BD9610AMUV-E2 Datasheet, PDF (13/30 Pages) Rohm – 60V Synchronous Step-down Switching Regulator(Controller type)

BD9610AMUV
(6) PWM / BOOST (PRE-CHARGE MODE)
It should be needed to charge the CBST (BST-LX) for driving high-side N-channel FET
The CBST capacitor is charged to the voltage of REG10 by turning on the low side FET through the internal FET
switch between REG10 and BST.
The maximum on duty does not reach to 100% because of the LG minimum on pulse. It makes possible to charge
the CBST even if the voltage of the FB pin is over 2.0V (It is the high voltage of the internal ramp wave.) and the HG
is always going to output the High. If the voltage of Vin and Vout are becoming close, the voltage of the Vout doesn’t
become equal to the voltage of the Vin.
※About Max Duty
The BD9610AMUV turns off for almost 350nsec in the every turn.(=High side minimum off pulse :HGmin)
This time ( about 350ns) consists of the LG min pulse (about 100ns) and of the anti cross conduction time among the
HG and the LG (each 100ns).
The Max ON Duty is calculated in the following equation.
D(on) = ( T –Toff) / T
[T：Switching cycle(1/FOSC)、Toff：OFF time(≒350ns typ.)]
※PRE-CHARGE MODE
The BD9610AMUV operates in the pre-charge mode during the time for charging the CBST at the start-up, dropping
the voltage of CBST and the releasing protect function (UVLO, TSD, OCP hiccup-mode) for charging the CBST in
advance. In this mode, the CBST is charged by the LG on pulse that is limited to almost 300ns at every turn. This
mode is switched to the normal switching mode by being detected to release the BSTUVLO.
(7)STAND-BY
It is possible to make the value of the quiescent current 0uA by turning off the CTL pin.
The all of the function is terminated for example REG5 and REG10 in this mode.
(8)UVLO
The UVLO circuits shut down HG, LG, SS and FB, when the voltage of VCC or REG10 or REG5 are under the each
UVLO threshold (VCC<9V, REG10<8V, REG5<4.5V). And there are voltage hysteresis at VCC, REG10 and REG5
( VCC:0.5V, REG10:0.5V, REG5:0.2V). When the UVLO is released, soft-start starts after the voltage of RTSS is over
0.5V. Case of being needed the quick start-up, please adjust the capacitance of the CRTSS.
The BST_UVLO is also built t between BST and LX. When the BST_UVLO is detected, HG, SS and FB are shut
down and the BD9610AMUV shift to the pre-charge mode. (CBST is charged by LG pulse(t≅ 300ns))
(9)TSD
The TSD is the protection for the IC chip against abnormal temperature (over Tjmax(150deg)). The TSD works at
almost 175deg, so It doesn’t work in the normal operating temperature range. If the chip is cool down, TSD is
automatically released at almost 150deg. Under the TSD protection, HG, LG, SS and FB are shut down like the
UVLO.
(10)LG short protection
When the LG pin short to GND, an exceptional large current flow in the BD9610AMUV. (The DC/DC is able to output
as a diode rectifier mode by the body diode of the low side Nch-FET.)
For this case, the BD9610AMUV checks to turn LG on after the PWM low output in every cycle. If LG doesn’t turn on,
the DC/DC will be shut down.
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TSZ22111・14・001
13/27
TSZ02201-0Q1Q0AJ00010-1-2
24.OCT.2014 Rev.002