BD8162AEKV Datasheet, PDF (14/30 Pages) Rohm – Multi-channel System Power Supply IC + Gamma Buffer

BD8162AEKV
(2.2) Selecting I/O capacitors
To select I/O capacitors, refer to information in Section (1.3).
However, the output ripple voltage of the step-down DC/DC converter is obtained by the following equation.
Δ V_PP
ΔI_L  R_ESR
 ^{ΔI L}
2C_O
 ^VO
V_CC

1
f
[V ]
(2.3) Output rectifier diode setting
For the rectifier diodes to be used as the output stage of the DC/DC converter, it is recommended to use Schottky
diodes. Select diodes with careful attention paid to the maximum inductance current, maximum output voltage, and
power supply voltage.
Maximum inductance current: IOMAX + ΔIL
2
Power supply voltage:
VCC
< Rated current of diode
< Rated voltage of diode
In addition, since each parameter has variations in current and voltage of 30% to 40%, design systems with sufficient
margin.
(2.4) Output voltage setting
Set output voltage using the following equation with feedback resistance composed of R21 and R22.
R21 R22
V_O  _R22 V_FB [V ]
Where:
VFB: Set to 1.25 for the step-down DC/DC converter (FB2) and 0.9 for the sync rectification step-down DC/DC
converter (FB3).
It is recommended to apply a setting range of 10kΩ to 330kΩ. Setting the feedback resistance to not more than 10kΩ
will result in degraded voltage efficiency, while setting it to not less than 330kΩ will result in higher offset voltage due
to an input bias current of 0.1µA (Typ) of the internal error amplifier.
(2.5) Phase compensation setting
For details of phase compensation setting, refer to information in Section (1.6).
(2.6) Duty cycle limit setting
For details of duty cycle limit setting, refer to information in Section (1.7).
For step-down converters, however, the range normally used comes to the following:
Max On duty cycle =
VOMAX
VCCMIN
< Max set duty cycle
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TSZ22111・15・001
14/26
TSZ02201-0323AAF00690-1-2
15.Feb.2016 Rev.001