ULQ2003A: R

= 2.7 k

B

W

ULQ2004A: R

= 10.5 k

B

W

7.2 kW

3 kW

R

B

ULQ2003A-Q1, ULQ2004A-Q1

SGLS148E – DECEMBER 2002 – REVISED DECEMBER 2015

www.ti.com

Functional Block Diagram (continued)

A.

All resistor values shown are nominal.

B.

The collector-emitter diode is a parasitic structure and should not be used to conduct current. If the collector(s) go

below ground an external Schottky diode should be added to clamp negative undershoots.

Figure 14. Schematics (Each Darlington Pair)

8.3 Feature Description

Each channel of the ULQ200xA-Q1 devices consist of Darlington connected NPN transistors. This connection

creates the effect of a single transistor with a very high-current gain (

β2). This can be as high as 10,000 A/A at

certain currents. 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-k

Ω or 10.5-kΩ resistor connected between the

input and base of the predriver Darlington NPN. The 7.2-k

Ω and 3-kΩ resistors connected between the base and

emitter of each respective NPN act as pulldowns and suppress the amount of leakage that may occur from the

input.

The diodes connected between the output and COM pin is 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 reversed biased. If these diodes are

forward biased, internal parasitic NPN transistors will draw (a nearly equal) current from other (nearby) device

pins.

8.4 Device Functional Modes

8.4.1 Inductive Load Drive

When the COM pin is tied to the coil supply voltage, ULQ200xA-Q1 devices are able to drive inductive loads and

suppress the kick-back voltage through the internal free-wheeling diodes.

8.4.2 Resistive Load Drive

When driving a resistive load, a pullup resistor is needed in order for the ULQ200xA-Q1 devices to sink current

and for there to be a logic high level. The COM pin can be left floating for these applications.

10

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