Datasheet LTC1772B (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23 |
| Pages / Page | 16 / 1 — FEATURES. DESCRIPTION. Burst Mode® Operation Disabled for Lower Output. … |
| File Format / Size | PDF / 226 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Burst Mode® Operation Disabled for Lower Output. Ripple at Light Loads. High Effi ciency: Up to 94%
Model Line for this Datasheet
Text Version of Document
LTC1772B Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23
FEATURES DESCRIPTION
n
Burst Mode® Operation Disabled for Lower Output
The LTC®1772B is a constant frequency current mode
Ripple at Light Loads
step-down DC/DC controller providing excellent AC and n
High Effi ciency: Up to 94%
DC load and line regulation. The device incorporates an n
High Output Currents Easily Achieved
accurate undervoltage lockout feature that shuts down the n
Wide VIN Range: 2.5V to 9.8V
LTC1772B when the input voltage falls below 2.0V. n
Constant Frequency 550kHz Operation
The LTC1772B provides a ± 2.5% output voltage accuracy n
Low Dropout: 100% Duty Cycle
and consumes only 270μA of quiescent current. In shut- n Output Voltage Down to 0.8V down, the device draws a mere 8μA. n Current Mode Operation for Excellent Line and Load Transient Response To further maximize the life of a battery source, the n Shutdown Mode Draws Only 8µA Supply Current external P-channel MOSFET is turned on continuously n Tiny 6-Lead TSOT-23 Package in dropout (100% duty cycle). High constant operating frequency of 550kHz allows the use of a small external inductor.
APPLICATIONS
The LTC1772B is available in a small footprint 6-lead n One or Two Lithium-Ion-Powered Applications TSOT-23. n Cellular Telephones For a Burst Mode operation enabled version of the n Wireless Devices LTC1772B, please refer to the LTC1772 data sheet. n Portable Computers L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. n Distributed 3.3V, 2.5V or 1.8V Power Systems All other trademarks are the property of their respective owners.
TYPICAL APPLICATION Effi ciency vs Load Current*
VIN 100 2.5V LTC1772 R1 C1 TO 9.8V 95 Burst Mode 0.03Ω 10μF OPERATION 10V 90 1 6 L1 ITH/RUN PGATE M1 4.7μH V 85 OUT 10k LTC1772B 2.5V 2 5 + C2A C2B 2A 80 LTC1772B GND VIN D1 47μF 1μF NON-Burst Mode 220pF 3 4 6V 10V 174k OPERATION V 75 FB SENSE– EFFICIENCY (%) 70 C1: TAIYO YUDEN LMK325BJ106K-T 65 C2A: SANYO 6TPA47M V 80.6k IN = 3.6V C2B: AVX 0805ZC105KAT1A VOUT = 2.5V D1: MOTOROLA MBRM120T3 60 10 100 1000 10000 L1: MURATA LQN6C-4R7 M1: FAIRCHILD FDC638P LOAD CURRENT (mA) 1772 F01a R1: IRC LRC-LR1206-01-R030F *OUTPUT RIPPLE WAVEFORMS FOR THE CIRCUIT OF FIGURE 1 APPEAR IN FIGURE 2. 1772 F01b
Figure 1. High Effi ciency, High Output Current 2.5V/2A Regulator
1772bfa 1
FEATURES DESCRIPTION
n
Burst Mode® Operation Disabled for Lower Output
The LTC®1772B is a constant frequency current mode
Ripple at Light Loads
step-down DC/DC controller providing excellent AC and n
High Effi ciency: Up to 94%
DC load and line regulation. The device incorporates an n
High Output Currents Easily Achieved
accurate undervoltage lockout feature that shuts down the n
Wide VIN Range: 2.5V to 9.8V
LTC1772B when the input voltage falls below 2.0V. n
Constant Frequency 550kHz Operation
The LTC1772B provides a ± 2.5% output voltage accuracy n
Low Dropout: 100% Duty Cycle
and consumes only 270μA of quiescent current. In shut- n Output Voltage Down to 0.8V down, the device draws a mere 8μA. n Current Mode Operation for Excellent Line and Load Transient Response To further maximize the life of a battery source, the n Shutdown Mode Draws Only 8µA Supply Current external P-channel MOSFET is turned on continuously n Tiny 6-Lead TSOT-23 Package in dropout (100% duty cycle). High constant operating frequency of 550kHz allows the use of a small external inductor.
APPLICATIONS
The LTC1772B is available in a small footprint 6-lead n One or Two Lithium-Ion-Powered Applications TSOT-23. n Cellular Telephones For a Burst Mode operation enabled version of the n Wireless Devices LTC1772B, please refer to the LTC1772 data sheet. n Portable Computers L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. n Distributed 3.3V, 2.5V or 1.8V Power Systems All other trademarks are the property of their respective owners.
TYPICAL APPLICATION Effi ciency vs Load Current*
VIN 100 2.5V LTC1772 R1 C1 TO 9.8V 95 Burst Mode 0.03Ω 10μF OPERATION 10V 90 1 6 L1 ITH/RUN PGATE M1 4.7μH V 85 OUT 10k LTC1772B 2.5V 2 5 + C2A C2B 2A 80 LTC1772B GND VIN D1 47μF 1μF NON-Burst Mode 220pF 3 4 6V 10V 174k OPERATION V 75 FB SENSE– EFFICIENCY (%) 70 C1: TAIYO YUDEN LMK325BJ106K-T 65 C2A: SANYO 6TPA47M V 80.6k IN = 3.6V C2B: AVX 0805ZC105KAT1A VOUT = 2.5V D1: MOTOROLA MBRM120T3 60 10 100 1000 10000 L1: MURATA LQN6C-4R7 M1: FAIRCHILD FDC638P LOAD CURRENT (mA) 1772 F01a R1: IRC LRC-LR1206-01-R030F *OUTPUT RIPPLE WAVEFORMS FOR THE CIRCUIT OF FIGURE 1 APPEAR IN FIGURE 2. 1772 F01b
Figure 1. High Effi ciency, High Output Current 2.5V/2A Regulator
1772bfa 1
