Datasheet LTC1775 (Analog Devices)
| Fabricante | Analog Devices |
| Descripción | High Power No RSENSE Current Mode Synchronous Step-Down Switching Regulator |
| Páginas / Página | 24 / 1 — FEATURES. DESCRIPTIO. Highest Efficiency Current Mode Controller. No … |
| Formato / tamaño de archivo | PDF / 307 Kb |
| Idioma del documento | Inglés |
FEATURES. DESCRIPTIO. Highest Efficiency Current Mode Controller. No Sense Resistor Required
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LTC1775 High Power No R TM SENSE Current Mode Synchronous Step-Down Switching Regulator
U FEATURES DESCRIPTIO
■
Highest Efficiency Current Mode Controller
The LTC®1775 is a synchronous step-down switching ■
No Sense Resistor Required
regulator controller that drives external N-channel power ■
300mV Maximum Current Sense Voltage
MOSFETs using few external components. Current mode ■
Stable High Current Operation
control with MOSFET VDS sensing eliminates the need for ■
Dual N-Channel MOSFET Synchronous Drive
a sense resistor and improves efficiency. Largely similar ■ Wide VIN Range: 4V to 36V to the LTC1625, the LTC1775 has twice the maximum ■
Wide VOUT Range: 1.19V to VIN
sense voltage for high current applications. The frequency ■ ±1% 1.19V Reference of a nominal 150kHz internal oscillator can be synchro- ■ Programmable Fixed Frequency with Injection Lock nized to an external clock over a 1.5:1 frequency range. ■ Very Low Drop Out Operation: 99% Duty Cycle Burst ModeTM operation at low load currents reduces ■ Forced Continuous Mode Control Pin switching losses and low dropout operation extends oper- ■ Optional Programmable Soft Start ating time in battery-powered systems. A forced continu- ■ Pin Selectable Output Voltage ous mode control pin can assist secondary winding ■ Foldback Current Limit regulation by disabling Burst Mode operation when the ■ Output Overvoltage Protection main output is lightly loaded. ■ Logic Controlled Micropower Shutdown: IQ < 30µA ■ Available in 16-Lead Narrow SSOP and SO Packages Fault protection is provided by foldback current limiting
U
and an output overvoltage comparator. An external ca-
APPLICATIO S
pacitor attached to the RUN/SS pin provides soft start capability for supply sequencing. A wide supply range ■ Notebook Computers allows operation from 4V (4.3V for LTC1775I) to 36V at the ■ Automotive Electronics input and 1.19V to VIN at the output. ■ Battery Chargers , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Distributed Power Systems No RSENSE and Burst Mode are trademarks of Linear Technology Corporation.
U TYPICAL APPLICATION Efficiency vs Load Current
LTC1775 100 VIN VIN = 10V SYNC VIN 5V TO f = 150kHz V + C OUT = 5V IN TK 28V CSS 0.1µF 22µF 95 FCB = INTVCC M1 RUN/SS TG 30V SUD50N03-10 L1 ×4 90 6µH VOUT = 3.3V V SW V PROG OUT CB 0.33µF 3.3V BOOST + 10A 85 R COUT C D D1 B 10k 680µF CMDSH-3 MBRS340 6.3V C I INTV TH CC EFFICIENCY (%) C 80 2.2nF M2 SGND BG SUD50N03-10 + CVCC 75 4.7µF VOSENSE PGND 70 1775 F01 0.01 0.1 1 10 LOAD CURRENT (A)
Figure 1. High Efficiency Step-Down Converter
1775 F01b 1
U FEATURES DESCRIPTIO
■
Highest Efficiency Current Mode Controller
The LTC®1775 is a synchronous step-down switching ■
No Sense Resistor Required
regulator controller that drives external N-channel power ■
300mV Maximum Current Sense Voltage
MOSFETs using few external components. Current mode ■
Stable High Current Operation
control with MOSFET VDS sensing eliminates the need for ■
Dual N-Channel MOSFET Synchronous Drive
a sense resistor and improves efficiency. Largely similar ■ Wide VIN Range: 4V to 36V to the LTC1625, the LTC1775 has twice the maximum ■
Wide VOUT Range: 1.19V to VIN
sense voltage for high current applications. The frequency ■ ±1% 1.19V Reference of a nominal 150kHz internal oscillator can be synchro- ■ Programmable Fixed Frequency with Injection Lock nized to an external clock over a 1.5:1 frequency range. ■ Very Low Drop Out Operation: 99% Duty Cycle Burst ModeTM operation at low load currents reduces ■ Forced Continuous Mode Control Pin switching losses and low dropout operation extends oper- ■ Optional Programmable Soft Start ating time in battery-powered systems. A forced continu- ■ Pin Selectable Output Voltage ous mode control pin can assist secondary winding ■ Foldback Current Limit regulation by disabling Burst Mode operation when the ■ Output Overvoltage Protection main output is lightly loaded. ■ Logic Controlled Micropower Shutdown: IQ < 30µA ■ Available in 16-Lead Narrow SSOP and SO Packages Fault protection is provided by foldback current limiting
U
and an output overvoltage comparator. An external ca-
APPLICATIO S
pacitor attached to the RUN/SS pin provides soft start capability for supply sequencing. A wide supply range ■ Notebook Computers allows operation from 4V (4.3V for LTC1775I) to 36V at the ■ Automotive Electronics input and 1.19V to VIN at the output. ■ Battery Chargers , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Distributed Power Systems No RSENSE and Burst Mode are trademarks of Linear Technology Corporation.
U TYPICAL APPLICATION Efficiency vs Load Current
LTC1775 100 VIN VIN = 10V SYNC VIN 5V TO f = 150kHz V + C OUT = 5V IN TK 28V CSS 0.1µF 22µF 95 FCB = INTVCC M1 RUN/SS TG 30V SUD50N03-10 L1 ×4 90 6µH VOUT = 3.3V V SW V PROG OUT CB 0.33µF 3.3V BOOST + 10A 85 R COUT C D D1 B 10k 680µF CMDSH-3 MBRS340 6.3V C I INTV TH CC EFFICIENCY (%) C 80 2.2nF M2 SGND BG SUD50N03-10 + CVCC 75 4.7µF VOSENSE PGND 70 1775 F01 0.01 0.1 1 10 LOAD CURRENT (A)
Figure 1. High Efficiency Step-Down Converter
1775 F01b 1