HA16116FP Datasheet, PDF (19/34 Pages) Hitachi Semiconductor – Switching Regulator for Chopper Type DC/DC Converter

HA16116FP/FPJ, HA16121FP/FPJ
7.2 Adjusting UVL Voltage (when intermittent operation is not used)
The UVL voltage setting in this IC series can be adjusted externally as shown below.
Using the relationships shown in the figure, the UVL voltage in relation to V_IN can be adjusted by changing
the relative values of V_TH and V_TL.
When the IC is operating, transistor Q₄ is off, so V_ON = 3V_BE ≈ 2.1 V. Accordingly, by connecting resistors
R_C and R_D, the voltage at which UVL is cancelled is as follows.
V_IN = 2.1 V ×
R_C + R_D
R_D
This V_IN is simply the supply voltage at which the UVL stops functioning, so in this state Vref is still below
2.5 V. In order to restore Vref to 2.5 V, a V_IN of approximately 4.3 V should be applied.
With this IC series, V_ON/OFF makes use of the V_BE of internal transistors, so when designing a power supply
system it should be noted that V_ON has a temperature dependency of around –6 mV/°C.
P.V_IN
S.V_IN
TIM
R_C
(open)
To output
stage
To latch
V_IN
To other circuitry
ON/OFF
50 kΩ
R_D
Q₁
Vref
generation
circuit
Q₂
Q₃
Q₄
Vref output
GND
On/off hysteresis circuit
3
2
Vref
1
V_OFF
1.4 V
2.5 V
V_ON
2.1 V
V_IN ≥ 4.5 V
0
012 345
V_ON/OFF
Figure 7.2 Adjusting UVL Voltage
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