SC1173 Semtech Corporation, SC1173 Datasheet - Page 9

• Manufacturer Part Number: SC1173
• Description: PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH LOW DROPOUT REGULATOR CONTROLLER
• Manufacturer: Semtech Corporation

October 25, 1999
© 1999 SEMTECH CORP.
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 SC1172/3 is best placed over a quite 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 SC1172/3 should be supplied from the
Currents in various parts of the power section
5V
+
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
5V supply through a 10 resistor, the Vcc pin should
be decoupled directly to AGND by a 0.1 F 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 SC1172/3 should
run parallel and close to each other. The 0.1 F ca-
pacitor should be mounted as close to the CS+ and
CS- pins as possible.
8) Ideally, the ground for the LDO section should be
returned to the ground side of (one of) the switching
section output capacitor(s).
652 MITCHELL ROAD NEWBURY PARK CA 91320
+
Vout
SC1172/3
9