HA16108FP HITACHI [Hitachi Semiconductor], HA16108FP Datasheet - Page 10

• Manufacturer Part Number: HA16108FP
• Description: PWM Switching Regulator for High-performance Voltage Mode Control
• Manufacturer: HITACHI [Hitachi Semiconductor]

approximately 4 V and 5 V. PWM output also shuts down below these voltages. It follows that PWM
output will shut off whenever the Vref pin is shorted to the power supply (V
HA16107P/FP, HA16108P/FP
Vref Protection Functions: Overvoltage and Undervoltage
Vref overvoltage and undervoltage conditions are detected by the overvoltage detection circuit and UVL2
circuit. PWM output shuts down when Vref
output also shuts off when V
The following diagram shows how these protection functions operate when power comes on and goes off
(Vref < 6.45 V), and when a high external voltage is applied to the Vref pin (Vref > 6.45 V).
1. Current-Limiter Circuit
10
The current limiter pin (CL) is connected to the emitter of an npn transistor, as shown in the block
diagram. The threshold voltage is 240 mV typ. The switching speed of this circuit is approximately
100 ns from detection of overcurrent to shut-down of PWM output. Switching speed increases with the
strength of the signal input to the CL pin.
Instead of simple pulse-by-pulse current limiting, in these ICs the current limiting circuit is linked to the
timer-and-latch or ON/OFF timer circuit, and also detects the degree of overcurrent. The overcurrent
value is determined from the point at which current limiting is triggered in the ON-duty cycle. With a
large overcurrent (causing current limiting to operate even at a small ON-duty), the IC automatically
shortens the timer time.
PWM
OUT
0
Power-off,
or shorted
to ground
Power-up
IN
is turned on or off.
PWM output shut-
down region
4 V 5 V 6.45 V 8 V
UVL2
8 V. UVL2 detects undervoltage with hysteresis between
PWM output
operating region
Shorted to
power supply
Vref
OVP
10 V
PWM output
shut-down region
Vref
IN
) or ground (GND). PWM