ML4823CS datasheet(5/9 Pages) MICRO-LINEAR

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ML4823

FUNCTIONAL DESCRIPTION

OSCILLATOR

The ML4823 oscillator charges the external capacitor (CT)

with a current (ISET) equal to 3/RSET. When the capacitor

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:

TOSC = TRAMP + TDEADTIME

where: TRAMP = C (Ramp Valley to Peak)/ISET

and:

TDEADTIME = C (Ramp Valley to Peak)/IQ1

–

5.1V

ISET

400

µA

IQ1

CLOCK

OUT

CLOCK OUT

RAMP PEAK

RAMP VALLEY

Figure 2. Oscillator Timing Resistance vs Frequency

Figure 4. Oscillator Deadtime vs CT (3kΩ ≤ RT ≤ 100kΩ)

0.47

1.0

2.2

4.7

10.0

CT (nF)

100

160

140

120

100

10k

100k

FREQ (Hz)

1.0nF

470pF

Figure 3. Oscillator Deadtime vs Frequency

Figure 1. Oscillator Block Diagram

100k

10k

0.1k

10k

100k

10M

FREQ (Hz)

100nF

47nF

22nF

10nF

4.7nF

2.2nF

1nF

470pF

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