BD9610AMUV-E2 Datasheet, PDF (11/30 Pages) Rohm – 60V Synchronous Step-down Switching Regulator(Controller type)

BD9610AMUV
●Function Description
(1)REG5 REGULATOR
It is used for internal power supply and the reference voltage. It can load more less than 2mA.
Please connect a ceramic capacitor (CREG5=0.1uF) between REG5 and GND.
(2)REG10 REGULATOR
This is a regulator for a low side DRV and charge the BST-LX capacitor through the internal FET switch. Please
connect a ceramic capacitor (CREG10=1.0uF) between REG10 and GND.
This regulator limites load current about 20mA, When REG10 pin short to GND. Because of this function,
(3)SOFT START
For preventing rush current or overshoot, The reference voltage should be ramped startup.
The reference voltage used for the startup is derived in the following manner. A capacitor (CSS) is connected to
the SS pin. There is a ramped voltage generated at this pin be charging CSS with a source current (ISS=1uA).
The soft-start time is decided by the time to reach SS voltage to 0.8V.
tss = (CSS×VNON) / ISS
(ex.)CSS=0.01uF
tss = (0.01u×0.8)/1u = 8 [ms]
Before the beginning of soft start, It takes the start-up time for RTSS described next state.
(4)OSCILLATOR (RT、RTSS、CLKOUT)
The switching frequency of the oscillator is set by a single resistor RRT to ground.
The clock frequency is related to RRT by the following equation and the relationship is charted in fig.26
The amplitude of the triangle wave of the oscillator is 1.5V-2.0V.
FOSC = 1 / ( 50e-6 × RRT ) [kHz]
1000
（RRT: RT resister [kΩ]）
100
10
10
100
RRT (kΩ)
1000
Fig.26 Switching frequency
vs
RRT resistance
The case of not using the synchronizing to an external supply, the RTSS terminal outputs the internal reference
voltage (0.5V) through the internal voltage buffer. And the RT terminal is the buffer of the RTSS voltage. A 0.01uF
ceramic capacitor should be connected from this RTSS to ground.
When the UVLO is going to be released, the RTSS pin is quickly charged up to VRTSS=0.45V by the source current
(IRTSS=100uA) as a pre-charge function, because CRTSS is discharged during UVLO.
If the voltage of RTSS pin is reached to 0.45V, the UVLO is released and soft start function is started.
It takes this charging time for start-up of DC/DC to begin charging the CSS.
(ex.)CRTSS=0.01uF
TRTSS= (0.01uF×0.50V) / 100uA = 50 [us]
The CLKOUT pin outputs a square wave which synchronized to internal oscillator for a clock of master-slave
synchronizing function.
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TSZ22111・14・001
11/27
TSZ02201-0Q1Q0AJ00010-1-2
24.OCT.2014 Rev.002