DRV8830 Motor Driver

Device Description

The DRV8830 contains N-channel and P-channel power MOSFET’s configured as an H-bridge and can drive one DC motor or one winding of a stepper motor, as well as other loads like solenoids. The output driver can supply up to one amp DC and can operate with supply voltages from 2.75 to 6.8 volts. The internal PWM frequency is 44.5 kHz.

Voltage Regulation

The DRV8830 uses pulse width modulation (PWM) to maintain a constant motor speed and to compensate for changes in battery supply voltage. The voltage output is programmable via an I2C interface.

The voltage regulation circuit integrates the pulse width modulated output to obtain an average DC voltage value. This filtered PWM output is divided by four and compared to the output of the voltage setting (VSET DAC). If the averaged PWM output is lower than the output voltage setting (VSET DAC), the duty cycle of the PWM output is increased. If the averaged PWM output is higher than the output voltage setting (VSET DAC), the duty cycle of the PWM output is decreased. The voltage setting (VSET DAC) is set using the I2C serial interface.

If the programmed output voltage is greater than the supply voltage, the DRV8830 will operate at 100% duty cycle and the voltage regulator operation will be disabled. In this case, the device operates as a conventional “H” bridge.

Current Limit

The DRV8830 contains a current sense circuit that uses an external resistor to set the maximum output current to the motor and to protect it in the event of a stalled condition.

The motor current is determined by monitoring the voltage across the external current limit resistor and comparing it to a reference voltage of 200mV. If the current limit voltage exceeds the reference voltage for more than about 3 uS, the PWM duty cycle will be reduced to limit the current to the value set by the sense resistor.

If the overcurrent condition persists, such as in a stalled motor condition, for more than approximately 275 mS, the “FAULTn” pin will be driven low and the “FAULT” and “ILIMIT” bit in the “FAULT” register will be set, and the motor driver will continue to operate.

Setting both bits “IN1” and “IN2” in the “CONTROL” register to either zero (standby/coast) or to one (brake) will clear the fault condition. Setting the “CLEAR” bit in the “FAULT” register or removing supply power to the DRV8830 will also clear the fault condition.

Overcurrent Protection

The DRV8830 has an analog current limit circuit on each MOSFET that limits the current through the MOSFET by disconnecting the gate drive. If the analog current limit is present long enough, all the MOSFETS in the H-bridge will be disabled and the “FAULTn” pin will be driven low. Also, the “FAULT” and “OCP” bits in the “FAULT” register will be set. In this case, the motor driver will remain disabled until either the “CLEAR” bit in the fault register is written to with a one, or power to the driver is removed and then reapplied.

Overcurrent conditions are sensed independently on both high and low side devices. A short to ground, supply, or across the motor winding will result in an overcurrent shutdown.

Note: The overcurrent protection is independent of the current limit function, which is typically set to engage at a lower current level.

Other Driver Protection Circuits

The DRV8830 also has internal protection functions for over-temperature protection and under voltage lockout. Also, the “FAULT” register can be read via I2C serial interface to determine the fault source.

Thermal Shutdown

If the DRV8830 die temperature exceeds safe limits (approximately 160 DEG C), the H-bridge will be disabled and the “FAULTn” pin will be driven low, and the “FAULT” and “OTS” bits in the “FAULT” register will be set. Once the temperature has fallen to a safe level, operation will automatically resume.

Undervoltage Lockout

If at any time the voltage on the VCC pin falls below the undervoltage lockout threshold voltage, approximately 2.5VDC, the H-bridge will be disabled, the “FAULTn” pin will be driven low, and the “FAULT” and “UVLO” bits in the “FAULT” register will be set. Operation will resume when VCC rises above the “UVLO” threshold.

 

DRV8830 BREAKOUT PCB CONNECTIONS

 

DRV8830 CONNECTIONS AND H BRIDGE LOGIC

 

With a supply voltage of 5.0VDC and a voltage setting (VSET DAC) of 0.5 VDC the PWM duty cycle would be 10% (0.5VDC / 5.0VDC).

DR8830 PWM OUTPUT AT 10%

 

With a supply voltage of 5.0VDC and a voltage setting (VSET DAC) of 2.0 VDC the PWM duty cycle would be 40% (2.0VDC / 5.0VDC).

DRV8830 PWM OUTPUT AT 40%

 

Program segment to send voltage setting (VSET DAC) to DRV8830.

 

DRV8830 BREAKOUT PCB ARTWORK

 

DRV8830 BREAKOUT PCB

DRV8830 BREAKOUT PCB

 

REFERENCE: TEXAS INSTRUMENTS

 

 

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