LTC3714
Intel Compatible,
Wide Operating Range, Step-Down Controller
with Internal Op Amp
DESCRIPTIO
The LTC
®
3714 is a synchronous step-down switching
regulator controller for CPU power. An output voltage
between 0.6V and 1.75V is selected by a 5-bit code (Intel
mobile VID specification). The controller uses a constant
on-time, valley current control architecture to deliver very
low duty cycles without requiring a sense resistor. Oper-
ating frequency is selected by an external resistor and is
compensated for variations in V
IN
and V
OUT
.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
when the main output is lightly loaded. Internal op amp
allows programmable offsets to the output voltage during
power saving modes.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit level is user pro-
grammable. Wide supply range allows operation from 4V
to 36V at the input.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
FEATURES
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True Current Mode with Ultrafast Transient
Response
Stable with Ceramic C
OUT
t
ON(MIN)
< 100ns for Operation from High Input
Ranges
Supports Active Voltage Positioning
No Sense Resistor Required
5-Bit VID Programmable Output Voltage: 0.6V to 1.75V
Dual N-Channel MOSFET Synchronous Drive
Programmable Output Offsets
Power Good Output Voltage Monitor
Wide V
IN
Range: 4V to 36V
±1%
0.6V Reference
Adjustable Frequency
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
Forced Continuous Control Pin
Logic Controlled Micropower Shutdown: I
Q
≤
30µA
Available in 0.209" Wide 28-Lead SSOP Package
APPLICATIO S
s
s
Power Supply for Mobile Pentium
®
Processors and
Transmeta Processors
Notebook and Portable Computers
TYPICAL APPLICATIO
LTC3714
INTV
CC
C
SS
0.1µF
PGOOD
I
ON
V
IN
RUN/SS
I
TH
C
C
R
C
SGND
INTV
CC
VID4
VID3
5-BIT
VID
VID2
VID1
VID0
PGND
V
OSENSE
*OPTIONAL
BG
SENSE
TG
SW
BOOST
C
B
, 0.22µF
D
B
CMDSH-3
R
ON
Transient Response of 8A to 23A Output Load Step
M1
IRF7811 L1
×2
0.68µH
10µF
35V
×4
V
IN
5V TO 24V
+
M2
IRF7811
×3
D1*
UPS840
C
OUT
270µF
2V
×4
V
OUT
0.6V TO 1.75V
23A
+
C
VCC
4.7µF
0.003Ω*
3714 F01
Figure 1. High Efficiency Step-Down Converter
U
U
U
1.395V
V
OUT
(1.35V)
50mV/DIV
1.213V
23A
I
LOAD
10A/DIV
8A
20µs/DIV
3714 TA03
3714f
1