HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
6. Usage of ON/OFF Pin
This pin is used for the following purposes:
•
•
•
To shut down the IC while its input power remains on (power management)
To externally alter the UVL release voltage
With the timer (TM) pin, to operate in intermittent mode during overcurrent (see next section)
6.1 Shutdown by ON/OFF Pin Control
The IC can be shut down safely by bringing the voltage at the ON/OFF pin below about 0.7 V (the internal
VBE value). This feature can be used in power supply systems to save power. When shut down, the
HA16114 draws a maximum current (IOFF) of 10 µA, while the HA16120 draws a maximum 150 µA. The
ON/OFF pin sinks 290 µA (Typ) at 5 V, so it can be driven by TTL and other logic ICs. If intermittent
mode will also be employed, use a logic IC with an open-collector or open-drain output.
IIN
VIN
RA
RB
VIN
External logic IC
To other circuitry
Off On
TM
ON/
To latch
10 kΩ
3VBE
Q1
Vref
Vref
output
reference
Switch
CON/
+
−
Q2
Q3
On/off hysteresis circuit
GND
HA16114,
HA16120
Figure 6.1 Shutdown by ON/OFF Pin Control
6.2 Adjustment of UVL Voltages (when not using intermittent mode)
These ICs permit external adjustment of the undervoltage lockout voltages. The adjustment is made by
changing the undervoltage lockout thresholds VTH and VTL relative to VIN, using the relationships shown in
the accompanying diagrams.
When the IC is powered up, transistor Q3 is off, so VON is 2VBE, or about 1.4 V. Connection of resistors RC
and RD in the diagram makes undervoltage lockout release at:
RC + RD
VIN = 1.4 V ×
RD
This VIN is the supply voltage at which undervoltage lockout is released. At the release point Vref is still
below 2.5 V. To obtain Vref = 2.5 V, VIN must be at least about 4.3 V.
Since V
operates in relation to the base-emitter voltage of internal transistors, V has a temperature
ON
ON/OFF
coefficient of approximately –4 mV/°C. Keep this in mind when designing the power supply unit.
When undervoltage lockout and intermittent mode are both used, the intermittent-mode time constant is
shortened, so the constants of external components may have to be altered.
Rev.2.0, Sep.18.2003, page 15 of 37
RENESAS [ RENESAS TECHNOLOGY CORP ]
