BD9757MWV_10 Datasheet, PDF (13/24 Pages) Rohm – Switching Regulator IC

BD9757MWV
Technical Note
10. Nch DRIVER , Pch DRIVER
It is a CMOS inverter type of output circuit to drive both built-in and external Nch,Pch FET.
11. Load switch
It is a circuit, mounted in CH7, 8, to control the Load switch. HS78H terminal (36pin) is input terminal, and the HS67
and HS78 terminals (40,37pin) are output terminals.
This control circuit can prevent the rush current at the time of switch ON because the soft start starts functioning at the
time of start-up. In addition, this Load switch is provided with OCP function to prevent the IC from damage.
Ensure that the IC is used within Load switch’s rated current when used normally.
12. ON/OFF LOGIC
It is the voltage applied to STB terminal and can control the ON/OFF of CH1 ~ CH7.
If the voltage more than 1.5V is applied, then it becomes ON, but if open or 0V is applied, then it becomes off,
furthermore, it all the channels are turned off, then the whole IC will be in standby state. In addition, STB13 ~ STB7
terminals contain respectively a built-in pull-down resistor of about 400kΩ. UPIC8 is the input terminal of the start signal
and the light control signal of CH8. It becomes High if the voltage more than 2.1V is applied and becomes Low if the
voltage less than 0.4V is applied. In addition, UPIC8 terminal contains a built-in pull-down resistor of about 50kΩ.
13. SOFT START
It is a circuit to apply the soft start to the output voltage of DC/DC converter and prevent the rush current at the start-up.
Soft start time varies with the channels.
a. CH1 ・・・・・ Reaches the target voltage in 3.0 msec.
b. CH3,4 ・・・・・ Reaches the target voltage in 2.2 msec.
c. CH2,5,6 ・・・・・ Reaches the target voltage in 4.4 msec.
d. CH7,8 ・・・・・ Reaches the target voltage in 5.4 msec.
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13/20
2010.11 - Rev.A