LT1786F - SMBus Programmable CCFL Switching Regulator
Features
- Wide Battery Input Range: 4.5V to 30V
- Grounded Lamp or Floating Lamp Configurations
- Open Lamp Protection
- Precision 100µA Full-Scale DAC Programming Current
- 2-Wire SMBus Interface
- Two Selectable SMBus Addresses
- DAC Setting Is Retained in Shutdown
Typical Application
Description
The LT1786F is a fixed frequency, current mode, switching regulator that provides the control function for Cold Cathode Fluorescent Lighting (CCFL). The IC includes an efficient high current switch, an oscillator, output drive logic, control circuitry and a micropower 6-bit 100µA full-scale current output DAC. The DAC provides simple “bits-to-lamp-current control” and communicates using the 2-wire SMBus serial interface. The LT1786F acts as an SMBus slave device using one of two selectable SMBus addresses set by the address pin ADR.On Power-up, the DAC output current assumes midrange or zero scale, depending on the logic state of the ADR pin.The entire IC can be shut down through the SMBSUS pin or by setting the SHDN bit = 1 in the SMBus command byte. Digital data for the DAC output current is retained internally and the supply current drops to 40µA for standby operation. The active low SHDN pin disables the CCFL control circuitry, but keeps the DAC alive. Supply current in this operating mode drops to 150µA.
The LT1786F control circuitry operates from a logic supply voltage of 3.3V or 5V. The IC also has a battery supply pin that operates from 4.5V to 30V. The LT1786F draws 6mA typical quiescent current. A 200kHz switching frequency minimizes magnetic component size. Current mode switching techniques with cycle-by-cycle limiting gives high reliability and simple loop frequency compensation. The LT1786F is available in a 16-pin narrow SO package.
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 |
|---|---|---|---|---|---|
| LT1786FCS#PBF | SO-16 | S | C | 05-08-1610 (S16) | Yes |
| LT1786FCS#TRPBF | SO-16 | S | C | 05-08-1610 (S16) | 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 | |
|---|---|---|---|---|---|---|
| LT1786FCS#PBF | SO-16 | C | $4.97 | $4.20 | Yes | |
| LT1786FCS#TRPBF | SO-16 | C | $4.32 | 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 |
|---|---|---|---|
| DC182A | LT1786FCS | FLOATING/GROUNDED CCFL POWER SUPPLY WITH SMBUS CONTROL (req. DC1223) | $175.00 | |
| Buy Now | |||
Companion Boards
| Part Number | Description | Price | Documentation |
|---|---|---|---|
| DC1223A-B | USB to SM-Bus/SPI Interface with Monitor | $400.00 | |
| Buy Now | |||
Applications
- Notebook and Palmtop Computers
- Portable Instruments
- Personal Digital Assistants
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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:
LT1786F
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.
