ML4823CQ View Datasheet(PDF) - Micro Linear Corporation

Part Name

Description

Manufacturer

ML4823CQ

High Frequency Power Supply Controller

Micro Linear Corporation 

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.

ML4823

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

ISET

RT

RT

3V

CT

IQ1

Q1

5.1V

ISET

+

Q2

–

CLOCK

OUT

400µA

CLOCK OUT

TD

RAMP PEAK

CT

RAMP VALLEY

Figure 1. Oscillator Block Diagram

100k

100nF

47nF

22nF

10nF

10k

4.7nF

2.2nF

1nF

470pF

1k

0.1k

1k

10k

100k

1M 10M

FREQ (Hz)

Figure 2. Oscillator Timing Resistance vs Frequency

160

140

120

100

80

10k

1.0nF

470pF

100k

1M

FREQ (Hz)

Figure 3. Oscillator Deadtime vs Frequency

30

25

20

15

10

5

0

0.47 1.0 2.2 4.7 10.0 22 47 100

CT (nF)

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

5

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