ULN2803ADWR Discrete Semiconductor Products

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1. Description

The ULN2803ADWR device is a 50 V, 500 mA Darlington transistor array. The device consists of eight NPN Darlington pairs that feature high-voltage outputs with common-cathode clamp diodes for switching inductive loads. The collector-current rating of each Darlington pair is 500 mA. The Darlington pairs may be connected in parallel for higher current capability. Applications include relay drivers, hammer drivers, lamp drivers, display drivers (LED and gas discharge), line drivers, and logic buffers. The ULN2803A device has a 2.7-kΩ series base resistor for each Darlington pair for operation directly with TTL or 5-V CMOS devices.

2. Features

    1. 500-mA-Rated Collector Current (Single Output)

    2. High-Voltage Outputs: 50 V

    3. Output Clamp Diodes

    4. Inputs Compatible With Various Types of Logic

3. Applications

    1. Relay Drivers

    2. Hammer Drivers

    3. Lamp Drivers

    4. Display Drivers (LED and Gas Discharge)

    5. Line Drivers

    6. Logic Buffers

    7. Stepper Motors

    8. IP Camera

    9. HVAC Valve and LED Dot Matrix

4. Pin Configuration 

5. Pin Functions

6. Feature Description

Each channel of ULN2803ADWR consists of Darlington connected NPN transistors. This connection creates the effect of a single transistor with a very-high current gain. The very high β allows for high output current drive with a very-low input current, essentially equating to operation with low GPIO voltages. The GPIO voltage is converted to base current through the 2.7-kΩ resistor connected between the input and base of the predriver Darlington NPN. The diodes connected between the output and COM pin are used to suppress the kick-back voltage from an inductive load that is excited when the NPN drivers are turned off (stop sinking) and the stored energy in the coils causes a reverse current to flow into the coil supply through the kick-back diode. In normal operation, the diodes on base and collector pins to emitter will be reverse biased. If these diode are forward biased, internal parasitic NPN transistors will draw (a nearly equal) current from other (nearby) device pins.