Datasheet LTC3772B (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Micropower No RSENSE Constant Frequency Step-Down DC/DC Controller |
| Pages / Page | 20 / 1 — FEATURES. DESCRIPTIO. No Current Sense Resistor Required. High Output … |
| File Format / Size | PDF / 331 Kb |
| Document Language | English |
FEATURES. DESCRIPTIO. No Current Sense Resistor Required. High Output Currents Easily Achieved. Internal Soft-Start Ramps VOUT
Model Line for this Datasheet
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LTC3772B Micropower No RSENSE Constant Frequency Step-Down DC/DC Controller
U FEATURES DESCRIPTIO
■
No Current Sense Resistor Required
The LTC®3772B is a constant frequency current mode ■
High Output Currents Easily Achieved
step-down DC/DC controller in a low profile 8-lead SOT-23 ■
Internal Soft-Start Ramps VOUT
(ThinSOTTM) and a 3mm × 2mm DFN package. The No ■
Wide V
TM
IN Range: 2.75V to 9.8V
RSENSE architecture eliminates the need for a current ■ Low Dropout: 100% Duty Cycle sense resistor, improving efficiency and saving board ■ Constant Frequency 550kHz Operation space. ■ Low Ripple Pulse Skipping Operation at Light Load The LTC3772B automatically switches into pulse skipping ■ Output Voltage as Low as 0.8V operation at light loads. It consumes only 200µA of quies- ■ ±1.5% Voltage Reference Accuracy cent current under a no-load condition. ■ Current Mode Operation for Excellent Line and Load Transient Response The LTC3772B incorporates an undervoltage lockout fea- ■ Only 8µA Supply Current in Shutdown ture that shuts down the device when the input voltage ■ Low Profile 8-Lead SOT-23 (1mm) and falls below 2V. To maximize the runtime from a battery (3mm × 2mm) DFN (0.75mm) Packages source, the external P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High switch-
U
ing frequency of 550kHz allows the use of a small inductor
APPLICATIO S
and capacitors. An internal soft-start smoothly ramps the ■ 1- or 2-Cell Li-Ion Battery-Powered Applications output voltage from zero to its regulation point. ■ Wireless Devices , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ■ Portable Computers ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. ■ Distributed Power Systems All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5731694, 6127815.
U TYPICAL APPLICATIO Efficiency and Power Loss vs Load Current 550kHz Micropower Step-Down DC/DC Converter (Figure 5 Circuit)
680pF 100 10 20k V I IN 90 TH/RUN VIN 2.75V TO 9.8V LTC3772B 80 10µF EFFICIENCY 1 GND PGATE 70 POWER LOSS (W) 82.5k 3.3µH V 60 OUT VFB SW 2.5V 50 0.1 2A 47µF 40 22pF 174k EFFICIENCY (%) POWER LOSS 30 0.01 3772B TA01 20 10 VIN = 3.3V VIN = 5V 0 0.001 1 10 100 1000 10000 LOAD CURRENT (mA) 3772B TA01b 3772bfa 1
U FEATURES DESCRIPTIO
■
No Current Sense Resistor Required
The LTC®3772B is a constant frequency current mode ■
High Output Currents Easily Achieved
step-down DC/DC controller in a low profile 8-lead SOT-23 ■
Internal Soft-Start Ramps VOUT
(ThinSOTTM) and a 3mm × 2mm DFN package. The No ■
Wide V
TM
IN Range: 2.75V to 9.8V
RSENSE architecture eliminates the need for a current ■ Low Dropout: 100% Duty Cycle sense resistor, improving efficiency and saving board ■ Constant Frequency 550kHz Operation space. ■ Low Ripple Pulse Skipping Operation at Light Load The LTC3772B automatically switches into pulse skipping ■ Output Voltage as Low as 0.8V operation at light loads. It consumes only 200µA of quies- ■ ±1.5% Voltage Reference Accuracy cent current under a no-load condition. ■ Current Mode Operation for Excellent Line and Load Transient Response The LTC3772B incorporates an undervoltage lockout fea- ■ Only 8µA Supply Current in Shutdown ture that shuts down the device when the input voltage ■ Low Profile 8-Lead SOT-23 (1mm) and falls below 2V. To maximize the runtime from a battery (3mm × 2mm) DFN (0.75mm) Packages source, the external P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High switch-
U
ing frequency of 550kHz allows the use of a small inductor
APPLICATIO S
and capacitors. An internal soft-start smoothly ramps the ■ 1- or 2-Cell Li-Ion Battery-Powered Applications output voltage from zero to its regulation point. ■ Wireless Devices , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ■ Portable Computers ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. ■ Distributed Power Systems All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5731694, 6127815.
U TYPICAL APPLICATIO Efficiency and Power Loss vs Load Current 550kHz Micropower Step-Down DC/DC Converter (Figure 5 Circuit)
680pF 100 10 20k V I IN 90 TH/RUN VIN 2.75V TO 9.8V LTC3772B 80 10µF EFFICIENCY 1 GND PGATE 70 POWER LOSS (W) 82.5k 3.3µH V 60 OUT VFB SW 2.5V 50 0.1 2A 47µF 40 22pF 174k EFFICIENCY (%) POWER LOSS 30 0.01 3772B TA01 20 10 VIN = 3.3V VIN = 5V 0 0.001 1 10 100 1000 10000 LOAD CURRENT (mA) 3772B TA01b 3772bfa 1
