HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
The oscillator frequency f
OSC
can be calculated as follows.
f
OSC
=
Here, t
1
=
t2 =
1
t
1
+ t
2
+ t
3
C
T
×
(V
H
−
V
L
)
1.1 V/R
T
C
T
×
(V
H
−
V
L
)
3
×
1.1 V/R
T
t3
≈
0.8
µs
(comparator delay time)
Since V
H
−
V
L
= 0.6 V
f
OSC
≈
1
(Hz)
0.73
×
C
T
×
R
T
+ 0.8 (µs)
At high frequencies the comparator delay causes the sawtooth wave to overshoot the 1.6 V threshold and
undershoot the 1.0 V threshold, and changes the dead-band thresholds accordingly. Select constants by
testing under implementation conditions.
3.2 V
(Internal voltage)
Current
mirror
C
T
charging
I
O
Oscillator
comparator
1.1 V
1:4
Discharg
-ing 3I
O
R
C
R
B
Sync
circuit
R
T
C
T
I
O
External circuit
V
H
= 1.6 V typ
Vref
2.5 V
R
A
SYNC
t
2
t
1
V
L
= 1.0 V typ
t
1
: t
2
= 3 : 1
Figure 1.1 Equivalent Circuit of Oscillator
Rev.2.0, Sep.18.2003, page 7 of 37