ML4810, ML4811

6

Figure 4. Switching Current and Pin 4 Voltage — Normal

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

Figure 7. Oscillator Timing Resistance vs Frequency

Figure 8. Oscillator Deadtime vs Frequency

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. A

discharge of the oscillator con be initiated by applying a

high level to the Sync pin. A short pulse of a frequency

higher than the oscillator’s free running frequency can be

used to synchronize the ML4811 to an external clock. The

greater.

I(1)

V(1)

I(1)

V(1)

Figure 5. Switching Current and Pin 4 Voltage — Load Fault

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

CLOCK

OUT

Q2

5V

3V

SYNC

Q1

CLOCK

RAMP PEAK

RAMP VALLEY

5

7

6

10

+

–

Figure 6. Simplified Oscilator Block Diagram and Timing