Slkor ULN2803AS: 50V Withstand‑voltage 500mA SOP‑18 Octal Darlington Transistor Array

ULN2803AS is an octal NPN Darlington transistor array in SOP-18 package, with built-in free-wheeling clamp diodes and open-collector output structure. It performs level conversion and load driving between low-logic-level digital circuits such as TTL / CMOS and high-voltage, high-current loads including relays and indicator lamps. Its operating temperature ranges from 0℃ to 70℃. It is widely adopted for multi-channel load-driving applications in computer, industrial control and consumer-electronic equipment.

1. Core Product Parameters

1. Output voltage: maximum 50V
2. Input voltage: maximum 30V
3. Continuous collector current per channel: maximum 500mA
4. Continuous base current per channel: maximum 25mA
5. Ambient operating temperature: 0℃~70℃
6. Storage temperature: -55℃~+150℃
7. Maximum junction temperature: 125℃
8. Thermal resistance θJA: 55℃/W
9. Output leakage current: maximum 50μA at 25℃, maximum 100μA at 70℃
10. Collector-Emitter saturation voltage: typical 0.85V~1.1V under different collector-current conditions, maximum 1.6V
11. Input turn-on current: typical 1.1mA at input voltage 3.85V, maximum 1.35mA
12. Input turn-on voltage: typical 1.70V~1.80V, maximum 2.4V~3.0V, varying with collector current
13. Input turn-off current: 50μA~100μA at 70℃
14. Input capacitance: typical 15pF, maximum 25pF
15. Turn-on and turn-off delay time: typical 0.25μs, maximum 1.0μs
16. Reverse leakage current of clamp diode: maximum 50μA at 25℃, maximum 100μA at 70℃
17. Forward voltage of clamp diode: typical 1.5V under 350mA current, maximum 2.0V
18. Package form: SOP-18

2. Core Product Features

1. Octal independent NPN Darlington transistor array in SOP-18 surface-mount package, compatible with automatic SMT assembly.
2. Open-collector output. Each channel integrates a built-in free-wheeling clamp diode to suppress transient high-voltage spikes induced by inductive loads.
3. TTL-compatible input level, supporting interfaces with various digital logic circuits including TTL, CMOS, PMOS and NMOS.
4. Each channel can sustain output voltage up to 50V and continuous collector current up to 500mA for driving loads with high voltage and high-current requirements.
5. Relatively fast turn-on and turn-off response, with low input capacitance, suitable for medium-speed switch-driving scenarios.
6. Clear limits for operating temperature, storage temperature and junction temperature, matching requirements of general-purpose industrial and consumer-electronic environments.

3. Main Application Fields

1. Relay driving: multi-channel relay-coil driving for industrial control boards and intelligent equipment.
2. Indicator lamp and LED array driving: high-current driving for multi-channel indicator lamps and LED arrays.
3. Printing equipment: driving printing components such as print hammers.
4. Industrial control systems: driving multi-channel resistive and inductive loads for PLC peripherals and industrial controllers.
5. Consumer-electronic devices: multi-channel load-switch driving for main control boards of household appliances.
6. Digital-interface level conversion: interface conversion from low-voltage logic signals to high-voltage high-current loads.

4. Engineering Design Recommendations

1. Current control: Do not exceed the maximum continuous collector current of 500mA per channel and maximum continuous base current of 25mA per channel. When multiple channels operate under large-current conditions simultaneously, evaluate thermal performance according to thermal resistance 55℃/W and prevent junction temperature from exceeding 125℃.
2. Inductive-load handling: When driving inductive loads such as relay coils, utilize the internal clamp diodes inside the chip in the load loop to absorb reverse transient voltage and protect device outputs.
3. Voltage constraints: Input pin voltage shall not exceed 30V and output pin voltage shall not exceed 50V to avoid permanent device damage.
4. Timing and load consideration: Turn-on and turn-off delays range from nanoseconds to microseconds. Switching delays shall be considered for timing-critical designs.
5. PCB layout: Widen high-current traces to reduce trace heating. Ensure reliable ground connection for ground pins to mitigate interference.
6. Temperature management: Keep ambient operating temperature within 0℃~70℃, otherwise electrical parameters will be degraded. Maintain storage temperature between -55℃~+150℃.

5. Product Summary

ULN2803AS is an octal Darlington transistor array in SOP-18 package with open-collector outputs and integrated clamp diodes. It converts low-level logic signals from TTL or CMOS circuits into high-voltage high-current driving capability, and is widely used for driving multi-channel relays, indicator lamps and inductive loads. All maximum ratings for current, voltage and temperature must be strictly followed with proper thermal evaluation in practical engineering. It is commonly deployed for multi-channel load driving in industrial controls, computer peripherals and various consumer-electronic products.

About Slkor：

SLKOR's product portfolio includes discrete semiconductor devices such as diodes, transistors, and power devices, as well as integrated circuits such as linear regulators, DC-DC converters, interface chips, Hall sensors, ADCs, and battery management systems (BMS)

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