Datasheet LTC3549 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | 250mA Low VIN Buck Regulator in 2mm × 3mm DFN |
| Pages / Page | 16 / 1 — FEATURES. DESCRIPTIO. 1.6V to 5.5V Input Voltage Range. Internal … |
| File Format / Size | PDF / 370 Kb |
| Document Language | English |
FEATURES. DESCRIPTIO. 1.6V to 5.5V Input Voltage Range. Internal Soft-Start. Low Ripple Burst Mode. Operation
Model Line for this Datasheet
Text Version of Document
LTC3549 250mA Low VIN Buck Regulator in 2mm × 3mm DFN
U FEATURES DESCRIPTIO
■
1.6V to 5.5V Input Voltage Range
The LTC®3549 is a high effi ciency, monolithic synchronous ■
Internal Soft-Start
buck regulator using a constant-frequency, current mode ■
Low Ripple Burst Mode
®
Operation
architecture. The output voltage is adjusted via an external
Output Ripple: <20mV
resistor divider.
P-P IQ: 50µA
A fi xed switching frequency of 2.25MHz is supported. ■
2.25MHz Constant-Frequency Operation
This switching frequency allows the use of small surface ■ High Effi ciency: Up to 93% mount inductors and capacitors, including ceramics. ■ 250mA Output Current (VIN = 1.8V, VOUT = 1.2V) ■ 450mA Peak Inductor Current Supply current during Burst Mode operation is only 50µA ■ No Schottky Diode Required dropping to < 1µA in shutdown. The 1.6V to 5.5V input ■ Low Dropout Operation: 100% Duty Cycle voltage range makes the LTC3549 ideally suited for single ■ 0.611V Reference Voltage cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH ■ Stable with Ceramic Capacitors battery-powered applications. 100% duty cycle capabil- ■ Shutdown Mode Draws <1µA Supply Current ity provides low dropout operation, extending battery ■ Current Mode Operation for Excellent Line and Load life in portable systems. Burst Mode operation can be Transient Response user-enabled, increasing effi ciency at light loads, further ■ Overtemperature Protection extending battery life. ■ Available in a Low Profi le (0.75mm) 6-Lead The internal synchronous switch increases effi ciency and (2mm x 3mm) DFN Package eliminates the need for an external Schottky diode. Internal soft-start offers controlled output voltage rise time at start-
U
up without the need for external components.
APPLICATIO S
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ■ 2 AA-Cell Applications Burst Mode is a registered trademark of Linear Technology Corporation. All other ■ Cellular Phones trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. ■ Digital Cameras ■ MP3 Players
U TYPICAL APPLICATIO Burst Mode Effi ciency, VOUT = 1.5V
100 1
High Effi ciency Step-Down Converter
90 80 0.1 LTC3549 3.3µH* 70 POWER LOSS (W) V SW OUT VIN V 1.5V IN 22pF 60 1.8V TO 4.7µF 4.7µF 5.5V RUN 50 0.01 CER CER MODE VFB 40 200k EFFICIENCY (%) 137k 30 VIN = 1.8V 0.001 GND V 20 IN = 2.5V VIN = 3.1V 10 POWER LOST *TDK VLF3012AT-3R3MR87 3549 TA01 AT VIN = 2.5V 0 0.0001 0.1 1 10 100 1k LOAD CURRENT (mA) 3549 TA02 3549f 1
U FEATURES DESCRIPTIO
■
1.6V to 5.5V Input Voltage Range
The LTC®3549 is a high effi ciency, monolithic synchronous ■
Internal Soft-Start
buck regulator using a constant-frequency, current mode ■
Low Ripple Burst Mode
®
Operation
architecture. The output voltage is adjusted via an external
Output Ripple: <20mV
resistor divider.
P-P IQ: 50µA
A fi xed switching frequency of 2.25MHz is supported. ■
2.25MHz Constant-Frequency Operation
This switching frequency allows the use of small surface ■ High Effi ciency: Up to 93% mount inductors and capacitors, including ceramics. ■ 250mA Output Current (VIN = 1.8V, VOUT = 1.2V) ■ 450mA Peak Inductor Current Supply current during Burst Mode operation is only 50µA ■ No Schottky Diode Required dropping to < 1µA in shutdown. The 1.6V to 5.5V input ■ Low Dropout Operation: 100% Duty Cycle voltage range makes the LTC3549 ideally suited for single ■ 0.611V Reference Voltage cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH ■ Stable with Ceramic Capacitors battery-powered applications. 100% duty cycle capabil- ■ Shutdown Mode Draws <1µA Supply Current ity provides low dropout operation, extending battery ■ Current Mode Operation for Excellent Line and Load life in portable systems. Burst Mode operation can be Transient Response user-enabled, increasing effi ciency at light loads, further ■ Overtemperature Protection extending battery life. ■ Available in a Low Profi le (0.75mm) 6-Lead The internal synchronous switch increases effi ciency and (2mm x 3mm) DFN Package eliminates the need for an external Schottky diode. Internal soft-start offers controlled output voltage rise time at start-
U
up without the need for external components.
APPLICATIO S
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ■ 2 AA-Cell Applications Burst Mode is a registered trademark of Linear Technology Corporation. All other ■ Cellular Phones trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. ■ Digital Cameras ■ MP3 Players
U TYPICAL APPLICATIO Burst Mode Effi ciency, VOUT = 1.5V
100 1
High Effi ciency Step-Down Converter
90 80 0.1 LTC3549 3.3µH* 70 POWER LOSS (W) V SW OUT VIN V 1.5V IN 22pF 60 1.8V TO 4.7µF 4.7µF 5.5V RUN 50 0.01 CER CER MODE VFB 40 200k EFFICIENCY (%) 137k 30 VIN = 1.8V 0.001 GND V 20 IN = 2.5V VIN = 3.1V 10 POWER LOST *TDK VLF3012AT-3R3MR87 3549 TA01 AT VIN = 2.5V 0 0.0001 0.1 1 10 100 1k LOAD CURRENT (mA) 3549 TA02 3549f 1
