ULN2003

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

7 of 10

www.unisonic.com.tw

QW-R113-001.O

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APPLICATION NOTES

This UTC ULN2003 has no protection functions for over-current and over-voltage. If the applied situation includes

over-current or over-voltage, this IC may be destroyed. We should take care of the systems design with this IC. The

OUTPUT, COMMON and GND lines should be designed carefully，because the IC may be destroyed due to

short-circuit between outputs, air contamination fault, or fault by improper grounding.

The UTC ULN2003 is a darlington driver array. When it is applied with a general logic circuit such as TTL or

CMOS, resistors should be connected in series to every input to achieve a stable input current.

When the load is connected between the output and the power supply, the COMMON pin should be shorted to the

power supply to protect the IC from extra swing voltage.

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NOTICE ON PRODUCT USE

(1) The absolute maximum ratings should be not exceeded, even for a moment, otherwise the device may be

breakdown, damaged or deteriorated, and even injury by explosion or combustion.

(2) The power supply fuse should be used to prevent a continuous large current from the over current situation

and IC failure. The improper wiring layout and an abnormal pulse noise from the wiring or load both can cause a

large continuous current and even the breakdown, and finally can lead smoke or ignition. So we should design

carefully considering fuse capacity, fusing time and insertion circuit location, the effects of a large current can be

improved.

(3) When the inductive load is applied such as motor coil, it can cause the device malfunction or breakdown due to

the current resulting from the inrush current at power ON or the negative current resulting from the back

electromotive force at power OFF, so a protection circuit should be designed. When using build-in protection

functions IC, a stable power supply is required, otherwise the protection function may not operate and cause IC

breakdown. IC breakdown may result injury, smoke or ignition.

(4) The devices should not be mounted in the wrong orientation or incorrectly, and the positive and negative

terminals of power supplies should also are connected properly, otherwise the current or power consumption may

exceed the absolute maximum rating, also it may cause the device breakdown, damage or deterioration, and may

result injury by explosion or combustion. In addition, any device should not be used when it is applied the current

with mounted in the wrong orientation or incorrectly even just one time.

(5) The careful selection of external components is also important, such as inputs and negative feedback

capacitors, load components (such as speakers), power amp and regulator. If a large leakage current flow the input

or negative feedback capacitors, the IC output DC voltage will be increased. If this output voltage is connected to a

speaker with low input withstand voltage, the smoke or ignition can be caused for over-current or IC failure, even the

smoke or ignition from the IC itself. In addition, please also pay attention to the Bridge Tied Load (BTL) connection

type IC that inputs output DC voltage to a speaker directly.

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POINTS TO REMEMBER ON PRODUCT USE

(1) Heat Dissipation Design

An inadequate IC heat dissipation design can reduce the IC life, deterioration of IC characteristics, even IC

breakdown. When the IC is applied with a large current flow such as power amp, regulator and so on, the careful

heat dissipation design should be implemented, not to exceed the maximum ratings of junction temperature (Tj).

Meanwhile, also please pay attention to the effect of IC heat dissipation on peripheral components.

(2) Back-EMF

Being the effect of back-EMF, a current can flow back to the motor’s power supply when a motor rotates in the

reverse direction, stops or slows down suddenly. If the power supply has a low current sink capability, the device’s

motor power supply and output pins might be influenced for excessing the absolute maximum ratings. In the system

design, we should take the effect of back-EMF into consideration to avoid the accident.