Datasheet

7
LTC1703
1703fa
OVERVIEW
The LTC1703 is a dual, step-down (buck), voltage mode
feedback switching regulator controller. It is designed to
be used in a synchronous switching architecture with two
external N-channel MOSFETs per channel. It is intended to
operate from a low voltage input supply (7V maximum)
and provide a high power, high efficiency, precisely regu-
lated output voltage. Several features make it particularly
suited for microprocessor supply regulation. Output regu-
lation is extremely tight, with DC line and load regulation
and initial accuracy better than 1.5%, and total regulation
including transient response inside of 3.5% with a prop-
BURST
LOGIC
SOFT
START
90% DUTY CYCLE
RUN/SS1,2
COMP1,2
10µA
4µA
500mV
800mV 760mV 840mV
I
MAX1,2
DRIVE
LOGIC
OSC
550kHz
+
–
I
LIM
FB
MIN MAX
920mV
FLT
0V
DIS
FCB
FB1,2
1703 BD
BOOST1,2
TG1,2
FROM
OTHER
CONTROLLER
SHUTDOWN TO
THIS CONTROLLER
SHUTDOWN TO
ENTIRE CHIP
FAULT
PV
CC
25µs
DELAY
FROM
OTHER
CONTROLLER
V
CC
SW1,2
BG1,2
PGND
SGND
10µA
40k
VID0
V
CC
40k
VID1
V
CC
40k
VID2
V
CC
40k
VID3
V
CC
40k
VID4
V
CC
R11
10k
R
B1
SENSE
TO FB1
SWITCH
CONTROL
LOGIC
erly designed circuit. The 550kHz switching frequency
allows the use of physically small, low value external
components without compromising performance. An
onboard DAC sets the output voltage at channel 1, consis-
tent with the Intel mobile VID specification (Table 1).
The LTC1703’s internal feedback amplifier is a 25MHz
gain-bandwidth op amp, allowing the use of complex
multipole/zero compensation networks. This allows the
feedback loop to maintain acceptable phase margin at
higher frequencies than traditional switching regulator
controllers allow, improving stability and maximizing tran-
sient response. The 800mV internal reference allows
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APPLICATIO S I FOR ATIO
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