UC3844, UC3845, UC2844, UC2845
10
0
75
V
T
= 15 V
= 25°C
CC
A
1.0 nF
50
70
65
60
55
50
2.0 nF
20
5.0 nF
C
T
= 10 nF
10
5.0
2.0
100
pF
NOTE: Output switches
at one−half the oscillator
frequency.
200
pF
500
pF
1.0
10 k
20 k
50 k
100 k
200 k
500 k
1.0 M
10 k
20 k
50 k
100 k
200 k
500 k
1.0 M
f
, OSCILLATOR FREQUENCY (Hz)
f
osc
, OSCILLATOR FREQUENCY (Hz)
osc
Figure 2. Timing Resistor versus
Oscillator Frequency
Figure 3. Output Deadtime versus
Oscillator Frequency
V
CC
A = −1.0
T = 25°C
A
= 15 V
V
CC
A = −1.0
T = 25°C
A
= 15 V
V
V
2.55 V
3.0 V
2.5 V
2.5 V
2.0 V
2.45 V
0.5 ms/DIV
1.0 ms/DIV
Figure 4. Error Amp Small Signal
Transient Response
Figure 5. Error Amp Large Signal
Transient Response
100
80
60
40
20
1.2
0
V
= 15 V
V = 2.0 V to 4.0 V
CC
V
CC
= 15 V
O
R = 100 K
T = 25°C
A
1.0
0.8
0.6
0.4
0.2
0
30
60
90
L
Gain
T = 25°C
A
T = 125°C
A
Phase
T = −55°C
120
A
0
150
180
−ꢀ20
10
100
1.0 k
10 k
100 k
1.0 M
10 M
0
2.0
4.0
6.0
8.0
f, FREQUENCY (Hz)
V , ERROR AMP OUTPUT VOLTAGE (V)
O
Figure 6. Error Amp Open Loop Gain and
Phase versus Frequency
Figure 7. Current Sense Input Threshold
versus Error Amp Output Voltage
http://onsemi.com
4
ONSEMI [ ONSEMI ]
