LTC1736 Datasheet, PDF (1/28 Pages) Linear Technology – 5-Bit Adjustable High Efficiency Synchronous Step-Down Switching Regulator

LTC1736
5-Bit Adjustable
High Efficiency Synchronous
Step-Down Switching Regulator
FEATURES
s _{Dual N-Channel MOSFET Synchronous Drive}
s _{Synchronizable/Programmable Fixed Frequency}
s _{Wide VIN Range: 3.5V to 36V Operation}
s _{5-Bit Digital-to-Analog VOUT Selection:}
0.925V to 2.00V Range with 50mV/25mV Steps
s _OPTI-LOOP^TM _{Compensation Minimizes COUT}
s _{±1% Output Voltage Accuracy}
s _{Power Good Output Voltage Monitor}
s _{Active Voltage Positioning Compatible}
s _{Output Overvoltage Crowbar Protection}
s _{Internal Current Foldback}
s _{Latched Short-Circuit Shutdown Timer}
with Defeat Option
s _{Forced Continuous Control Pin}
s _{Optional Programmable Soft-Start}
s _{Remote Output Voltage Sense}
s _{Available in 24-Lead SSOP Package}
U
APPLICATIO S
s _{Notebook and Palmtop Computers, PDAs}
s _{Power Supply for Mobile Pentium}^® _{II and}
Pentium III Processors
s _{Low Voltage Power Supplies}
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP and Burst Mode are trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
DESCRIPTIO
The LTC^®1736 is a synchronous step-down switching
regulator controller optimized for CPU power. The output
voltage is programmed by a 5-bit digital-to-analog con-
verter (DAC) that adjusts the output voltage from 0.925V
to 2.00V according to Intel mobile VID specifications. The
0.8V reference is compatible with future microprocessor
generations.
The operating frequency (synchronizable up to 500kHz) is
set by an external capacitor allowing maximum flexibility
in optimizing efficiency. The output voltage is monitored by
a power good window comparator that indicates when the
output is within 7.5% of its programmed value.
Protection features include: internal foldback current lim-
iting, output overvoltage crowbar and optional short-cir-
cuit shutdown. Soft-start is provided by an external capaci-
tor that can be used to properly sequence supplies. The
operating current level is user-programmable via an exter-
nal current sense resistor. Wide input supply range allows
operation from 3.5V to 30V (36V maximum).
Pin defeatable Burst Mode^TM operation provides high effi-
ciency at low load currents. OPTI-LOOP compensation
allows the transient response to be optimized over a wide
range of output capacitance and ESR values.
TYPICAL APPLICATIO
C_OSC
47pF
C_SS
0.1µF
R_C
C_C1
330pF
33k
C_C2
47pF
47pF
C_OSC
V_IN
TG
RUN/SS
SW
I_TH
LTC1736 _VIDVCC
PGOOD
VID4
VID3
VID2
VID1
VID0
SGND
INTV_CC
BOOST
BG
PGND
V_OSENSE SENSE ^– SENSE ⁺
1000pF
V_IN
5V TO 24V
M1
FDS6680A
D_B
CMDSH-3 _CB
0.22µF
+
4.7µF
M2
FDS6680A
×2
C_IN
22µF/50V
×2
CERAMIC
L1
1.2µH
R_SENSE
0.004Ω
D1
MBRS340T3
V_OUT
1.35V TO 1.60V
12A
+ C_OUT
180µF/4V
×4
C_OUT: PANASONIC EEFUEOG181R
C_IN: MARCON THCR70EIH226ZT
L1: PANASONIC ETQP6RZIR20HFA
R_SENSE: IRC LRF2010-01-R004J
1736 F01
Figure 1. High Efficiency Step-Down Converter
1