Datasheet LT1941 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Triple Monolithic Switching Regulator |
| Pages / Page | 24 / 1 — FEATURES. DESCRIPTION. Wide Input Range: 3.5V to 25V. Three Switching … |
| File Format / Size | PDF / 237 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Range: 3.5V to 25V. Three Switching Regulators with Internal Power
Model Line for this Datasheet
Text Version of Document
LT1941 Triple Monolithic Switching Regulator
FEATURES DESCRIPTION
n
Wide Input Range: 3.5V to 25V
The LT®1941 is a triple current mode DC/DC converter n
Three Switching Regulators with Internal Power
with internal power switches. Two of the regulators are
Switches: 3A Step-Down, 2A Step-Down,
step-down converters with 3A and 2A power switches.
1.5A Inverting/Boost
The third regulator can be confi gured as a boost, inverter n
Antiphase Switching Reduces Ripple
or SEPIC converter and has a 1.5A power switch. All n Independent Shutdown/Soft-Start Pins three converters are synchronized to a 1.1MHz oscillator. n Independent Power Good Indicators Ease Supply The two step-down converters run with opposite phase, Sequencing reducing input ripple current. The output voltages are n Input Voltage Power Good Indicators Monitor Input set with external resistor dividers and each regulator Supply has independent shutdown and soft-start circuits. Each n Uses Small Inductors and Ceramic Capacitors regulator generates a power good signal when its output n Constant 1.1MHz Switching Frequency is in regulation, easing power supply sequencing and n Thermally Enhanced 28-Lead TSSOP Package interfacing with microcontrollers and DSPs. The high switching frequency offers several advantages
APPLICATIONS
by permitting the use of small inductors and ceramic capacitors, leading to a very small triple output solution. n Cable Modems The constant switching frequency, combined with low n DSL Modems impedance ceramic capacitors, result in low, predictable n Distributed Power Regulation output ripple. With its wide input voltage range of 3.5V to n Wall Transformer Regulation 25V, the LT1941 regulates a broad array of power sources n Disk Drives from 4-cell batteries and 5V logic rails to unregulated wall n DSP Power transformers, lead acid batteries and distributed-power L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. supplies.
TYPICAL APPLICATION
V V OUT1 OUT2 VIN 4.7V TO 14V 130k 100k V 100k 100k 100k IN PGOOD1 PGOOD1
Start-Up Waveforms
5GOOD 5GOOD PGOOD2 PGOOD2 12GOOD 12GOOD PGOOD3 PGOOD3
with Sequencing
BOOST1 BOOST2 0.22μF V 3μH LT1941 0.22μF 3.3μH OUT1 RUN/SS 1.8V SW1 SW2 2V/DIV V 2.4A 13.7k 10.7k OUT2 FB1 FB2 3.3V VOUT1 3300pF 1000pF 1.4A 2V/DIV V V 33μF C1 C2 22μF VOUT2 7.32k 3.3k 10k 2.49k 5V/DIV 1.5nF 1.5nF RUNSS1 RUNSS2 SW3 BIAS1 VOUT3 10V/DIV 22μH 1μF 22nF NFB BIAS2 V I OUT3 VIN(AVE) –12V 133k 13.7k VC3 1A/DIV 350mA* 22μH FB3 RUNSS3 PGOOD2 5V/DIV GND 1.5k 1.5nF 1941 F01b 10μF 10μF 2ms/DIV 1941 F01 *240mA AT VIN = 5V, 550mA AT VIN = 12V
Figure 1. Triple Output Power Supply: 3.3V, 1.8V, –12V
1941fb 1
FEATURES DESCRIPTION
n
Wide Input Range: 3.5V to 25V
The LT®1941 is a triple current mode DC/DC converter n
Three Switching Regulators with Internal Power
with internal power switches. Two of the regulators are
Switches: 3A Step-Down, 2A Step-Down,
step-down converters with 3A and 2A power switches.
1.5A Inverting/Boost
The third regulator can be confi gured as a boost, inverter n
Antiphase Switching Reduces Ripple
or SEPIC converter and has a 1.5A power switch. All n Independent Shutdown/Soft-Start Pins three converters are synchronized to a 1.1MHz oscillator. n Independent Power Good Indicators Ease Supply The two step-down converters run with opposite phase, Sequencing reducing input ripple current. The output voltages are n Input Voltage Power Good Indicators Monitor Input set with external resistor dividers and each regulator Supply has independent shutdown and soft-start circuits. Each n Uses Small Inductors and Ceramic Capacitors regulator generates a power good signal when its output n Constant 1.1MHz Switching Frequency is in regulation, easing power supply sequencing and n Thermally Enhanced 28-Lead TSSOP Package interfacing with microcontrollers and DSPs. The high switching frequency offers several advantages
APPLICATIONS
by permitting the use of small inductors and ceramic capacitors, leading to a very small triple output solution. n Cable Modems The constant switching frequency, combined with low n DSL Modems impedance ceramic capacitors, result in low, predictable n Distributed Power Regulation output ripple. With its wide input voltage range of 3.5V to n Wall Transformer Regulation 25V, the LT1941 regulates a broad array of power sources n Disk Drives from 4-cell batteries and 5V logic rails to unregulated wall n DSP Power transformers, lead acid batteries and distributed-power L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. supplies.
TYPICAL APPLICATION
V V OUT1 OUT2 VIN 4.7V TO 14V 130k 100k V 100k 100k 100k IN PGOOD1 PGOOD1
Start-Up Waveforms
5GOOD 5GOOD PGOOD2 PGOOD2 12GOOD 12GOOD PGOOD3 PGOOD3
with Sequencing
BOOST1 BOOST2 0.22μF V 3μH LT1941 0.22μF 3.3μH OUT1 RUN/SS 1.8V SW1 SW2 2V/DIV V 2.4A 13.7k 10.7k OUT2 FB1 FB2 3.3V VOUT1 3300pF 1000pF 1.4A 2V/DIV V V 33μF C1 C2 22μF VOUT2 7.32k 3.3k 10k 2.49k 5V/DIV 1.5nF 1.5nF RUNSS1 RUNSS2 SW3 BIAS1 VOUT3 10V/DIV 22μH 1μF 22nF NFB BIAS2 V I OUT3 VIN(AVE) –12V 133k 13.7k VC3 1A/DIV 350mA* 22μH FB3 RUNSS3 PGOOD2 5V/DIV GND 1.5k 1.5nF 1941 F01b 10μF 10μF 2ms/DIV 1941 F01 *240mA AT VIN = 5V, 550mA AT VIN = 12V
Figure 1. Triple Output Power Supply: 3.3V, 1.8V, –12V
1941fb 1
