鈥?/div>
SETTING THE SWITCHING FREQUENCY (PROGRAMMING THE CLOCK OSCILLATOR)
The TPS40074 has independent clock oscillator and PWM ramp generator circuits. The clock oscillator serves as
the master clock to the ramp generator circuit. Connecting a single resistor from RT to ground sets the switching
frequency of the clock oscillator. The clock frequency is related to R
T
by:
R
T
+
f
SW
(kHz)
1
17.82
10
*6
*
23
kW
(3)
MINIMUM OUTPUT VOLTAGE
vs
FREQUENCY
5.0
4.5
V
OUT
鈭?/div>
Output Voltage
鈭?/div>
V
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
100
V
IN
= 28 V
V
IN
= 24 V
V
IN
= 18 V
V
IN
= 15 V
V
IN
= 12 V
V
IN
= 10 V
V
IN
= 8 V
V
IN
= 5 V
200
300 400 500 600 700 800 900 1000
f
OSC