Datasheet LTC1874 (Analog Devices)

ManufacturerAnalog Devices
DescriptionDual Constant Frequency Current Mode Step-Down DC/DC Controller
Pages / Page12 / 1 — FEATURES. DESCRIPTIO. High Efficiency: Up to 94%. High Output Currents …
File Format / SizePDF / 190 Kb
Document Languageenglish

FEATURES. DESCRIPTIO. High Efficiency: Up to 94%. High Output Currents Easily Achieved. Wide V. IN Range: 2.5V to 9.8V

Datasheet LTC1874 Analog Devices

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LTC1874 Dual Constant Frequency Current Mode Step-Down DC/DC Controller
U FEATURES DESCRIPTIO

High Efficiency: Up to 94%
The LTC®1874 is a dual constant frequency current mode ■
High Output Currents Easily Achieved
step-down DC/DC controller with excellent AC and DC load ■
Wide V
and line regulation. Each controller has an accurate
IN Range: 2.5V to 9.8V

Constant Frequency 550kHz Operation
undervoltage lockout that shuts down the individual con- ■
Burst ModeTM Operation at Light Load
troller when the input voltage falls below 2.0V. ■
Low Dropout: 100% Duty Cycle
The LTC1874 boasts ±2.5% output voltage accuracy and ■ 0.8V Reference Allows Low Output Voltages consumes only 270µA of quiescent current per controller. ■ Current Mode Operation for Excellent The LTC1874 is configured with Burst Mode operation, Line and Load Transient Response which enhances efficiency at low output current for appli- ■ Low Quiescent Current: 270µA (Each Controller) cations where efficiency is a prime consideration. ■ Separate Shutdown Pin for Each Controller ■ Shutdown Mode Draws Only To further maximize the life of a battery source, each 8 external P-channel MOSFET is turned on continuously in µA Supply Current (Each Controller) ■ dropout (100% duty cycle). In shutdown, each controller ±2.5% Reference Accuracy ■ Available in 16-Lead Narrow SSOP draws a mere 8µA. High constant operating frequency of ■
Each Controller Functions Independent of the Other
550kHz allows the use of small external inductors.
U
The LTC1874 is available in a small footprint 16-lead
APPLICATIO S
narrow SSOP. ■ 1- or 2-Cell Lithium-Ion-Powered Applications , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. ■ Personal Information Appliances ■ Portable Computers ■ Distributed 3.3V, 2.5V or 1.8V Power Systems
U TYPICAL APPLICATION
VIN 3.5V C TO 9.5V IN R1 R2 10µF LTC1874 0.04Ω 1 8 0.04Ω 16V VIN1 PVIN2 ×2 2 7 SENSE1– PGATE2 M2 L2 4.7µH 3 6 VOUT2 L1 M1 GND1 PGND2 1.8V V 4.7µH OUT1 4 5 10k + C2 1A 3.3V VFB1 ITH/RUN2 D2 47µF 1A + 10k C1 13 12 220pF 6V D1 ITH/RUN1 VFB2 47µF 220pF 14 11 C1, C2: SANYO POSCAP 6TPA47M 6V 249k PGND1 GND2 CIN: TAIYO YUDEN CERAMIC 15 10 EMK325BJ106MNT (× 2) PGATE1 SENSE2– 100k D1, D2: MBRM120 16 9 80.6k L1, L2: COILCRAFT D01608C-472 PVIN1 VIN2 M1, M2: Si3443DV 80.6k R1, R2: DALE 0.25W 1874 TA01
Figure 1. LTC1874 3.5V-9.5V Input to 3.3V/1A and 1.8V/1A Dual Step-Down Converter
1
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