Datasheet LT1938 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | 25V, 2.2A, 2.8MHz Step-Down Switching Regulator |
| Pages / Page | 24 / 1 — FEATURES. DESCRIPTION. Wide Input Voltage Range: 3.6V to 25V. 2.2A … |
| File Format / Size | PDF / 271 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Voltage Range: 3.6V to 25V. 2.2A Maximum Output Current
Model Line for this Datasheet
Text Version of Document
LT1938 25V, 2.2A, 2.8MHz Step-Down Switching Regulator
FEATURES DESCRIPTION
■
Wide Input Voltage Range: 3.6V to 25V
The LT®1938 is an adjustable frequency (300kHz to ■
2.2A Maximum Output Current
2.8MHz) monolithic buck switching regulator that accepts ■
Adjustable Switching Frequency: 300kHz to 2.8MHz
input voltages up to 25V. A high efficiency 0.18Ω switch ■
Low Shutdown Current: IQ < 1µA
is included on the die along with a boost Schottky diode ■
Integrated Boost Diode
and the necessary oscillator, control and logic circuitry. ■ Power Good Flag Current mode topology is used for fast transient response ■ Saturating Switch Design: 0.18Ω On-Resistance and good loop stability. The LT1938’s high operating fre- ■ 1.265V Feedback Reference Voltage quency allows the use of small, low cost inductors and ■ Output Voltage: 1.265V to 20V ceramic capacitors resulting in low output ripple while ■ Soft-Start Capability keeping total solution size to a minimum. The low current ■ Small 10-Pin Thermally Enhanced (3mm × 3mm) shutdown mode reduces input supply current to less than DFN Package 1µA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A
APPLICATIONS
power good flag signals when VOUT reaches 90% of the programmed output voltage. The LT1938 is available in ■ Automotive Battery Regulation a 3mm × 3mm DFN package with Exposed Pad for low ■ Power for Portable Products thermal resistance. ■ Distributed Supply Regulation ■ Industrial Supplies , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ■ Wall Transformer Regulation
TYPICAL APPLICATION 3.3V Step-Down Converter Efficiency (VOUT = 3.3V)
VIN VOUT 4.5V TO 3.3V 90 25V 2.2A VIN = 7V VIN BD 85 OFF ON RUN/SS BOOST 80 0.47µF 16.2k 4.7µH VIN = 24V VIN = 12V VC SW 4.7µF 75 LT1938 RT 70 680pF PG BIAS 65 324k EFFICIENCY (%) 60.4k FB GND 60 200k 22µF 55 L: NEC PLC-0745-4R7 f = 800kHz 1938 TA01 50 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 LOAD CURRENT (A) 1938 G02 1938fa 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL ChARACTERISTICS TYPICAL PERFORMANCE ChARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION TYPICAL APPLICATION RELATED PARTS
FEATURES DESCRIPTION
■
Wide Input Voltage Range: 3.6V to 25V
The LT®1938 is an adjustable frequency (300kHz to ■
2.2A Maximum Output Current
2.8MHz) monolithic buck switching regulator that accepts ■
Adjustable Switching Frequency: 300kHz to 2.8MHz
input voltages up to 25V. A high efficiency 0.18Ω switch ■
Low Shutdown Current: IQ < 1µA
is included on the die along with a boost Schottky diode ■
Integrated Boost Diode
and the necessary oscillator, control and logic circuitry. ■ Power Good Flag Current mode topology is used for fast transient response ■ Saturating Switch Design: 0.18Ω On-Resistance and good loop stability. The LT1938’s high operating fre- ■ 1.265V Feedback Reference Voltage quency allows the use of small, low cost inductors and ■ Output Voltage: 1.265V to 20V ceramic capacitors resulting in low output ripple while ■ Soft-Start Capability keeping total solution size to a minimum. The low current ■ Small 10-Pin Thermally Enhanced (3mm × 3mm) shutdown mode reduces input supply current to less than DFN Package 1µA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A
APPLICATIONS
power good flag signals when VOUT reaches 90% of the programmed output voltage. The LT1938 is available in ■ Automotive Battery Regulation a 3mm × 3mm DFN package with Exposed Pad for low ■ Power for Portable Products thermal resistance. ■ Distributed Supply Regulation ■ Industrial Supplies , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ■ Wall Transformer Regulation
TYPICAL APPLICATION 3.3V Step-Down Converter Efficiency (VOUT = 3.3V)
VIN VOUT 4.5V TO 3.3V 90 25V 2.2A VIN = 7V VIN BD 85 OFF ON RUN/SS BOOST 80 0.47µF 16.2k 4.7µH VIN = 24V VIN = 12V VC SW 4.7µF 75 LT1938 RT 70 680pF PG BIAS 65 324k EFFICIENCY (%) 60.4k FB GND 60 200k 22µF 55 L: NEC PLC-0745-4R7 f = 800kHz 1938 TA01 50 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 LOAD CURRENT (A) 1938 G02 1938fa 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL ChARACTERISTICS TYPICAL PERFORMANCE ChARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION TYPICAL APPLICATION RELATED PARTS
