SC1189_05 Datasheet, PDF (1/16 Pages) Semtech Corporation – Programmable Synchronous DC/DC Converter, Dual LDO Controller

SC1189
Programmable Synchronous DC/DC
Converter, Dual LDO Controller
POWER MANAGEMENT
Description
The SC1189 combines a synchronous voltage mode
controller 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^®III.
The SC1189 switching section features an integrated 5
bit D/A converter, latched drive output for enhanced noise
immunity, pulse by pulse current limiting and logic
compatible shutdown. The SC1189 switching section
operates at a fixed frequency of 200kHz, providing an op-
timum compromise between size, efficiency and cost in
the intended application areas. The integrated D/A con-
verter provides programmability of output voltage from
1.05V to 1.825V in 25mV increments with no external
components.
The SC1189 linear sections are low dropout regulators
with short circuit protection, supplying 1.25V for Vtt and
2.5V for non-GTL I/O. They can be easily adjusted to sup-
ply higher voltages e.g. 1.8V chipset.
Features
‹ ·Synchronous design, enables no heatsink solution
‹ 95% efficiency (switching section)
‹ 5 bit DAC for output programmability
‹ Designed for Intel Pentium^® III requirements
‹ 1.25V, 2.5V short circuit protected linear controllers
‹ Linear controllers adjustable to 1.8V chipset.
‹ VRM 8.5 Compliant
‹ VRM 8.4 Compliant (1.3V to 1.8V)
‹ 1.0% accuracy (1.6V to 1.8V)
‹ On Chip Power Good Signal
Applications
‹ Pentium^® III microprocessor supplies
‹ 1.050V to 1.825V microprocessor supplies
‹ Programmable triple power supplies
Simplified Application Circuit
12V
5V
+
10
1500uF
x4
0.1uF
VID25MV
VID0
VID1
VID2
VID3
EN
3.3V
U6
5 _VCC
7 _LDOEN
22 _VID25MV
21 _VID0
20 _VID1
19 _VID2
18 _VID3
16 _EN
1 _AGND
23 _LDOV
24 _GATE2
4 _LDOS2
SC1189CS
CS+ ⁹
CS- ^{8 0.1uF}
VOSENSE ¹⁷
BSTH ¹⁵
DH ¹¹
BSTL ¹⁴
DL ¹³
PGNDH ¹⁰
PGNDL ¹²
PWRGD ⁶
GATE1 ²
LDOS1 ³
2R2
2R2
+
330uF
1.8V
+
330uF
442
1.0k
2.5V
+
330uF
+
47uF
0.1uF
0.1uF
1.2uH
1.00k
OPEN
2.5mOhm
VCC_CORE
1k
5V
+
1500uF
x6
0.1uF
10k
PWRGD
Revision: July 6, 2005
1
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