PROGRAMMABLE SYNCHRONOUS
DC/DC HYSTERETIC CONTROLLER
WITH VRM 9.0 VID RANGE
PRELIMINARY - August 7, 2000
SC1155
DESCRIPTION
The SC1155 is a synchronous-buck switch-mode con-
troller designed for use in single ended power supply
applications where efficiency is the primary concern.
The controller is a hysteretic type, with a user se-
lectable hysteresis. The SC1155 is ideal for implement-
ing DC/DC converters needed to power advanced mi-
croprocessors such as Pentium
廬
llI and Athlon
廬
, in both
single and multiple processor configurations. Inhibit,
under-voltage lockout and soft-start functions are in-
cluded for controlled power-up.
SC1155 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-voltage protection are also provided. The inte-
grated D/A converter provides programmability of out-
put voltage from 1.1V to 1.85V in 25mV increments.
The SC1155 high side driver can be configured as
either a grounded reference or as a floating bootstrap
driver. The high and low side MOSFET drivers have a
peak current rating of 2 amps.
FEATURES
鈥?
Programmable hysteresis
鈥?
5 bit DAC programmable output (1.1V-1.85V)
鈥?
On-chip power good and OVP functions
鈥?
Designed to meet latest Intel specifications
鈥?
Up to 95% efficiency
鈥?
+1% voltage tolerance over temperature
APPLICATIONS
鈥?
Server Systems and Workstations
鈥?
Intel Pentium
廬
III Core Supplies
鈥?
AMD Athlon
廬
Core Supplies
鈥?
Multiple Microprocessor Supplies
鈥?
Voltage Regulator Modules
ORDERING INFORMATION
DEVICE
(1)
PACKAGE
SO-28
TEMP. RANGE (T
J
)
0 - 125擄C
SC1155CSW.TR
SC1155EVB
Evaluation Board
TYPICAL APPLICATION CIRCUIT
Note:
(1) Only available in tape and reel packaging. A reel
contains 1000 devices.
U1
SC1155CSW
1
R1
2k
R3
2.7k
2
3
R2
1k
C2
0.01
R4
1k
C3
0.01
R5
100
C4
0.01
R6
20k
C6
0.1
4
5
6
7
C5
0.001
8
C7
0.1
C8
0.01
+5V
9
10
11
12
13
14
IOUT
DROOP
OCP
VHYST
VREFB
VSENSE
AGND
SOFTST
N/C
LODRV
LOHIB
DRVGND
LOWDR
DRV
PWRGD
VID0
VID1
VID2
VID3
VID4
INHIBIT
IOUTLO
LOSENSE
HISENSE
BOOTLO
HIGHDR
BOOT
VIN12V
28
27
26
25
24
23
22
21
20
19
18
17
16
+12V
15
Q2
R12 IRL2203S
3.9
C9
2.2uF
GND
R7
150
C21-C26
150uF/4V
C27
0.1
Q1
R11 IRL3103S
2.2
C13
0.33
L2
1.5uH
Vout
C12
0.33
GND
C16
0.1
L1
1uH
Vin
C17-C19
150uF/16V
C20
0.1
R10
10k
INHIB
R9
10k
+5V
PWRGD
Vin +5 to +12V
R8
10k
Vout = 1.1 to 1.85V
C8
2.2uF
Athlon is a registered trademark of AMD Corporation
Pentium is a registered trademark of Intel Corporation
1
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