Datasheet LTC1735-1 (Analog Devices)

ManufacturerAnalog Devices
DescriptionHigh Efficiency Synchronous Step-Down Switching Regulator
Pages / Page28 / 1 — FEATURES. DESCRIPTIO. Programmable/Synchronizable Fixed Frequency. …
File Format / SizePDF / 356 Kb
Document Languageenglish

FEATURES. DESCRIPTIO. Programmable/Synchronizable Fixed Frequency. OPTI-LOOPTM Compensation Minimizes COUT

Datasheet LTC1735-1 Analog Devices

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LTC1735-1 High Efficiency Synchronous Step-Down Switching Regulator
U FEATURES DESCRIPTIO
■ Dual N-Channel MOSFET Synchronous Drive The LTC®1735-1 is a synchronous step-down switching ■
Programmable/Synchronizable Fixed Frequency
regulator controller optimized for CPU power. OPTI-LOOP ■ V compensation allows the transient response to be opti- OUT Range: 0.8V to 7V ■ Wide V mized over a wide range of output capacitance and ESR IN Range: 3.5V to 36V Operation ■ Very Low Dropout Operation: 99% Duty Cycle values. ■
OPTI-LOOPTM Compensation Minimizes COUT
The operating frequency (synchronizable up to 500kHz) is ■ ±
1% Output Voltage Accuracy
set by an external capacitor allowing maximum flexibility ■
Power Good Output Voltage Monitor
in optimizing efficiency. The output voltage is monitored ■ Internal Current Foldback by a power good window comparator that indicates when ■ Output Overvoltage Crowbar Protection the output is within 7.5% of its programmed value, con- ■ Latched Short-Circuit Shutdown Timer forming to Intel Mobile CPU Specifications. with Defeat Option ■ Optional Programmable Soft-Start Protection features include internal foldback current lim- ■ Remote Output Voltage Sense iting, output overvoltage crowbar and optional short- ■ Logic Controlled Micropower Shutdown: I circuit shutdown. Soft-start is provided by an external Q < 25µA ■ Available in 16-Lead Narrow SSOP and SO Packages capacitor that can be used to properly sequence supplies.
U
The operating current level is user-programmable via an
APPLICATIO S
external current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum). ■ Notebook and Palmtop Computers, PDAs ■ Power Supply for Mobile Pentium® III Processor with Pin defeatable Burst ModeTM operation provides high SpeedStepTM Technology efficiency at low load currents while 99% duty cycle ■ Cellular Telephones and Wireless Modems provides low dropout operation. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation. Pentium is a registered trademark of Intel Corporation. SpeedStep is a trademark of Intel Corporation.
U TYPICAL APPLICATIO
VIN PGOOD 4.5V TO 24V C C IN IN: MARCON THCR70E1H226ZT 22µF COUT: PANASONIC EEFUE06181R C 50V L1: PANASONIC ETQP6RZ1R20HFA OSC 47pF 1 16 Q1 COSC TG CERAMIC RSENSE: IRC CRF2010-01-R004J FDS6680A CSS 0.1µF 2 15 CB 0.22µF ×2 RUN/SS BOOST L1 C R R C2 330pF C1 33k 3 14 SENSE I 1.2µH TH LTC1735-1 SW 0.004Ω VOUT CC1 47pF 4 13 D1 1.35V TO 1.60V PGOOD VIN CMDSH-3 12A 5 12 D2 R1 SENSE – INTVCC MBRS340T3 10k 1000pF + 6 11 47pF C 47pF SENSE + BG OUT 4.7µF Q2, Q3 0.5% + 180µF 7 10 FDS6680A V R3 4V OSENSE PGND ×2 8 9 47pF 33.2k PANASONIC SP SGND EXTVCC 5V 1% ×4 (OPTIONAL) Q4 2N7002 VSEL = 1: VOUT = 1.60V 10Ω R2 VSEL = 0: VOUT = 1.35V 14.3k 10Ω 0.5% GND 1735-1 F01
Figure 1. CPU Core DC/DC Converter with Dynamic Voltage Selection from SpeedStep Enabled Processors
1
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