Datasheet LTC1877 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | High Efficiency Monolithic Synchronous Step-Down Regulator |
| Pages / Page | 18 / 1 — FEATURES. DESCRIPTION. High Effi ciency: Up to 95%. Very Low Quiescent … |
| File Format / Size | PDF / 246 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. High Effi ciency: Up to 95%. Very Low Quiescent Current: Only 10μA. During Operation
Model Line for this Datasheet
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LTC1877 High Effi ciency Monolithic Synchronous Step-Down Regulator
FEATURES DESCRIPTION
n
High Effi ciency: Up to 95%
The LTC®1877 s a high effi ciency monolithic synchronous n
Very Low Quiescent Current: Only 10μA
buck regulator using a constant-frequency, current mode
During Operation
architecture. Supply current during operation is only 10μA n
600mA Output Current at VIN = 5V
and drops to < 1μA in shutdown. The 2.65V to 10V input n
2.65V to 10V Input Voltage Range
voltage range makes the LTC1877 ideally suited for both n
550kHz Constant-Frequency Operation
single and dual Li-Ion battery-powered applications. 100% n
No Schottky Diode Required
duty cycle provides low dropout operation, extending bat- n
Low Dropout Operation: 100% Duty Cycle
tery life in portable systems. n Synchronizable from 400kHz to 700kHz Switching frequency is internally set at 550kHz, allowing n Selectable Burst Mode® Operation or the use of small surface mount inductors and capacitors. Pulse-Skipping Mode For noise sensitive applications the LTC1877 can be exter- n 0.8V Reference Allows Low Output Voltages nally synchronized from 400kHz to 700kHz. Burst Mode n Shutdown Mode Draws < 1μA Supply Current operation is inhibited during synchronization or when the n ±2% Output Voltage Accuracy SYNC/MODE pin is pulled low, preventing low frequency n Current Mode Control for Excellent Line and Load ripple from interfering with audio circuitry. Transient Response n Overcurrent and Overtemperature Protected The internal synchronous switch increases effi ciency n Available in 8-Lead MSOP Package and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.8V
APPLICATIONS
feedback reference voltage. The LTC1877 is available in a space saving 8-lead MSOP package. Lower input voltage n Cellular Telephones applications (less than 7V abs max) should refer to the n Wireless Modems LTC1878 data sheet. n Personal Information Appliances n Portable Instruments L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective n Distributed Power Systems owners. n Battery-Powered Equipment
TYPICAL APPLICATION Effi ciency vs Output Current
100
High Effi ciency Step-Down Converter
95 VIN = 3.6V 10μH* V 90 IN 7 5 V † 2.65V SYNC SW OUT 3.3V 85 VIN = 10V TO 10V 10μF** 6 20pF LTC1877 + CER VIN 80 V 47μF*** IN = 7.2V 1 RUN 75 887k V 2 3 IN = 5V I VFB TH GND 70 EFFICIENCY (%) 220pF 280k 65 4 60 VOUT = 3.3V *TOKO D62CB A920CY-100M 55 L = 10μH **TAIYO-YUDEN CERAMIC LMK325BJ106MN Burst Mode OPERATION 50 ***SANYO POSCAP 6TPA47M 0.1 1.0 10 100 1000 †VOUT CONNECTED TO VIN FOR 2.65V < VIN < 3.3V 1877 TA01 OUTPUT CURRENT (mA) 1877 TA02 1877fb 1
FEATURES DESCRIPTION
n
High Effi ciency: Up to 95%
The LTC®1877 s a high effi ciency monolithic synchronous n
Very Low Quiescent Current: Only 10μA
buck regulator using a constant-frequency, current mode
During Operation
architecture. Supply current during operation is only 10μA n
600mA Output Current at VIN = 5V
and drops to < 1μA in shutdown. The 2.65V to 10V input n
2.65V to 10V Input Voltage Range
voltage range makes the LTC1877 ideally suited for both n
550kHz Constant-Frequency Operation
single and dual Li-Ion battery-powered applications. 100% n
No Schottky Diode Required
duty cycle provides low dropout operation, extending bat- n
Low Dropout Operation: 100% Duty Cycle
tery life in portable systems. n Synchronizable from 400kHz to 700kHz Switching frequency is internally set at 550kHz, allowing n Selectable Burst Mode® Operation or the use of small surface mount inductors and capacitors. Pulse-Skipping Mode For noise sensitive applications the LTC1877 can be exter- n 0.8V Reference Allows Low Output Voltages nally synchronized from 400kHz to 700kHz. Burst Mode n Shutdown Mode Draws < 1μA Supply Current operation is inhibited during synchronization or when the n ±2% Output Voltage Accuracy SYNC/MODE pin is pulled low, preventing low frequency n Current Mode Control for Excellent Line and Load ripple from interfering with audio circuitry. Transient Response n Overcurrent and Overtemperature Protected The internal synchronous switch increases effi ciency n Available in 8-Lead MSOP Package and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.8V
APPLICATIONS
feedback reference voltage. The LTC1877 is available in a space saving 8-lead MSOP package. Lower input voltage n Cellular Telephones applications (less than 7V abs max) should refer to the n Wireless Modems LTC1878 data sheet. n Personal Information Appliances n Portable Instruments L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective n Distributed Power Systems owners. n Battery-Powered Equipment
TYPICAL APPLICATION Effi ciency vs Output Current
100
High Effi ciency Step-Down Converter
95 VIN = 3.6V 10μH* V 90 IN 7 5 V † 2.65V SYNC SW OUT 3.3V 85 VIN = 10V TO 10V 10μF** 6 20pF LTC1877 + CER VIN 80 V 47μF*** IN = 7.2V 1 RUN 75 887k V 2 3 IN = 5V I VFB TH GND 70 EFFICIENCY (%) 220pF 280k 65 4 60 VOUT = 3.3V *TOKO D62CB A920CY-100M 55 L = 10μH **TAIYO-YUDEN CERAMIC LMK325BJ106MN Burst Mode OPERATION 50 ***SANYO POSCAP 6TPA47M 0.1 1.0 10 100 1000 †VOUT CONNECTED TO VIN FOR 2.65V < VIN < 3.3V 1877 TA01 OUTPUT CURRENT (mA) 1877 TA02 1877fb 1
