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SC1186CSW

PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL LOW DROPOUT REGULATOR CONTROLLER

Semtech Corporation 

PRELIMINARY - December 2, 1999

PROGRAMMABLE SYNCHRONOUS DC/DC

CONVERTER, DUAL LOW DROPOUT

REGULATOR CONTROLLER

SC1186

4) The Output Capacitor(s) (Cout) should be located

as close to the load as possible, fast transient load

currents are supplied by Cout only, and connections

between Cout and the load must be short, wide cop-

per areas to minimize inductance and resistance.

5) The SC1186 is best placed over a quiet ground

plane area, avoid pulse currents in the Cin, Q1, Q2

loop flowing in this area. PGNDH and PGNDL should

be returned to the ground plane close to the package.

The AGND pin should be connected to the ground

side of (one of) the output capacitor(s). If this is not

possible, the AGND pin may be connected to the

ground path between the Output Capacitor(s) and the

Cin, Q1, Q2 loop. Under no circumstances should

AGND be returned to a ground inside the Cin, Q1, Q2

loop.

6) Vcc for the SC1186 should be supplied from the

5V supply through a 10Ω resistor, the Vcc pin should

be decoupled directly to AGND by a 0.1µF ceramic

capacitor, trace lengths should be as short as possi-

ble.

7) The Current Sense resistor and the divider across

it should form as small a loop as possible, the traces

running back to CS+ and CS- on the SC1186 should

run parallel and close to each other. The 0.1µF ca-

pacitor should be mounted as close to the CS+ and

CS- pins as possible.

8) Ideally, the grounds for the two LDO sections

should be returned to the ground side of (one of) the

output capacitor(s).

5V

+

Vout

+

Currents in various parts of the power section

© 1999 SEMTECH CORP.

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