UC3844, 45 UC2844, 45
Figure 1. Timing Resistor versus
Oscillator Frequency
100
% DT, PERCENT OUTPUT DEADTIME
RT, TIMING RESISTOR (k
Ω
)
50
20
10
5.0
2.0
VCC = 15 V
TA = 25°C
Figure 2. Output Deadtime versus
Oscillator Frequency
75
70
65
CT = 10 nF
5.0 nF
1.0 nF
2.0 nF
60
55
50
10 k
500 pF
NOTE: Output switches
at one–half the oscillator
frequency.
100 pF
200 pF
1.0
10 k
20 k
50 k
100 k
200 k
500 k
1.0 M
20 k
50 k
100 k
200 k
500 k
1.0 M
fosc, OSCILLATOR FREQUENCY (Hz)
fosc, OSCILLATOR FREQUENCY (Hz)
Figure 3. Error Amp Small Signal
Transient Response
VCC = 15 V
AV = –1.0
TA = 25°C
Figure 4. Error Amp Large Signal
Transient Response
VCC = 15 V
AV = –1.0
TA = 25°C
2.55 V
3.0 V
20 mV/DIV
2.5 V
2.5 V
2.45 V
0.5
µs/DIV
2.0 V
1.0
µs/DIV
Figure 5. Error Amp Open Loop Gain and
Phase versus Frequency
Vth, CURRENT SENSE INPUT THRESHOLD (V)
A VOL , OPEN LOOP VOLTAGE GAIN (dB)
100
80
Gain
60
40
Phase
20
0
– 20
10
120
150
100
1.0 k
10 k
100 k
1.0 M
180
10 M
VCC = 15 V
VO = 2.0 V to 4.0 V
RL = 100 K
TA = 25°C
0
30
60
90
φ
EXCESS PHASE (DEGREES)
,
1.2
Figure 6. Current Sense Input Threshold
versus Error Amp Output Voltage
VCC = 15 V
1.0
0.8
0.6
TA = 125°C
0.4
0.2
0
TA = –55°C
TA = 25°C
0
f, FREQUENCY (Hz)
2.0
4.0
6.0
VO, ERROR AMP OUTPUT VOLTAGE (V)
8.0
4
MOTOROLA ANALOG IC DEVICE DATA
200 mV/DIV
ONSEMI [ ON SEMICONDUCTOR ]
