ML4825

5

FUNCTIONAL DESCRIPTION

OSCILLATOR

voltage reaches the upper threshold (Ramp Peak), the

comparator changes state and the capacitor discharges to

the lower threshold (Ramp Valley) through Q1. While the

capacitor is discharging, Q2 provides a high pulse.

The oscillator period can be described by the following

relationship:

where:

t

C Ramp Valley to Peak

I

RAMP

SET

= ()

and:

t

C Ramp Valley to Peak

I

DEADTIME

Q

= ()

1

Figure 1. Oscillator Block Diagram

3V

5.1V

Q1

CLOCK

RAMP PEAK

RAMP VALLEY

4

6

5

+

–

100k

10k

1k

FREQUENCY (Hz)

100

1k

10k

1M

100k

100nF

47nF

22nF

0nF

4.7nF

2.2nF

1nF

470pF

160

140

120

100

80

FREQUENCY (Hz)

10k

100k

1M

1.0nF

470pF

4.70

2.20

1.00

0.47

0.22

0.10

0.047

CT (nF)

0.47

2.2

100

22

1.0

4.7

47

10.0

Figure 2. Oscillator Timing Resistance vs Frequency

Figure 3. Oscillator Deadtime vs Frequency