BD9361GUL Datasheet, PDF (19/27 Pages) Rohm – 6ch Internal Power MOSFET System Switching Regulator + 1ch LDO

BD9361GUL
●Setting method of IC peripheral components
(1) Design of feedback resistor constant
VOUT5
R1
ERROR AMP
INV
R2
VREF
0.8V
CH5 output voltage
(R1+R2)
Vo=
×0.8 [V] ・・・ (1)
R2
CH6 output current
INV6
Io= _R3 [A] ・・・ (2)
Fig25. Feedback resistor setting method
VOUT6
ERROR AMP6
INV6
R3
VREF
12.5,mV~400mV
(a)CH5 setting
The reference voltage of CH5’s ERROR AMP is 0.8V inside IC. Please refer to Formula (1) for determining the output
voltage. This IC has phase compensation. R1 and R2 are recommended as more than 100kΩ.
(b)CH6 setting
LED current is decided (2) formula. Please decide R3 value for LED current range. It is possible to control Dimming by only
serial I/F.
(2) Points for attention in terms of PCB layout of base-plate
○For a switching regulator, in principle a large current transiently flows through the route of power supply – coil – output
capacitor. Ensure that the wiring impedance is lowered as much as possible by making the pattern as wide as possible and
the layout as short as possible.
○Interference of power supply noise with feedback terminals (Vo, INV) may cause the output voltage to oscillate.
Ensure that the power supply noise’s interference is avoided by making the wiring between feedback resistor and feedback
terminal as short as possible.
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19
TSZ22111・14・001
TSZ02201-0Q2Q0A400010-1-2
2011.12.22 Rev.001