Data Sheet

P = HS - R I LS - R I

TOT DS(ON) OUT(RMS) DS(ON) OUT(RMS)

( ) + ( )· ·

2 2

DRV8834

www.ti.com

SLVSB19D –FEBRUARY 2012–REVISED MARCH 2015

Thermal Considerations (continued)

11.3.2 Thermal Protection

The DRV8834 has thermal shutdown (TSD) as described above. If the die temperature exceeds approximately

160°C, the device will be disabled until the temperature drops to a safe level.

Any tendency of the device to enter thermal shutdown is an indication of either excessive power dissipation,

insufficient heatsinking, or too high an ambient temperature.

11.3.3 Power Dissipation

Power dissipation in the DRV8834 is dominated by the DC power dissipated in the output FET resistance, or

DS(ON)

. There is additional power dissipated due to PWM switching losses, which are dependent on PWM

frequency, rise and fall times, and VM supply voltages. These switching losses are typically on the order of 10%

to 20% of the DC power dissipation.

The DC power dissipation of one H-bridge can be roughly estimated by Equation 5.

(5)

where P

TOT

is the total power dissipation, HS - R

DS(ON)

is the resistance of the high side FET, LS - R

DS(ON)

is the

resistance of the low side FET, and I

OUT(RMS)

is the RMS output current being applied to the motor.

DS(ON)

increases with temperature, so as the device heats, the power dissipation increases. This must be taken

into consideration when sizing the heatsink.

11.3.4 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, PowerPAD™ Thermally Enhanced

Package(SLMA002), and 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.

Product Folder Links: DRV8834