DRV8816 Datasheet, PDF (10/17 Pages) Texas Instruments – DMOS DUAL 1/2-H-BRIDGE MOTOR DRIVERS

DRV8816
SLRS063 – SEPTEMBER 2013
www.ti.com
OVERCURRENT PROTECTION (OCP)
The current flowing through the high-side and low-side drivers is monitored to ensure that the motor lead is not
shorted to supply or ground. If a short is detected, all FETs in the H-bridge will be disabled, nFAULT is driven
low, and a t_OCP fault timer is started. After this period, t_OCP, the device is then allowed to follow the input
commands and another turn-on is attempted (nFAULT becomes high again during this attempt). If there is still a
fault condition, the cycle repeats. If after t_OCP expires it is determined the short condition is not present, normal
operation resumes and nFAULT is released.
OVERTEMPERATURE WARNING (OTW)
If the die temperature increases past the thermal warning threshold the nFAULT pin will be driven low. Once the
die temperature has fallen below the hysteresis level, the nFAULT pin will be released. If the die temperature
continues to increase, the device will enter over temperature shutdown as described below.
OVERTEMPERATURE SHUTDOWN (OTS)
If the die temperature exceeds safe limits, all FETs in the H-bridge will be disabled and the charge pump will be
shut down. Once the die temperature has fallen to a safe level operation will automatically resume.
THERMAL INFORMATION
Thermal Protection
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 thermal shutdown is an indication of either excessive power
dissipation, insufficient heatsinking, or too high an ambient temperature.
Power Dissipation
Power dissipation in the DRV8816 is dominated by the power dissipated in the output FET resistance, or R_DS(ON).
Average power dissipation can be roughly estimated by:
P_TOT = R_D(SON) ´ (I_OUT(RMS))²
(1)
where P_TOT is the total power dissipation, R_D(SON) is the resistance of the HS plus LS FETS, and I_OUT(RMS) is the
RMS output current being applied to each winding. I_OUT(RMS) is equal to approximately 0.7× the full-scale output
current setting.
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.
PCB LAYOUT
Ground
A ground power plane should be located as close to DRV8816 as possible. The copper ground plane directly
under the PowerPAD package makes a good location. This pad can then be connected to ground for this
purpose.
Layout Considerations
The printed circuit board (PCB) should use a heavy ground plane. For optimum electrical and thermal
performance, the DRV8816 must be soldered directly onto the board. On the underside of the DRV8816 is a
PowerPAD package, which provides a path for enhanced thermal dissipation. The thermal pad should be
soldered directly to an exposed surface on the PCB. Thermal vias are used to transfer heat to other layers of the
PCB.
The load supply pin, VBB, should be decoupled with an electrolytic capacitor (typically 100 μF) in parallel with a
ceramic capacitor placed as close as possible to the device. The ceramic capacitors between VCP and VBB,
connected to VREG, and between CP1 and CP2 should be as close to the pins of the device as possible, in
order to minimize lead inductance.
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