
4. C
T
= 1.0 nF
20 5. C
T
= 500 pF
6. C
T
= 200 pF
10 7. C
T
= 100 pF
5.0
2.0
1.0
10 k
20 k
4
3
2
1
5
6
7
V
CC
= 15 V
T
A
= 25°C
50 k
100 k
200 k
500 k
f
OSC
, OSCILLATOR FREQUENCY (kHz)
1.0 M
Freq
+
Ct
Vosc
IRt
1
Vosc
)
Ct
Idis*IRt
Where: Vosc = 1.7 V
I
Rt
= Vref/Rt
Idis = 8.3 mA
Figure 2. Timing Resistor
versus Oscillator Frequency
Figure 3. Output Deadtime
versus Oscillator Frequency
9.0
I dischg , DISCHARGE CURRENT (mA)
V
CC
= 15 V
V
OSC
= 2.0 V
8.5
D max , MAXIMUM OUTPUT DUTY CYCLE (%)
100
90
80
70
60
50
40
0.8
I
dischg
= 8.8 mA
V
CC
= 15 V
C
T
= 3.3 nF
T
A
= 25°C
5.0 6.0 7.0 8.0
I
dischg
= 7.5 mA
8.0
7.5
7.0
− 55
− 25
0
25
50
75
T
A
, AMBIENT TEMPERATURE (°C)
100
125
1.0
2.0
3.0
4.0
R
T
, TIMING RESISTOR (kW)
Figure 4. Oscillator Discharge Current
versus Temperature
Figure 5. Maximum Output Duty Cycle
versus Timing Resistor
2.55 V
V
CC
= 15 V
A
V
= −1.0
T
A
= 25°C
20 mV/DIV
3.0 V
V
CC
= 15 V
A
V
= −1.0
T
A
= 25°C
20 mV/DIV
1.0
ms/DIV
2.50 V
2.5 V
2.45 V
0.5
ms/DIV
2.0 V
Figure 6. Error Amp Small Signal
Transient Response
Figure 7. Error Amp Large Signal
Transient Response
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