DRV8860, DRV8860A

SLRS065E – SEPTEMBER 2013 – REVISED NOVEMBER 2015

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11.3 Thermal Consideration

The DRV8860 device has thermal shutdown (TSD) as described in the Thermal Shutdown (TSD) section. If the

die temperature exceeds approximately 150°C, the device is 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 of an ambient temperature.

11.3.1 Power Dissipation

Power dissipation in the DRV8860 device is dominated by the power dissipated in the output FET resistance,

RDS(on). Use the following equation to calculate the estimated average power dissipation of each output when

running a driving a load.

PD = RDS(on) x IO

2

where:

•

PD is the power dissipation of one channel

•

RDS(on) is the resistance of each FET

•

IO is the RMS output current being applied to each channel

(2)

IO is equal to the average current into the channel. Note that at startup, this current is much higher than normal

running current; these peak currents and their duration must be also be considered.

The total device dissipation is the power dissipated in each channel added together.

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

heatsinking.

NOTE

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

increases. This fact must be taken into consideration when sizing the heatsink.

11.3.2 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 connection can be accomplished by adding a number of vias to connect the thermal pad to the ground plane.

On PCBs without internal planes, a 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 the TI application report, PowerPAD™ Thermally Enhanced

Package (SLMA002), and the TI application brief, PowerPAD Made Easy™ (SLMA004), available at www.ti.com.

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

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