PROGRAMMABLE SYNCHRONOUS DC/DC

CONVERTER, DUAL LOW DROPOUT

REGULATOR CONTROLLER

© 1999 SEMTECH CORP.

PRELIMINARY - January 6, 1999

652 MITCHELL ROAD NEWBURY PARK CA 91320

SC1185

SC1185A

9

Vout

5V

+

+

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 SC1185 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 SC1185 should be supplied from the 5V

supply through a 10

Ω resistor, the Vcc pin should be

decoupled directly to AGND by a 0.1

µF ceramic ca-

pacitor, trace lengths should be as short as possible.

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 SC1185 should

run parallel and close to each other. The 0.1

µF 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).

Currents in various parts of the power section