ZHCSJ76A March 2018 – April 2019 DRV8343-Q1
PRODUCTION DATA.
To minimize DC offset and drift over temperature, a DC calibration mode is provided and enabled through the SPI register (CSA_CAL_X). This option is not available on the H/W interface device. When the calibration setting is enabled, the inputs to the amplifier are shorted and the shunt resistor is disconnected. DC calibration can be done at any time, even when the half-bridges are operating. For the best results, perform manual calibration during the switching OFF period to decrease the potential noise impact to the amplifier. Figure 35 shows a diagram of the calibration mode. When a CSA_CAL_X bit is enabled, the corresponding amplifier goes to the calibration mode.
In both the SPI and H/W device options, the CAL pin can be used to perform DC calibration to all the three amplifiers at the same time. When the CAL pin is pulled high, the inputs of all the three amplifiers are shorted and the shunt resistors are disconnected which lets the host microcontroller perform manual calibration.
In addition to the manual calibration, the DRV8343-Q1 device provides an auto calibration feature on both the SPI and H/W device versions to minimize the amplifier input offset after power up and during run time to account for temperature and device variation. Auto calibration is automatically performed on device power up for both the H/W and SPI device options. The power up auto calibration starts immediately after the VREF pin crosses the minimum operational VREF voltage. Wait 50 µs for the power up auto calibration routine to complete after the VREF pin voltage crosses the minimum VREF operational voltage. The auto calibration functions by performing a trim routine of the amplifier to minimize the amplifier input offset, after which the trim codes are stored in the device and the amplifiers are ready for normal operation. For the SPI device option, auto calibration can also be performed again during run time by enabling the CAL_MODE register setting.
NOTE
Auto calibration happens only in the bidirectional mode. If unidirectional mode is selected and auto calibration is commanded, the amplifier will switch to bidirectional mode to perform the auto calibration routine. After auto calibration routine is complete, the amplifier will revert to unidirectional mode.
For the SPI device option, auto calibration can also be performed again during run time by enabling the AUTO_CAL register setting. Auto calibration can then be commanded with the corresponding CSA_CAL_X register setting to rerun the auto calibration routine. During auto calibration all of the amplifiers will be configured for the maximum gain setting in order to improve the accuracy of the calibration routine.
For manual calibration, after writing a 1 to the CAL_CSA_X bits or taking the CAL pin high, the micro-controller needs to wait for 50 µs before performing manual calibration. This 50 µs wait time is for the auto calibration routine to complete. TI recommends that after the 50 µs expires, the micro-controller reads the outputs of the amplifiers to determine the offset and then perform the manual calibration routine.
SPI device option | H/W device option | ||
---|---|---|---|
CAL_MODE = 0b | CAL_MODE = 1b | ||
CSA_CAL_X = 1b | Manual calibration | Auto calibration | N/A |
CAL pin = High | Manual calibration | Auto calibration | Manual Calibration |