
POWER MANAGEMENT
Description
1
www.semtech.com
SC2659
Programmable Synchronous DC/DC
Hysteretic Controller with VRM 8.5 VID Range
Features
Applications
Revision: December 10, 2003
The SC2659 is a synchronous-buck switch-mode con-
troller designed for use in single ended power supply ap-
plications where efficiency is the primary concern. The
controller is a hysteretic type, with a user selectable hys-
teresis. The SC2659 is ideal for implementing DC/DC
converters needed to power advanced microprocessors
such as Pentium
llI and Athlon
,
in both single and mul-
tiple processor configurations. Inhibit, under-voltage lock-
out and soft-start functions are included for controlled
power-up.
SC2659 features include an integrated 5 bit D/A con-
verter, temperature compensated voltage reference,
current limit comparator, over-current protection, and an
adaptive deadtime circuit to prevent shoot-through of
the power MOSFET during switching transitions. Power
good signaling, logic compatible shutdown, and over-volt-
age protection are also provided. The integrated D/A
converter provides programmability of output voltage
from 1.050V to 1.825V in 25mV increments.
The SC2659 high side driver can be configured as either
a ground-referenced or as a floating bootstrap driver.
The high and low side MOSFET drivers have a peak cur-
rent rating of 2 amps.
Typical Application Circuit
Server Systems and Workstations
Pentium
III Core Supplies
AMD Athlon
Core Supplies
Multiple Microprocessor Supplies
Voltage Regulator Modules
Programmable hysteresis
5 bit DAC programmable output (1.050V-1.825V)
On-chip power good and OVP functions
Designed to meet latest Intel specifications
Up to 95% efficiency
VIDs pulled up to +3.3V
R12
1.0
R14
1.6
L2
1.0uH
R3
*
R1
*
R4
1k
R2
1k
R5
*
R6
20k
R7
*
R8
10k
C5
C10
+12V
C8
0.033
R10
1k
+5V
R9
10k
+5V
C7
0.1
C1
0.1
Cin
Bulk
L1
0.5uH
PWRGD
INHIB
"POWER GOOD"
"INHIBIT"
+
_
Vin +5V/12V
1.05 to 1.825V
+
_
C9
1.0
Q1
FDB6035AL
Q2
FDB7030BL
Cout
Bulk
C4
0.01
R11
1k
C6
0.1
Cin
HF
Cout
HF
C2
0.001
C3
0.1
IOUT
1
DROOP
2
OCP
3
VHYST
4
VREFB
5
VSENSE
6
AGND
7
SOFTST
8
N/C
9
LODRV
10
LOHIB
11
DRVGND
12
LOWDR
13
DRV
14
VIN12V
15
BOOT
16
HIGHDR
17
BOOTLO
18
HISENSE
19
LOSENSE
20
IOUTLO
21
INHIBIT
22
VID25
23
VID3
24
VID2
25
VID1
26
VID0
27
PWRGD
28
U1
SC2659
*) for the values see specific application circuit somewhere else in the datasheet