LT3688 - Dual 800mA Step-Down Switching Regulator with Power-On Reset and Watchdog Timer
Features
- Wide Input Range:
Operation from 3.8V to 36V - Low Ripple (<25mVP-P ) Burst Mode Operation:
IQ = 115μA at 12VIN to 3.3V and 5V - Programmable, Defeatable Window Watchdog Timer
- Two Independently Programmable Power-On-Reset Timers
- Synchronizable, Adjustable 350kHz-2.2MHz Switching Frequency
- Two 800mA Output Switching Regulators with Internal Power Switches
- Programmable Input Undervoltage Lockout with Hysteresis
- Thermally Enhanced 24-Pin TSSOP and 4mm × 4mm QFN Packages
AEC-Q100 data available for specific packages
Typical Application
Description
The LT3688 is an adjustable frequency (350kHz to 2.2MHz) dual monolithic step-down switching regulator with two power-on reset timers and a watchdog timer. The regulator operates off inputs up to 36V. Low ripple Burst Mode® operation maintains high efficiency at low output current while keeping output ripple below 25mV in a typical application, with input quiescent current of just 115μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low.
The reset and watchdog timeout periods are both adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation without false triggering. The open collector RST pins will pull down if the monitored output voltage drops 10% below the programmed value. The LT3688 watchdog timer monitors for watchdog falling edges grouped too close together or too far apart.
The LT3688 is available in 24-Pin TSSOP and 4mm × 4mm QFN packages, each with an exposed pad for low thermal resistance.
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 |
|---|---|---|---|---|---|
| LT3688EFE#PBF | TSSOP-24 | FE | E | 05-08-1771 | Yes |
| LT3688EFE#TRPBF | TSSOP-24 | FE | E | 05-08-1771 | Yes |
| LT3688EUF#PBF | 4x4 QFN-24 | UF | E | 05-08-1697 | Yes |
| LT3688EUF#TRPBF | 4x4 QFN-24 | UF | E | 05-08-1697 | Yes |
| LT3688HFE#PBF | TSSOP-24 | FE | H | 05-08-1771 | Yes |
| LT3688HFE#TRPBF | TSSOP-24 | FE | H | 05-08-1771 | Yes |
| LT3688IFE#PBF | TSSOP-24 | FE | I | 05-08-1771 | Yes |
| LT3688IFE#TRPBF | TSSOP-24 | FE | I | 05-08-1771 | Yes |
| LT3688IUF#PBF | 4x4 QFN-24 | UF | I | 05-08-1697 | Yes |
| LT3688IUF#TRPBF | 4x4 QFN-24 | UF | I | 05-08-1697 | 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 | |
|---|---|---|---|---|---|---|
| LT3688EFE#PBF | TSSOP-24 | E | $5.36 | $3.75 | Yes | |
| LT3688EFE#TRPBF | TSSOP-24 | E | $3.81 | Yes | ||
| LT3688EUF#PBF | 4x4 QFN-24 | E | $5.14 | $3.60 | Yes | |
| LT3688EUF#TRPBF | 4x4 QFN-24 | E | $3.66 | Yes | ||
| LT3688HFE#PBF | TSSOP-24 | H | $6.31 | $4.42 | Yes | |
| LT3688HFE#TRPBF | TSSOP-24 | H | $4.48 | Yes | ||
| LT3688IFE#PBF | TSSOP-24 | I | $5.96 | $4.17 | Yes | |
| LT3688IFE#TRPBF | TSSOP-24 | I | $4.23 | Yes | ||
| LT3688IUF#PBF | 4x4 QFN-24 | I | $5.73 | $4.01 | Yes | |
| LT3688IUF#TRPBF | 4x4 QFN-24 | I | $4.07 | 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 |
|---|---|---|---|
| DC1439A | LT3688EFE Demo Board | 7V ≤ VIN ≤ 36V, 60V Transients, Vout1 = 5V @ 0.8A, Vout2 = 3.3V @ 0.8A | Contact Factory | |
| Buy Now | |||
Designed for Automotive and Transportation Applications
AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LT3688HFE#PBF | TSSOP-24 | H | $6.31 | $4.42 | Yes | |
| LT3688HFE#TRPBF | TSSOP-24 | H | $4.48 | Yes | ||
| LT3688IFE#PBF | TSSOP-24 | I | $5.96 | $4.17 | Yes | |
| LT3688IFE#TRPBF | TSSOP-24 | I | $4.23 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Automotive Electronic Control Units
- Industrial Power Supplies
- High-Reliability μProcessor Systems
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Design Tools
LTspice
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LT3688
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.
