HA16120 RENESAS [Renesas Technology Corp], HA16120 Datasheet - Page 7

• Manufacturer Part Number: HA16120
• Description: Switching Regulator for Chopper Type DC/DC Converter
• Manufacturer: RENESAS [Renesas Technology Corp]

HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
The oscillator frequency f
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.
Rev.2.0, Sep.18.2003, page 7 of 37
Here,
Since
R
I
O
T
1.1 V
f
t
t 2 =
t 3
V
f
1
OSC
OSC
Current
mirror
H
=
0.8 s (comparator delay time)
=
V
C
L
C
0.73
3
T
= 0.6 V
T
t
External circuit
OSC
1
1.1 V/R
+ t
1.1 V/R
(V
(V
can be calculated as follows.
1
2
H
H
Figure 1.1 Equivalent Circuit of Oscillator
C
+ t
T
T
3
V
V
1 : 4
T
L
L
1
R
)
)
T
+ 0.8 ( s)
(Internal voltage)
Discharg
-ing 3I
C
t
t
1
2
V
T
H
I
charging
O
O
C
= 1.6 V typ
T
(Hz)
3.2 V
Oscillator
comparator
V
L
= 1.0 V typ
t
R
1
C
: t
2
= 3 : 1
R
R
A
B
2.5 V
Vref
SYNC
circuit
Sync