UCC2800/2801/2802/2803/2804/2805EP

LOW POWER BICMOS CURRENT MODE PWM

SGLS135E − SEPTEMBER 2002 − REVISED DECEMBER 2007

9

POST OFFICE BOX 655303

PARAMETER MEASUREMENT INFORMATION

Figure 1

Oscillator

The UCC3800/1/2/3/4/5 oscillator generates a sawtooth waveform

on RC. The rise time is set by the time constant of RT and CT. The

fall time is set by CT and an internal transistor on-resistance of

approximately 125. During the fall time, the output is off and the

maximum duty cycle is reduced below 50% or 100% depending on

the part number. Larger timing capacitors increase the discharge

time and reduce the maximum duty cycle and frequency.

Figure 2

Error Amplifier

Gain/Phase Response

Figure 3

Figure 4

UCC1800/01/02/04 Oscillator Frequency