| Feature | SN51DP | ULN2003A | ULN2803A | |-----------------------|-----------------|-----------------|-----------------| | Number of channels | 7 | 7 | 8 | | Output voltage max | 50V (or 100V) | 50V | 50V | | Output current (cont.)| 500 mA | 500 mA | 500 mA | | Input compatibility | TTL/CMOS (3-24V)| TTL/CMOS (3-5V) | TTL/CMOS (3-5V) | | Internal base resistor| Yes (2.7k) | Yes (2.7k) | Yes (2.7k) | | Package | 16-pin DIP | 16-pin DIP/SOIC | 18-pin DIP | | Clamp diodes | Yes | Yes | Yes |
The Darlington pair configuration multiplies the current gain, meaning you can drive heavy loads without needing additional driver transistors or MOSFETs. How to Use the SN51DP: Typical Application Circuits The SN51DP datasheet PDF includes several reference circuits. Let’s explore the most common ones. 1. Driving DC Relays and Solenoids This is the most popular application. Connect the relay coil between V+ (e.g., 24V) and the output pin. Connect the COM pin to the same V+. The internal diode will clamp inductive kickback. sn51dp datasheet pdf
| Pin No. | Name | Description | |---------|-------------|----------------------------------------------| | 1 | IN 1 | Input channel 1 | | 2 | IN 2 | Input channel 2 | | 3 | IN 3 | Input channel 3 | | 4 | IN 4 | Input channel 4 | | 5 | IN 5 | Input channel 5 | | 6 | IN 6 | Input channel 6 | | 7 | IN 7 | Input channel 7 | | 8 | GND | Ground (common for inputs and logic) | | 9 | COM | Common free-wheeling diode cathode (VCC for inductive loads) | | 10 | OUT 7 | Output channel 7 (open collector) | | 11 | OUT 6 | Output channel 6 | | 12 | OUT 5 | Output channel 5 | | 13 | OUT 4 | Output channel 4 | | 14 | OUT 3 | Output channel 3 | | 15 | OUT 2 | Output channel 2 | | 16 | OUT 1 | Output channel 1 | | Feature | SN51DP | ULN2003A | ULN2803A