Datasheet LTC3772 (Analog Devices)
| Hersteller | Analog Devices |
| Beschreibung | Micropower No RSENSE Constant Frequency Step-Down DC/DC Controller |
| Seiten / Seite | 20 / 1 — FEATURES. DESCRIPTIO. No Current Sense Resistor Required. A No-Load … |
| Dateiformat / Größe | PDF / 259 Kb |
| Dokumentensprache | Englisch |
FEATURES. DESCRIPTIO. No Current Sense Resistor Required. A No-Load Quiescent Current. High Output Currents Easily Achieved
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LTC3772 Micropower No RSENSE Constant Frequency Step-Down DC/DC Controller
U FEATURES DESCRIPTIO
■
No Current Sense Resistor Required
The LTC®3772 is a constant frequency current mode ■
40
µ
A No-Load Quiescent Current
step-down DC/DC controller in a low profile 8-lead SOT-23 ■
High Output Currents Easily Achieved
(ThinSOTTM) and a 3mm × 2mm DFN package. The No ■
Internal Soft-Start Ramps V
TM
OUT
RSENSE architecture eliminates the need for a current ■
Wide VIN Range: 2.75V to 9.8V
sense resistor, improving efficiency and saving board ■ Low Dropout: 100% Duty Cycle space. ■ Constant Frequency 550kHz Operation The LTC3772 automatically switches into Burst Mode ■ Low Ripple Burst Mode® Operation at Light Load operation at light loads to increase efficiency at low output ■ Output Voltage as Low as 0.8V current. It consumes only 40µA of quiescent current ■ ±1.5% Voltage Reference Accuracy under a no-load condition. ■ Current Mode Operation for Excellent Line and Load Transient Response The LTC3772 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
U
continuously in dropout (100% duty cycle). High switch-
APPLICATIO S
ing frequency of 550kHz allows the use of a small inductor 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 ■ Portable Computers , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. ■ Distributed Power Systems ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
U TYPICAL APPLICATIO 550kHz Micropower Step-Down DC/DC Converter Efficiency and Power Loss vs Load Current
100 10 680pF 20k V V IN = 3.3V I IN TH/RUN VIN 90 2.75V TO 9.8V LTC3772 V 1 10µF IN = 5V POWER LOSS (W) GND PGATE 80 82.5k 3.3µH VOUT 0.1 V 70 FB SW 2.5V V 2A IN = 5V VIN = 3.3V 47µF EFFICIENCY (%) 60 22pF 174k 0.01 3772 TA01 50 FIGURE 5 CIRCUIT 40 0.001 1 10 100 1000 10000 LOAD CURRENT (mA) 3772 TA01b 3772f 1
U FEATURES DESCRIPTIO
■
No Current Sense Resistor Required
The LTC®3772 is a constant frequency current mode ■
40
µ
A No-Load Quiescent Current
step-down DC/DC controller in a low profile 8-lead SOT-23 ■
High Output Currents Easily Achieved
(ThinSOTTM) and a 3mm × 2mm DFN package. The No ■
Internal Soft-Start Ramps V
TM
OUT
RSENSE architecture eliminates the need for a current ■
Wide VIN Range: 2.75V to 9.8V
sense resistor, improving efficiency and saving board ■ Low Dropout: 100% Duty Cycle space. ■ Constant Frequency 550kHz Operation The LTC3772 automatically switches into Burst Mode ■ Low Ripple Burst Mode® Operation at Light Load operation at light loads to increase efficiency at low output ■ Output Voltage as Low as 0.8V current. It consumes only 40µA of quiescent current ■ ±1.5% Voltage Reference Accuracy under a no-load condition. ■ Current Mode Operation for Excellent Line and Load Transient Response The LTC3772 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
U
continuously in dropout (100% duty cycle). High switch-
APPLICATIO S
ing frequency of 550kHz allows the use of a small inductor 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 ■ Portable Computers , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. ■ Distributed Power Systems ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
U TYPICAL APPLICATIO 550kHz Micropower Step-Down DC/DC Converter Efficiency and Power Loss vs Load Current
100 10 680pF 20k V V IN = 3.3V I IN TH/RUN VIN 90 2.75V TO 9.8V LTC3772 V 1 10µF IN = 5V POWER LOSS (W) GND PGATE 80 82.5k 3.3µH VOUT 0.1 V 70 FB SW 2.5V V 2A IN = 5V VIN = 3.3V 47µF EFFICIENCY (%) 60 22pF 174k 0.01 3772 TA01 50 FIGURE 5 CIRCUIT 40 0.001 1 10 100 1000 10000 LOAD CURRENT (mA) 3772 TA01b 3772f 1