SC2655 Datasheet, PDF (1/20 Pages) Semtech Corporation – Programmable Synchronous DC/DC Hysteretic Controller with VRM 9.0 VID Range

SC2655
Programmable Synchronous DC/DC
Hysteretic Controller with VRM 9.0 VID Range
POWER MANAGEMENT
Description
Features
The SC2655 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 SC2655 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.
SC2655 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 1.1V to 1.85V in 25mV increments.
‹ Programmable hysteresis
‹ 5 bit DAC programmable output (1.1V-1.85V)
‹ On-chip power good and OVP functions
‹ Designed to meet latest Intel specifications
‹ Up to 95% efficiency
‹ VIDs pulled up to +3.3V
Applications
‹ Server Systems and Workstations
‹ Pentium^® III Core Supplies
‹ AMD Athlon^® Core Supplies
‹ Multiple Microprocessor Supplies
‹ Voltage Regulator Modules
The SC2655 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
+5V
R2
1k
R4
1k
R5
*
R6
20k
C2
0.001
R1
*
R9
U1
10k
SC2655
R3
*
1 _IOUT
PWRGD ²⁸
2 _DROOP
VID0 ²⁷
3 _OCP
VID1 ²⁶
4 _VHYST
VID2 ²⁵
5 _VREFB
C1
0.1
6 _VSENSE
VID3 ²⁴
VID4 ²³
7 _AGND
INHIBIT ²²
R10
1k
R11
1k
PWRGD
"POWER GOOD"
C6
0.1
INHIB
"INHIBIT"
C7
0.1
L1
0.5uH
Cin
HF
Cin
Bulk
8 _SOFTST
IOUTLO ²¹
C3
+5V
0.1
9 _N/C
LOSENSE ²⁰
C8
0.033
C4
0.01
10 _LODRV
11 _LOHIB
12 _DRVGND
HISENSE ¹⁹
BOOTLO ¹⁸
HIGHDR ¹⁷
Q1
FDB6035AL
R12
1.0
13 _LOWDR
14 _DRV
C5
BOOT ¹⁶
L2
1.0uH
+12V
C9
1.0
VIN12V ¹⁵
Q2
FDB7030BL
R14
1.6
Cout
Cout
Bulk
HF
C10
+
Vin +5V/12V
_
+
1.10 to 1.825V
_
R7
R8 *
10k
*) for the values see specific application circuit somewhere else in the datasheet
Revision: December 10, 2003
1
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