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LTC1439CGW Datasheet(PDF) 1 Page - Linear Technology |
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LTC1439CGW Datasheet(HTML) 1 Page - Linear Technology |
1 / 32 page 1 LTC1438/LTC1439 Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators Figure 1. High Efficiency Dual 5V/3V Step-Down Converter s Maintains Constant Frequency at Low Output Currents s Dual N-Channel MOSFET Synchronous Drive s Programmable Fixed Frequency (PLL Lockable) s Wide VIN Range: 3.5V to 36V Operation s Ultrahigh Efficiency s Very Low Dropout Operation: 99% Duty Cycle s Low Dropout, 0.5A Linear Regulator for VPP Generation or Low Noise Audio Supply s Built-In Power-On Reset Timer s Programmable Soft Start s Low-Battery Detector s Remote Output Voltage Sense s Foldback Current Limiting (Optional) s Pin Selectable Output Voltage s Logic-Controlled Micropower Shutdown: IQ < 30µA s Output Voltages from 1.19V to 9V s Available in 28- and 36-Lead SSOP Packages The LTC ®1438/LTC1439 are dual, synchronous step- down switching regulator controllers which drive external N-channel power MOSFETs in a phase-lockable fixed frequency architecture. The Adaptive Power TM output stage selectively drives two N-channel MOSFETs at frequencies up to 400kHz while reducing switching losses to maintain high efficiencies at low output currents. An auxiliary 0.5A linear regulator using an external PNP pass device provides a low noise, low dropout voltage source. A secondary winding feedback control pin (SFB1) guarantees regulation regardless of load on the main output by forcing continuous operation. An additional comparator is available for use as a low battery detector. A power-on reset timer (POR) is included which generates a signal delayed by 65536/fCLK (typ 300ms) after the output is within 5% of the regulated output voltage. Internal resistive dividers provide pin selectable output voltages with remote sense capability on one of the two outputs. The operating current levels are user-programmable via external current sense resistors. Wide input supply range allows operation from 3.5V to 30V (36V maximum). FEATURES DESCRIPTION , LTC and LT are registered trademarks of Linear Technology Corporation. Adaptive Power is a trademark of Linear Technology Corporation. TYPICAL APPLICATION BOOST 2 BOOST 1 TGL2 TGS2 SW2 BG2 SENSE+ 2 SENSE– 2 VOSENSE2 ITH2 TGL1 M3* M1 M2 TGS1 D1 MBR140T3 VOUT1 5V 3.5A VOUT2 3.3V 3.5A L1 10 µH SW1 BG1 LTC1439 SENSE+ 1 SENSE– 1 CSS1 0.1 µF CC1 1000pF COUT1 220 µF 10V RSENSE1 0.03 Ω RSENSE2 0.03 Ω COUT 220 µF 10V RC1 10k ITH1 RUN/SS2 PGND SGND VPROG2 CDSC INTVCC DB2, CMDSH-3 DB1, CMDSH-3 VIN VPROG1 RUN/SS1 D2 MBR140T3 CB1 0.1 µF CB2, 0.1µF 4.7 µF 16V M6* 1438 F01 M4 1000pF 1000pF COSC 56pF CSS2 0.1 µF CC1A 220pF M1, M2, M4, M5: Si4412DY M3, M6: IRLML2803 *NOT REQUIRED FOR LTC1438 CC2A 470pF CC2 1000pF RC2 10k + L2 10 µH VIN 5.2V TO 28V + + CIN 22 µF 35V × 4 + BOLD LINES INDICATE HIGH CURRENT PATHS M5 s Notebook and Palmtop Computers, PDAs s Portable Instruments s Battery-Operated Devices s DC Power Distribution Systems APPLICATIONS |
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