BD9610AMUV-E2 Datasheet, PDF (19/30 Pages) Rohm – 60V Synchronous Step-down Switching Regulator(Controller type)

BD9610AMUV
●Selection of Components Externally Connected
(1)INDUCTOR
It is recommended that the inductor which satisfying the absolute
maximum current and having low dc resistance and shielded type.
The Inductance is affected to the ripple current
and cause Vo ripple voltage.
Increasing the inductance or the switching frequency
make the ripple current small.
Δ IL
Ipeak = Iout ＋ 1/2×⊿IL [A]
(1)
Fig.36 Inductor Current
⊿IL= (Vin-Vout) / L ×(Vout / Vin) × (1 / fosc) [A]
(2)
(⊿IL：Inductor ripple current、fosc : Switching frequency)
Generally, ⊿IL is chosen so that the converter enters discontinuous mode at 20-40% of nominal load.
If the inductor current is over the maximum current, the inductor may cause saturation and the efficiency become
worse and sometime the DC/DC may cause an oscillation. It is very important to select the large absolute current
inductor with enough dilating.
(2)COUT
It is recommended to choice the small ESR capacitor for decreasing Vout ripple voltage.
Also it is important to use high absolute voltage capacitor with care for DC bias characteristic.
The Vout ripple voltage is calculated by the following equation.
Vripple = ⊿IL×1 / (2π x f x Cout) + ⊿IL×Resr
(3)
If the capacitance of Cout is too large, it is not able to start up. Please refer the following equation.
Cout ≦ tss × ( Iocp – Iout ) / Vout
(4)
（tss：soft start time, Iocp：OCP detect current）
(3)SETTING OF VOUT
The reference voltage of the ERROR AMP is set to 0.8V.
The Vout voltage is calculated by the following equation
VOUT = (R1+R2) / R2 ×0.8[V]
VOUT
R1
R2
(5)
ERROR AMP
INV
VNON
0.8V
(4)FET
Fig.37 Vout setting
It is needed to select high dilated FET because of the short current or the high switching spike noise
Please choise the low Ciss or low Qg FET considering for the low noise and high efficiency application.
Also It should be care for gate bias voltage, the BD9610AMUV drive the FET by 10V driver.
(5)CBST
A capacitor connected from BST to LX is the power supply for high side FET driver. It should be connected the
ceramic capacitor 0.47uF in the general application.
(6)CIN
It should be careful for the absolute maximum voltage, ripple current and low ESR devise.
Please refer the Irms equation for calculating ripple current.
Irms = Iout × √ (Vout・(Vin - Vout) / Vin)
(6)
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TSZ22111・14・001
19/27
TSZ02201-0Q1Q0AJ00010-1-2
24.OCT.2014 Rev.002