DRV8833

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SLVSAR1E – JANUARY 2011 – REVISED JULY 2015

8.2.2.2 Motor Current Trip Point

When the voltage on pin xISEN exceeds VTRIP (0.2 V), current regulation is activated. The RISENSE resistor should

be sized to set the desired ICHOP level.

RISENSE = 0.2 V / ICHOP

(2)

To set ICHOP to 1 A, RSENSE = 0.2 V / 1 A = 0.2 Ω.

8.2.2.3 Sense Resistor

For optimal performance, it is important for the sense resistor to be:

•

Surface-mount

•

Low inductance

•

Rated for high enough power

•

Placed closely to the motor driver

The power dissipated by the sense resistor equals IRMS

2 × R. For example, if peak motor current is 3 A, RMS

motor current is 2 A, and a 0.05-

Ω sense resistor is used, the resistor will dissipate 2 A2× 0.05 Ω = 0.2 W. The

power quickly increases with higher current levels.

Resistors typically have a rated power within some ambient temperature range, along with a derated power curve

for high ambient temperatures. When a PCB is shared with other components generating heat, margin should be

added. For best practice, measure the actual sense resistor temperature in a final system, along with the power

MOSFETs, as those are often the hottest components.

Because power resistors are larger and more expensive than standard resistors, the common practice is to use

multiple standard resistors in parallel, between the sense node and ground. This distributes the current and heat

dissipation.

8.2.3 Application Curve

Figure 8. Current Regulation

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