LT1940 - Dual Monolithic 1.4A, 1.1MHz Step-Down Switching Regulator
Features
- Wide Input Voltage Range:
LT1940: 3.6V to 25V
LT1940L: 3.6V to 7V - Two 1.4A Output Switching Regulators with Internal Power Switches
- Constant 1.1MHz Switching Frequency
- Anti-Phase Switching Reduces Ripple
- Independent Shutdown/Soft-Start Pins
- Independent Power Good Indicators Ease Supply Sequencing
- Uses Small Inductors and Ceramic Capacitors
- Small 16-Lead Thermally Enhanced TSSOP Surface Mount Package
Typical Application
Description
The LT1940 is a dual current mode PWM step-down DC/DC converter with internal 2A power switches. Both converters are synchronized to a single 1.1MHz oscillator and run with opposite phases, reducing input ripple current. The output voltages are set with external resistor dividers, and each regulator has independent shutdown and soft-start circuits. Each regulator generates a power-good signal when its output is in regulation, easing power supply sequencing and interfacing with microcontrollers and DSPs.
The LT1940’s 1.1MHz switching frequency allows the use of tiny inductors and capacitors, resulting in a very small dual 1.4A output solution. Constant frequency and ceramic capacitors combine to produce low, predictable output ripple voltage. With its wide input range of 3.6V to 25V, the LT1940 regulates a wide variety of power sources, from 4-cell batteries and 5V logic rails to unregulated wall transformers, lead acid batteries and distributed-power supplies. The LT1940L is intended to operate from regulated 5V supplies. A current mode PWM architecture provides fast transient response with simple compensation components and cycle-by-cycle current limiting. Frequency foldback and thermal shutdown provide additional protection.
Packaging
CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.
For complete and up to date package information and drawings, please refer to our packaging page
| Part Number | Package | Code | Temp | Package Drawing |
RoHS |
|---|---|---|---|---|---|
| LT1940EFE#PBF | TSSOP-16 | FE | E | 05-08-1663 (BA) | Yes |
| LT1940EFE#TRPBF | TSSOP-16 | FE | E | 05-08-1663 (BA) | Yes |
| LT1940LEFE#PBF | TSSOP-16 | FE | E | 05-08-1663 (BA) | Yes |
| LT1940LEFE#TRPBF | TSSOP-16 | FE | E | 05-08-1663 (BA) | Yes |
Order Info
- Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
- Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
- Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LT1940EFE#PBF | TSSOP-16 | E | $5.29 | $3.70 | Yes | |
| LT1940EFE#TRPBF | TSSOP-16 | E | $3.82 | Yes | ||
| LT1940LEFE#PBF | TSSOP-16 | E | $3.86 | $2.70 | Yes | |
| LT1940LEFE#TRPBF | TSSOP-16 | E | $2.82 | Yes | ||
| Buy Now • Request Samples | ||||||
Demo Boards
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.| Part Number | Description | Price | Documentation |
|---|---|---|---|
| DC519A | LT1940EFE | Dual Output Buck, 2 Circuits, 4.8V ≤ VIN1 ≤ 14V, Vout1= 3.3V & 1.8V @ 1A; 6.8V ≤ VIN2 ≤ 25V, Vout2 = 5V & 3.3V @ 1.4A | $125.00 | |
| Buy Now | |||
Applications
- Disk Drives
- DSP Power Supplies
- Wall Transformer Regulation
- Distributed Power Regulation
- DSL Modems
- Cable Modems
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Design Tools
LTspice
LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice
Models for the following parts are available in LTspice:
LT1940
LTpowerCAD
The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD
Design tools for the following parts are available in LTpowerCAD:
LT1940
LT1940L
Technical Support
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
