DRV8804_15 Datasheet, PDF (9/21 Pages) Texas Instruments – QUAD SERIAL INTERFACE LOW-SIDE DRIVER IC

DRV8804
www.ti.com
THERMAL INFORMATION
SLVSAW4E – JULY 2011 – REVISED JANUARY 2014
Thermal Protection
The DRV8804 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 DRV8804 is dominated by the power dissipated in the output FET resistance, or
RDS(ON). Average power dissipation of each FET when running a static load can be roughly estimated by
Equation 1:
P = R_DS(ON) · (I_OUT)²
(1)
where P is the power dissipation of one FET, R_DS(ON) is the resistance of each FET, and I_OUT is equal to the
average current drawn by the load. Note 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. When
driving more than one load simultaneously, the power in all active output stages must be summed.
The maximum amount of power that can be dissipated in the device is dependent on ambient temperature and
heatsinking.
Note that R_DS(ON) increases with temperature, so as the device heats, the power dissipation increases. This must
be taken into consideration when sizing the heatsink.
Heatsinking
The DRV8804DW package uses a standard SOIC outline, but has the center pins internally fused to the die pad
in order to more efficiently remove heat from the device. The two center leads on each side of the package
should be connected together to as large a copper area on the PCB as is possible to remove heat from the
device. 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.
In general, the more copper area that can be provided, the more power can be dissipated.
The DRV8804PWP package uses an HTSSOP package with an exposed PowerPAD™. 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.
Copyright © 2011–2014, Texas Instruments Incorporated
Product Folder Links: DRV8804
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