P =

R

(I

)

·

DS(ON)

OUT

2

DRV8814

www.ti.com

SLVSAB9D – MAY 2010 – REVISED AUGUST 2013

THERMAL INFORMATION

Thermal Protection

The DRV8814 has thermal shutdown (TSD) as described above. If the die temperature exceeds approximately

150°C, the device will be disabled until the temperature drops to a safe level.

Any tendency of the device to enter TSD is an indication of either excessive power dissipation, insufficient

heatsinking, or too high an ambient temperature.

Power Dissipation

Power dissipation in the DRV8814 is dominated by the power dissipated in the output FET resistance, or

RDS(ON). Average power dissipation of each H-bridge when running a DC motor can be roughly estimated by

Equation 2.

(2)

that at start-up and fault conditions this current is much higher than normal running current; these peak currents

and their duration also need to be taken into consideration. The factor of 2 comes from the fact that at any

instant two FETs are conducting winding current (one high-side and one low-side).

The total device dissipation will be the power dissipated in each of the two H-bridges added together.

The maximum amount of power that can be dissipated in the device is dependent on ambient temperature and

heatsinking.

be taken into consideration when sizing the heatsink.

Heatsinking

The PowerPAD™ package uses an exposed pad to remove heat from the device. For proper operation, this pad

must be thermally connected to copper on the PCB to dissipate heat. On a multi-layer PCB with a ground plane,

this can be accomplished by adding a number of vias to connect the thermal pad to the ground plane. On PCBs

without internal planes, copper area can be added on either side of the PCB to dissipate heat. If the copper area

is on the opposite side of the PCB from the device, thermal vias are used to transfer the heat between top and

bottom layers.

For details about how to design the PCB, refer to TI application report SLMA002, " PowerPAD™ Thermally

Enhanced Package" and TI application brief SLMA004, " PowerPAD™ Made Easy", available at www.ti.com.

In general, the more copper area that can be provided, the more power can be dissipated.

Copyright © 2010–2013, Texas Instruments Incorporated

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