Datasheet LTC1773 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Synchronous Step-Down DC/DC Controller |
| Pages / Page | 20 / 1 — FEATURES. DESCRIPTIO. High Efficiency: Up to 95%. Constant Frequency … |
| File Format / Size | PDF / 300 Kb |
| Document Language | English |
FEATURES. DESCRIPTIO. High Efficiency: Up to 95%. Constant Frequency 550kHz Operation. VIN from 2.65V to 8.5V
Model Line for this Datasheet
Text Version of Document
LTC1773 Synchronous Step-Down DC/DC Controller
U FEATURES DESCRIPTIO
■
High Efficiency: Up to 95%
The LTC®1773 is a current mode synchronous buck regu- ■
Constant Frequency 550kHz Operation
lator controller that drives external complementary power ■
VIN from 2.65V to 8.5V
MOSFETs using a fixed frequency architecture. The oper- ■
VOUT from 0.8V to VIN
ating supply range is from 2.65V to 8.5V, making it ■
OPTI-LOOP
®
Compensation Minimizes COUT
suitable for 1- or 2-cell lithium-ion battery powered appli- ■
Synchronizable up to 750kHz
cations. Burst Mode® operation provides high efficiency at ■
Selectable Burst Mode Operation
low load currents. 100% duty cycle provides low dropout ■
Low Quiescent Current: 80
µ
A
operation which extends operating time in battery-oper- ■ Low Dropout Operation: 100% Duty Cycle ated systems. ■ Secondary Winding Regulation The operating frequency is internally set at 550kHz, allow- ■ Soft-Start ing the use of small surface mount inductors. For switch- ■ Current Mode Operation for Excellent Line and ing-noise sensitive applications, it can be synchronized up Load Transient Response to 750kHz. Peak current limit is user programmable with ■ Low Shutdown IQ = 10µA an external high side sense resistor. A SYNC/FCB control ■ ±1.5% Reference Accuracy pin guarantees regulation of secondary windings regard- ■ Precision 2.5V Undervoltage Lockout less of load on the main output by forcing continuous ■ Available in 10-Lead MSOP operation. Burst Mode operation is inhibited during syn-
U APPLICATIO S
chronization or when the SYNC/FCB pin is pulled low to reduce noise and RF interference. Soft-start is provided by ■ Cellular Telephones an external capacitor. ■ RF PA Supplies Synchronous rectification increases efficiency and elimi- ■ Portable Instruments nates the need for a Schottky diode, saving components ■ Wireless MODEMS and board space. The LTC1773 comes in a 10-lead MSOP ■ Distributed Power Systems package. ■ Notebook and Palm Top Computers, PDAs , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ■ Single and Dual Cell Lithium-Ion Powered Devices All other trademarks are the property of their respective owners. OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815.
U TYPICAL APPLICATIO
VIN 2.65V TO 8.5V
High Efficiency
100 + 95 VIN = 3.3V SYNC/FCB V R C IN SENSE IN 0.025Ω 68µF 90 VIN = 5V RUN/SS SENSE– 85 0.1µF L1 VIN = 8V ITH TG 3µH 80 V 47pF LTC1773 OUT 30k 2.5V SW 75 220pF EFFICIENCY (%) 70 VFB BG GND 65 Si9801DY + COUT 180µF 60 L = SUMIDA CDRH6D28-3R0 80.6k 55 169k 1 10 100 1000 5000 1773 F01 OUTPUT CURRENT (mA)
Figure 1. Step-Down Converter
1773 F1b 1773fb 1
U FEATURES DESCRIPTIO
■
High Efficiency: Up to 95%
The LTC®1773 is a current mode synchronous buck regu- ■
Constant Frequency 550kHz Operation
lator controller that drives external complementary power ■
VIN from 2.65V to 8.5V
MOSFETs using a fixed frequency architecture. The oper- ■
VOUT from 0.8V to VIN
ating supply range is from 2.65V to 8.5V, making it ■
OPTI-LOOP
®
Compensation Minimizes COUT
suitable for 1- or 2-cell lithium-ion battery powered appli- ■
Synchronizable up to 750kHz
cations. Burst Mode® operation provides high efficiency at ■
Selectable Burst Mode Operation
low load currents. 100% duty cycle provides low dropout ■
Low Quiescent Current: 80
µ
A
operation which extends operating time in battery-oper- ■ Low Dropout Operation: 100% Duty Cycle ated systems. ■ Secondary Winding Regulation The operating frequency is internally set at 550kHz, allow- ■ Soft-Start ing the use of small surface mount inductors. For switch- ■ Current Mode Operation for Excellent Line and ing-noise sensitive applications, it can be synchronized up Load Transient Response to 750kHz. Peak current limit is user programmable with ■ Low Shutdown IQ = 10µA an external high side sense resistor. A SYNC/FCB control ■ ±1.5% Reference Accuracy pin guarantees regulation of secondary windings regard- ■ Precision 2.5V Undervoltage Lockout less of load on the main output by forcing continuous ■ Available in 10-Lead MSOP operation. Burst Mode operation is inhibited during syn-
U APPLICATIO S
chronization or when the SYNC/FCB pin is pulled low to reduce noise and RF interference. Soft-start is provided by ■ Cellular Telephones an external capacitor. ■ RF PA Supplies Synchronous rectification increases efficiency and elimi- ■ Portable Instruments nates the need for a Schottky diode, saving components ■ Wireless MODEMS and board space. The LTC1773 comes in a 10-lead MSOP ■ Distributed Power Systems package. ■ Notebook and Palm Top Computers, PDAs , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ■ Single and Dual Cell Lithium-Ion Powered Devices All other trademarks are the property of their respective owners. OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815.
U TYPICAL APPLICATIO
VIN 2.65V TO 8.5V
High Efficiency
100 + 95 VIN = 3.3V SYNC/FCB V R C IN SENSE IN 0.025Ω 68µF 90 VIN = 5V RUN/SS SENSE– 85 0.1µF L1 VIN = 8V ITH TG 3µH 80 V 47pF LTC1773 OUT 30k 2.5V SW 75 220pF EFFICIENCY (%) 70 VFB BG GND 65 Si9801DY + COUT 180µF 60 L = SUMIDA CDRH6D28-3R0 80.6k 55 169k 1 10 100 1000 5000 1773 F01 OUTPUT CURRENT (mA)
Figure 1. Step-Down Converter
1773 F1b 1773fb 1
