DRV8313 datasheet(9/19 Pages) TI

9 / 19 page

DS(on)

OUT

)

DRV8313

www.ti.com

SLVSBA5A – OCTOBER 2012 – REVISED NOVEMBER 2012

UNDERVOLTAGE LOCKOUT (UVLO)

If at any time the voltage on the VM pins falls below the undervoltage-lockout threshold voltage, the device

disables all outputs, resets internal logic, and drives the nFAULT pin low. Operation resumes when VM rises

above the UVLO threshold.

THERMAL INFORMATION

Thermal Protection

The DRV8313 has thermal shutdown (TSD) as previously described. A die temperature in excess of

approximately 150°C disables the device until the temperature drops to a safe level.

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

heatsinking, or too high an ambient temperature.

Power Dissipation

The power dissipated in the output FET resistance, or rDS(on) dominates power dissipation in the DRV8313. A

rough estimate of average power dissipation of each half-H-bridge when running a static load is:

(1)

where P is the power dissipation of one H-bridge, rDS(on) is the resistance of each FET, and IOUT 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; remember to take these peak currents and their duration into consideration.

The total device dissipation is the power dissipated in each of the three half-H-bridges added together.

The maximum amount of power that the device can dissipate depends on ambient temperature and heatsinking.

Note that rDS(on) increases with temperature, so as the device heats, the power dissipation increases. Take this

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,

add a number of vias to connect the thermal pad to the ground plane to accomplish this. On PCBs without

internal planes, add copper area on either side of the PCB to dissipate heat. If the copper area is on the opposite

side of the PCB from the device, use thermal vias to transfer the heat between the top and bottom layers.

For details about how to design the PCB, see TI Application Report SLMA002, PowerPAD Thermally Enhanced

Package and TI Application Brief SLMA004, PowerPAD Made Easy, available at www.ti.com.

In general, providing more copper area allows the dissipation of more power.

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DRV8313 Datasheet(PDF) 9 Page - Texas Instruments