sc1189 Semtech Corporation, sc1189 Datasheet - Page 8

• Manufacturer Part Number: sc1189
• Description: Sc1189 Programmable Synchronous Dc/dc Converter, Dual Ldo Controller
• Manufacturer: Semtech Corporation

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 copper areas to mini-
mize inductance and resistance.
5) The SC1189 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 circum-
stances should AGND be returned to a ground inside the
POWER MANAGEMENT
Layout Guidelines (Cont.)
2007 Semtech Corp.
5V
+
8
Cin, Q1, Q2 loop.
6) Vcc for the SC1189 should be supplied from the 5V
supply through a 10
decoupled directly to AGND by a 0.1 F ceramic capacitor,
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 run-
ning back to CS+ and CS- on the SC1189 should run par-
allel and close to each other. The 0.1 F capacitor 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 Power Section
+
resistor, the Vcc pin should be
Vout
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SC1189