2

TOT

DS(on )

(RMS)

P

2 R

IOUT

=

´

´

DRV8828

SLVSA11G – OCTOBER 2009 – REVISED NOVEMBER 2015

www.ti.com

10.3 Power Dissipation

Power dissipation in the DRV8828 is dominated by the power dissipated in the output FET resistance, or

RDS(on). Average power dissipation when running a brushed DC motor can be roughly estimated by Equation 3.

(3)

Where:

•

PTOT is the total power dissipation

•

RDS(on) is the resistance of each FET (high-side and low-side)

•

IOUT(RMS) is the RMS output current being applied to the motor

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

heatsinking. RDS(on) increases with temperature, so as the device heats, the power dissipation increases. This

must be taken into consideration when sizing the heatsink.

10.4 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.

10.4.1 Thermal Information

The DRV8828 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.

18

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