SC1185_05 Datasheet, PDF (1/14 Pages) Semtech Corporation – Programmable Synchronous DC/DC

POWER MANAGEMENT
Description
The SC1185 combines a synchronous voltage mode con-
troller with two low-dropout linear regulators providing
most of the circuitry necessary to implement three DC/
DC converters for powering advanced microprocessors
such as Pentium^® II .
The SC1185 switching section features an integrated 5
bit D/A converter, pulse by pulse current limiting, inte-
grated power good signaling, and logic compatible shut-
down. The SC1185 switching section operates at a fixed
frequency of 140kHz, providing an optimum compromise
between size, efficiency and cost in the intended appli-
cation areas. The integrated D/A converter provides pro-
grammability of output voltage from 2.0V to 3.5V in
100mV increments and 1.30V to 2.05V in 50mV incre-
ments with no external components.
The SC1185 linear sections are low dropout regulators
supplying 1.5V for GTL bus and 2.5V for non-GTL I/O.
The Reference voltage is made available for external lin-
ear regulators.
Typical Application Circuit
SC1185 & SC1185A
Programmable Synchronous DC/DC
Converter, Dual LDO Controller
Features
Synchronous design, enables no heatsink solution
95% efficiency (switching section)
5 bit DAC for output programmability
On chip power good function
Designed for Intel Pentium^® ll requirements
1.5V, 2.5V @ 1.25% for linear section
1.265V ± 1.5% Reference available
24-lead SO package. Lead free option available.
Lead free product is fully WEEE and RoHS
compliant.
Applications
Pentium^® ll microprocessor supplies
Flexible motherboards
1.3V to 3.5V microprocessor supplies
Programmable triple power supplies
12V
5V
+
10
1500uF
x4
0.1uF
+
4.7uF
PWRGOOD
VID0
VID1
VID2
VID3
VID4
EN
3.3V
0.1uF
5 _VCC
7 _PWRGOOD
CS+ ⁹
CS- ⁸
0.1uF
22 _VID0
VOSENSE ¹⁷
IRLR3103N
21 _VID1
20 _VID2
BSTH ¹⁵
DH ¹¹
2R2
19 _VID3
BSTL ¹⁴
IRLR3103N
18 _VID4
16 _EN
DL ¹³
PGNDH ¹⁰
2R2
1 _AGND
PGNDL ¹²
23 _LDOV
REF ⁶
24 _GATE2
GATE1 ²
4 _LDOS2
LDOS1 ³
SC1185CS
330uF
+
IRLR024N
+
330uF
1.5V
2.5V
+
330uF
IRLR024N
1.9uH
1.00k
2.32k
5mOhm
VCC_CORE
1k
12V
+
3.3V
1500uF
x6
0.1uF
3
8
+
2_-
1
LM358
4
IRLR024N
VLIN3
+
330uF
Revision: July 28, 2005
1
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