DocumentationDatasheet
Application Note
- AN45 - Measurement and Control Circuit Collection
- AN51 - Power Conditioning for Notebook and Palmtop Systems
- AN66 - Linear Technology Magazine Circuit Collection, Volume II
Reliability Data
cad_symbol
Features
- Extremely Low Dropout
- Low Cost
- Fixed 5V Output, Trimmed to ±1%
- 700µA Quiescent Current
- 3-Pin TO-92 Package
- 1mV Line Regulation
- 5mV Load Regulation
- Thermal Limit
- 4A Output Current Guaranteed
Typical Application
Description
The LT1123 is a 3-pin bipolar device designed to be used in conjunction with a discrete PNP power transistor to form an inexpensive low dropout regulator. The LT1123 consists of a trimmed bandgap reference, error amplifier, and a driver circuit capable of sinking up to 125mA from the base of the external PNP pass transistor. The LT1123 is designed to provide a fixed output voltage of 5V.The drive pin of the device can pull down to 2V at 125mA (1.4V at 10mA). This allows a resistor to be used to reduce the base drive available to the PNP and minimize the power dissipation in the LT1123. The drive current of the LT1123 is folded back as the feedback pin approaches ground to further limit the available drive current under short circuit conditions.
Total quiescent current for the LT1123 is only 700µA. The device is available in a low cost TO-92 package.
SOT-223,TO-92
Package Variations and Pricing
| Part Number | Package | Pins | Temp | Price (1-99) |
Price (1k)* |
|---|---|---|---|---|---|
| LT1123CST#PBF | SOT | 3 | C | $2.08 | $1.65 |
| LT1123CST#TRPBF | SOT | 3 | C | $1.71 | |
| LT1123CZ#PBF | TO-92 | 3 | C | $1.58 | $1.25 |
| LT1123CZ#TRPBF | TO-92 | 3 | C | $1.31 | |
| LT1123CST | SOT | 3 | C | $4.16 | $3.30 |
| LT1123CST#TR | SOT | 3 | C | $3.42 | |
| LT1123CZ | TO-92 | 3 | C | $3.16 | $2.50 |
| LT1123CZ#TR | TO-92 | 3 | C | $2.62 |
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.