HA16120 RENESAS [Renesas Technology Corp], HA16120 Datasheet - Page 13

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

HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
5. Voltage Reference (Vref = 2.5 V)
5.1 Voltage Reference
A bandgap reference built into the IC (see figure 5.1) outputs 2.5 V ± 50 mV. The sawtooth oscillator,
PWM comparator, latch, and other internal circuits are powered by this 2.5 V and an internally-generated
voltage of approximately 3.2 V.
The voltage reference section shut downs when the IC is turned off at the ON/OFF pin as described later,
saving current when the IC is not used and when it operates in intermittent mode during overcurrent.
5.2 Trimming the Reference Voltage (Vref and ADJ pins)
Figure 5.2 shows a simplified circuit equivalent to figure 5.1. The ADJ pin in this circuit is provided for
trimming the reference voltage (Vref). The output at the ADJ pin is a voltage V
generated by the bandgap circuit. Vref is determined by V
follows:
The design values of R
If trimming is not performed, the ADJ pin open can be left open.
Rev.2.0, Sep.18.2003, page 13 of 37
Vref = V
ADJ
Figure 5.2 Simplified Diagram of Voltage Reference Circuit
1
R
and R
1
R
+ R
2
Sub bandgap circuit
Main bandgap circuit
2
2
are 25 kΩ with a tolerance of ±25%.
Vref
ADJ
V
IN
Figure 5.1 Vref Reference Circuit
1.25 V
ON/
+
R
R
OFF
1
2
25 k
(typ)
25 k
(typ)
V
1.25 V (typ)
+
BG
1.25 V
ADJ
(bandgap voltage)
and the ratio of internal resistors R
25 k
25 k
V
3.2 V
Vref
2.5 V
ADJ
IN
ADJ
of 1.25 V (Typ)
1
and R
2
as