5

UC1524

UC2524

UC3524

Oscillator

The oscillator controls the frequency of the UC1524 and is

formula:

f

RC

TT

′

1.18

where

where

where

f is in kHz

This results in a frequency range typically from 120Hz to

500kHz.

Blanking

The output pulse of the oscillator is used as a blanking

pulse at the output. This pulse width is controlled by the

quency control, the oscillator output pulse width may still

be increased by applying a shunt capacitance of up to

100pF from pin 3 to ground. If still greater dead-time is re-

quired, it should be accomplished by limiting the maxi-

mum duty cycle by clamping the output of the error

amplifier. This can easily be done with the circuit in Fig-

ure 1:

Synchronous Operation

When an external clock is desired, a clock pulse of ap-

proximately 3V can be applied directly to the oscillator

output terminal. The impedance to ground at this point is

approximately 2k

selected for a clock period slightly greater than that of the

external clock.

If two or more UC1524 regulators are to operated synchro-

nously, all oscillator output terminals should be tied to-

minals.

APPLICATION INFORMATION

16

V

REF

COMP

5k

9

GND

8

1N916

Figure 1. Error amplifier clamp.

Figure 2. Single-ended LC switching regulator circuit.