HA16107P Datasheet, PDF (12/40 Pages) Hitachi Semiconductor – PWM Switching Regulator for High-performance Voltage Mode Control

HA16107P/FP, HA16108P/FP
2. Use of ON/OFF Timer Pin (HA16108)
 External Circuit
ION
16
+
IOFF
16 µA
from CML
OVP with
latch timer
4 µA
HA16108
 ON/OFF Timer Operation
7.0 V ^VTHH
t_OFF
t_ON
1.2 V ^VTHL
0V
t
OCL detected PWM
OCL detected
(PWM output on) output
(PWM output on)
shut down
t_ON
≈
(0.9
−
C
Du)
×
×
5.8 V
16 µA −
4
µA
t_OFF ≈
C
× 5.8 V
4 µA
Pulse-by-pulse current limiting
Notes: 1. C is the capacitance of an external timing capacitor connected between this pin and ground.
2. Du is the ON-duty of the PWM output when overcurrent limiting is triggered.
3. The values of t_ON and t_OFF for TL can be determined by the same equations as given for
the ON/OFF timer, except that 5.8 V (V_THH − V_THL) becomes V_THH = 7 V.
4. If the timer goes off during soft start or in the undervoltage lockout region, after recovery,
output will come on after the soft-start time or after the rise time to the undervoltage lockout
release point, which is determined by the time constant.
Rev.4.00 Jun 15, 2005 page 12 of 39