HA16120 RENESAS [Renesas Technology Corp], HA16120 Datasheet - Page 14

• 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 relation between Vref and the ADJ pin enables Vref to be trimmed by inserting one external resistor
(R
resistance ratio. Vref is then determined by the combined resistance ratio of the internal R
external R
Where, R
Although Vref can be trimmed by R
better to use two resistors having identical temperature coefficients. Vref can be trimmed in the range of
2.5 V ± 0.2 V. Outside this range, the bandgap circuit will not operate and the IC may shut down.
5.3 Vref Undervoltage Lockout and Overvoltage Protection
The undervoltage lockout (UVL) function turns off PWM pulse output when the input voltage (V
In these ICs, this is done by monitoring the Vref voltage, which normally stays constant at approximately
2.5 V. The UVL circuit operates with hysteresis: it shuts PWM output off when Vref falls below 1.7 V,
and turns PWM output back on when Vref rises above 2.0 V. Undervoltage lockout also provides
protection in the event that Vref is shorted to ground.
The overvoltage protection circuit shuts PWM output off when Vref goes above 6.8 V. This provides
protection in case the Vref pin is shorted to V
UVL Voltage
V
V
Rev.2.0, Sep.18.2003, page 14 of 37
H
L
3
) between the Vref and ADJ pins and another (R
R
Vref = V
A
B
3
: parallel resistance of R
: parallel resistance of R
and R
PWM
output
Vref (V typ)
2.0 V
1.7 V
ADJ
4
Figure 5.4 Vref Undervoltage Lockout and Overvoltage Protection
.
External
resistors
R
PWM
output
off
A
R
+ R
B
1.7 2.0
B
Figure 5.3 Trimming of Reference Voltage
V
3.6 V
3.3 V
R
R
IN
3
4
(V typ)
1
2
and R
and R
ADJ
Vref
3
2.5
or R
PWM output on
3
4
4
Description
V
V
IN
alone, to decrease the temperature dependence of Vref it is
IN
IN
or another high-voltage source.
increasing: UVL releases; PWM output starts
decreasing: undervoltage lockout; PWM output stops
R
R
1
2
4
Internal
resistors
) between the ADJ pin and ground, to change the
5.0
6.8
PWM output off
10
R
R
A
B
=
=
R
R
R
R
1
2
1
2
+ R
+ R
R
R
3
4
3
4
Vref
(V)
1
and R
IN
) is low.
2
and