BU90002GWZ Datasheet, PDF (17/24 Pages) Rohm – Step-down Switching regulators with Built-in Power MOSFET

BU9000xGWZ series
Datasheet
●PC Board layout
The suggested PCB layout for the BU9000xGWZ are shown in Figure. The following guidelines should be used to ensure a
proper layout.
1) The input capacitor CIN should be connect as closely possible to VIN pin and GND pin.
2) From the output voltage to the FB pin line should be as separate as possible.
3) COUT and L should be connected as closely as possible. The connection of L to the LX pin should be as short as
possible.
Figure 50. PCB layout
●External parts selection
Inductor selection
The inductance significantly depends on output ripple current. As shown by following equation, the ripple current decreases
as the inductor and/or switching frequency increase.
(VIN-VOUT)×VOUT
⊿IL=
L×VIN×f
f: switching frequency L: inductance ⊿IL: inductor current ripple
As a minimum requirement, the DC current rating of the inductor should be equal to the maximum load current plus half of
the inductor current ripple as shown by the following equation.
ILPEAK= IOUTMAX +
⊿IL
2
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TSZ22111・15・001
17/21
TSZ02201-0F2F0AG00010-1-2
04.Jul.2012 Rev.001