ML4823
FUNCTIONAL DESCRIPTION
OSCILLATOR
The ML4823 oscillator charges the external capacitor (C )
The oscillator period can be described by the following
relationship:
T
with a current (I ) equal to 3/R . When the capacitor
SET
SET
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.
T
= T
+ T
RAMP DEADTIME
OSC
where: T
= C (Ramp Valley to Peak)/I
SET
RAMP
and:
T
= C (Ramp Valley to Peak)/I
DEADTIME
Q1
I
SET
R
C
T
5.1V
R
T
3V
I
SET
160
140
120
100
80
T
+
–
Q
2
1.0nF
CLOCK
OUT
I
Q1
Q1
400µA
470pF
10k
100k
FREQ (Hz)
1M
CLOCK OUT
T
D
RAMP PEAK
Figure 3. Oscillator Deadtime vs Frequency
C
T
RAMP VALLEY
Figure 1. Oscillator Block Diagram
100k
30
25
20
15
10
5
100nF
47nF
22nF
10nF
10k
4.7nF
2.2nF
1nF
470pF
0
1k
0.1k
0.47 1.0
2.2
4.7 10.0
(nF)
22
47
100
100k
FREQ (Hz)
1k
10k
1M
10M
C
T
Figure 2. Oscillator Timing Resistance vs Frequency
Figure 4. Oscillator Deadtime vs C (3kΩ ≤ R ≤ 100kΩ)
T
T
5
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
