LT3905 - Boost DC/DC Converter with APD Current Monitor
Features
- 65V, 350mA Internal DMOS Switch
- Integrated Schottky Diode
- 2% Accurate APD Current Monitoring Over the 3μA to 3mA Range
- Single Resistor Programs Maximum APD Current
- Fast APD Current Limiter with Indicator
- Programmable Loss-of-Signal Indicator
- CTRL Pin Adjusts Output Voltage
- Programmable VIN Undervoltage Lockout
- High Efficiency Step-Up Converter
- Selectable 1MHz/2MHz Switching Frequency
- Internally Compensated
- Internal Soft-Start
- 2.7V to 12V VIN Range
- Low Shutdown Current: <1μA
Typical Application
Description
The LT®3905 is a fixed frequency current-mode step-up converter designed to bias avalanche photodiodes (APD) in optical receivers. The LT3905 features high side APD current monitoring over four decades of dynamic range with better than 2% relative accuracy over the 3μA to 3mA range.
The maximum APD current is programmed with a single resistor, and a fast current limiter with indicator protects the APD during overload conditions. Adjustable output voltage provides dynamic bias control, and an adjustable loss-of-signal indicator flags low APD current.
Coupled with the integrated DMOS power switch and Schottky rectifier, the LT3905 provides a compact total solution with few external components and low solution cost. Constant switching frequency results in predictable output noise that is easy to filter.
The LT3905 is available in the tiny footprint (3mm × 3mm) 16-Lead QFN 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 |
|---|---|---|---|---|---|
| LT3905EUD#PBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3905EUD#TRPBF | 3x3 QFN-16 | UD | E | 05-08-1691 | Yes |
| LT3905IUD#PBF | 3x3 QFN-16 | UD | I | 05-08-1691 | Yes |
| LT3905IUD#TRPBF | 3x3 QFN-16 | UD | I | 05-08-1691 | 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 | |
|---|---|---|---|---|---|---|
| LT3905EUD#PBF | 3x3 QFN-16 | E | $3.64 | $2.55 | Yes | |
| LT3905EUD#TRPBF | 3x3 QFN-16 | E | $2.61 | Yes | ||
| LT3905IUD#PBF | 3x3 QFN-16 | I | $4.02 | $2.81 | Yes | |
| LT3905IUD#TRPBF | 3x3 QFN-16 | I | $2.87 | 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 |
|---|---|---|---|
| DC1956A | LT3905 Demo Board | Boost with APD Current Monitor, 2.7V ≤ VIN ≤ 12V, Vout = 50V @ 2mA | $125.00 | |
| Buy Now | |||
Applications
- APD Bias
- PIN Diode Bias
- Optical Receivers and Modules
- Fiber Optic Network Equipment
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Design Tools
LTspice
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Models for the following parts are available in LTspice:
LT3905
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.
