DRV8307_15 Datasheet, PDF (18/34 Pages) Texas Instruments – DRV8307 Brushless DC Motor Controller

DRV8307
SLVSCK2 – APRIL 2014
www.ti.com
An overvoltage event is recognized if the VM voltage exceeds the overvoltage threshold (VM_OVLO). Note that for
the output FETs to be protected, they must be rated for a voltage greater than the selected overvoltage
threshold.
In the event of an overvoltage, the FAULTn terminal is pulled low. The output stage is forced into asynchronous
rectification. After VM returns to a voltage below the overvoltage threshold, the FAULTn terminal is high
impedance. After a fixed 60-μs delay, synchronous rectification is re-enabled.
8.3.11.3 Motor Overcurrent Protection (OCP)
OCP is provided on each FET in addition to the current limit circuit. The OCP circuit is designed to protect the
output FETs from atypical conditions such as a short circuit between the motor outputs and each other, power, or
ground.
The OCP circuit is independent from the current limit circuitry. OCP works by monitoring the voltage drop across
the external FETs when they are enabled. If the voltage across a driven FET exceeds V_FETOCP for more than
t_FETOCP an OCP event is recognized.
In addition to monitoring the voltage across the FETs, an OCP event is triggered if the voltage applied to the
ISEN terminal exceeds the V_SENSEOCP threshold voltage.
In the event of an OCP event, FAULTn is pulled low and the motor driver is disabled.
After a fixed delay of 5 ms, the FAULTn terminal is driven inactive and the motor driver is re-enabled.
8.3.11.4 Charge Pump Failure (CPFAIL)
If the voltage generated by the high-side charge pump is too low, the high-side output FETs are not fully turned
on and excessive heating results. To protect against this, the DRV8307 device has a circuit that monitors the
charge pump voltage.
If the charge pump voltage drops below V_CPFAIL, the FAULTn terminal is pulled low and the motor driver is
disabled. After the charge pump voltage returns to a voltage above the V_CPFAIL threshold, the FAULTn terminal is
high impedance and operation of the motor driver automatically resumes.
8.3.11.5 Charge Pump Short (CPSC)
To protect against excessive power dissipation inside the DRV8307 device, a circuit monitors the charge pump
and disables it in the event of a short circuit on the PCB.
If a short circuit is detected on the charge pump, the FAULTn terminal is pulled low and the motor driver is
disabled. After a fixed period of 5 s, the FAULTn terminal is high impedance and operation of the motor driver
automatically resumes. If the short circuit condition is still present, the cycle repeats.
8.3.11.6 Rotor Lockup (RLOCK)
Circuitry in the DRV8307 device detects a locked or stalled rotor. This RLOCK can occur in the event of a
mechanical jam or excessive torque load that causes the motor to stop rotating while enabled. The rotor lock
condition is set if there are no transitions detected on the HALLOUT signal for 3 s. RLOCK can also occur if the
three Hall signals are an invalid state (all High or all Low), which can be caused by a bad wire connection. If the
BRAKE terminal goes high for longer than 3 s while the PWM clock is on DRV8307 will detect RLOCK.
If a locked rotor condition is recognized, the FAULTn terminal is pulled low and the motor driver is disabled. The
part re-enables itself after a fixed delay of 5 s.
8.3.11.7 Overtemperature (OTS)
To protect against any number of faults that could result in excessive power dissipation inside the device, the
DRV8307 device includes overtemperature protection.
Overtemperature protection activates if the temperature of the die exceeds the OTS threshold temperature
(T_TSD). If this occurs, the FAULTn terminal is pulled low and the device is disabled. The part re-enables itself
after a fixed delay of 5 s.
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