Datasheet

UCC25705, UCC25706, UCC35705, UCC35706
HIGH-SPEED VOLTAGE MODE PULSE WIDTH MODULATOR
SLUS473B -- NOVEMBER 1999 -- REVISED OCTOBER 2010
9
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FUNCTIONAL DESCRIPTION
component selection for oscillator without duty cycle clamp (MODE = 0)
For a power converter with the following specifications:
D V
IN(min)
=18V
D V
IN(max)
=75V
D V
IN(shutdown)
=15V
D F
OSC
=1MHz
With these specifications,
V
FF(min)
=
18
15
= 1.2 V
(1) Pick C
T
= 220 pF
(2) Calculate R
T
.
R
T
=
V
IN(min)
V
FF(min)
×

1
F
OSC
− 75 ns

C
T
TYPICAL CHARACTERISTICS
Figure 4
--50 --25 0 25 50 75 100 125
Temperature
8.0
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
UCC35705 UVLO THRESHOLDS
vs
TEMPERATURE
°C
UVLO -- Thresholds -- V
Figure 5
--50 --25 0 25 50 75 100 125
Temperature
7
8
9
10
11
12
13
°C
UVLO -- Thresholds -- V
UCC35706 UVLO THRESHOLDS
vs
TEMPERATURE