ULN2003

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

6 of 10

www.unisonic.com.tw

QW-R113-001.J

APPLICATION NOTES

This UTC ULN2003 does not include built-in protection circuits for over-current or over-voltage. If this IC is

subjected to over-current or over-voltage, it may be destroyed. Hence, the utmost care must be taken when systems

which incorporate this IC are designed. Utmost care is necessary in the design of the output line, COMMON and

GND line since 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, and can be directly coupled to a general logic circuit such as TTL

or CMOS. Resistors are connected in series to each of the inputs to achieve a stable input current.

The load should be connected between the output and the power supply. To protect the IC from excessive swing

voltage, the COMMON pin (Pin 9) should be connected to the power supply.

The UTC ULN2003 can absorb the surge current because of the on-chip diode. The bottom Figure shows the

configuration of the on-chip diode.

In the construction of the surge-absorbing diode, there is parasitic PNP, output pin for emitter, COMMON pin for

base and the substrate (P-sub) for collector. When the diode is on, current flows from the output pin to the substrate.

When using the surge-absorbing diode, appropriate measures should be taken for the thermal characteristics of the

design considering the current. For example, when motor back-rush current or other conditions that can create

continued surge current flow to the surge-absorbing diode, we strongly recommend connecting a Schottky barrier

diode (or other type of diode with a low forward voltage) in parallel with the surge-absorbing diode to construct a

bypass route for the surge current.