Features
The 500 mA rated collector current ULN2803A device is a 50 V, 500 mA Darlington (single output) transistor array. The device consists of eight NPNs.
Darlington Pair with High Voltage Output High Voltage Output: 50 V Universal Cathode Clamp Diode Output Clamp Diode for Switching Inductive Loads. The current rating of each collector is 500 mA for inputs compatible with various types of logic Darlington pairs. The Darlingtons are paralleled for higher current capability.
Applications include relay drives, hydraulic hammer drives,
Relay drivers, lamp drivers, display drivers (LED and gas discharge), line drivers and logic buffers. The Hydraulic Hammer Driver ULN2803A device has a 2.7-kΩ series base resistor per Darlington pair of lamp drivers for use directly with display drivers (LED and gas discharge) TTL or 5-V CMOS devices.
Line Driver Device Information (1)
Logic Buffer Part Number Package Body Dimensions (nom) Stepper Motor ULN2803ADW SOIC (18) 11.55 mm x 7.50 mm

DETAILED DESCRIPTION Overview This standard device has proven ubiquity and versatility in a wide range of applications. This is due to the integrated 8 Darlington transistors capable of sinking 500mA and wide gpio range.
ULN2803A consists of eight pairs of high voltage and high current NPN Darlington transistors. All unit functions share open emitter and collector outputs. To maximize their effectiveness, these units contain suppressed inductive load diodes. The ULN2803A has a series base resistor on each Darlington pair, thus allowing direct TTL or CMOS operation with a supply voltage of 5 V or 3.3 V. The ULN2803A provides solutions to many interface needs, including solenoid valves, relays, lights, small motors and LEDs.
If the application requires more current than a single output can accommodate, paralleling can be used to accommodate it.
output.
Functional block diagram

Feature description
Each channel of the ULN2803A consists of Darlington connected NPN transistors. This connection results in a transistor with very high current gain. A very high beta allows high output currents to drive very low input currents, essentially equivalent to operation with low GPIO voltages.
The GPIO voltage is converted to base current through a 2.7-kΩ resistor connected between the input and the input.
The foundation of the Predriver Darlington NPN.
A diode connected between the output and the COM pin is used to suppress the inductive load from the excitation when the NPN driver is off (stops sinking) and the coil causes reverse current to flow into the coil power supply through the kickback diode.
In normal operation, the diode on the base and the collector-to-emitter pins will be reverse biased. If these diodes are forward biased the internal parasitic NPN transistors will draw (nearly equal) current from other (nearby) devices.
pins.
Device Functional Modes Inductive Load Driving When the COM pin is connected to the coil supply voltage, the ULN2803A is capable of driving inductive loads and suppressing kickback voltage through an internal free-spinning diode.
Resistive Load Drive When driving a resistive load, COM can be left unconnected or connected to the load voltage supply. If multiple power supplies are used, connect to the power supply with the highest voltage.

APPLICATIONS AND IMPLEMENTATION NOTES The information in the Applications section below is not part of the TI component specification and ti does not warrant its accuracy or completeness. The customer of Texas Instruments is responsible for determining the suitability of the part for its purpose. Customers should verify and test their design implementation to confirm system functionality.
Application Information
The ULN2803A is typically used to drive high voltage and/or current peripherals from microcontrollers or logic devices. These conditions cannot be tolerated. The following designs are common applications for the ULN2803A, driving inductive loads. This includes motors, solenoids and relays. Each load type can be modeled by what you see in .
typical application

Detailed Design Procedure When using the ULN2803A in a coil drive application, determine the following:
Input Voltage Range Temperature Range Output and Drive Current Power Consumption Drive Current Coil Current is determined by Coil Voltage (VSUP), Coil Resistance and Output Low Voltage (vol or VCE(SAT)).
electrical characteristics.
The number of power losses and temperature drive coils depends on the coil current and on-chip power dissipation. To determine the number of possible coils, use Equation 2 to calculate the on-chip power dissipation PD of the ULN2803A
n is the number of simultaneously activated channels.
voli is the output pin voltage of the load current ili. This is the same as VCE(SAT) (2) To guarantee the reliability of the ULN2803A and the system, the on-chip power dissipation must be lower than or equal to the maximum allowable power dissipation (pd), determined by Equation 3. Pd(max)=()ttj(max)a-qja
where Tj(max) is the target maximum junction temperature.
Ta is the working ambient temperature.
θja is the junction of the package-to-ambient thermal resistance. (3)
Ti recommends limiting the die attach temperature of the ULN2803A IC to <125°C. The IC connection temperature is proportional to the on-chip power dissipation.

Power Recommendations No power is required for this part; however, the COM pins are usually tied to system power.
In this case, make sure that the output voltage does not seriously exceed the COM pin voltage. This will severely forward bias the flyback diode, causing a large current to flow into the COM, possibly damaging the chip metal or overheating the parts.
Layout Guidelines Thin traces are available for the inputs due to the low current logic typically used to drive the ULN2803A.
Take care to separate input channels as much as possible to eliminate crosstalk. TI recommends using thick traces for the output, in order to drive the high currents required. The thickness of the line can be determined by the trace.
The current density of the material and the required drive current.
Since all channel currents go back to a common transmitter, it is best to adjust the trace width to be wide. Some applications require up to 2.5 A.
layout example

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Electrostatic discharge precautions This integrated circuit can be damaged by electrostatic discharge. Texas Instruments recommends the use of appropriate precautions. Failure to follow proper operation and installation procedures may result in damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits can be more susceptible to damage because very small parameter changes can cause the device to not meet its published specifications.
SLYZ022-TI Glossary.
This glossary lists and explains terms, abbreviations and definitions.
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