Automotive Hall current sensor is 1% over life and includes MCU
“MLX91230 guarantees this accuracy not only for thermal drift but also lifetime drift and linearity errors,” according to the company.
The 8pin SOIC device is AEC-Q100 and ASIL compliant, supporting system integration up to ISO 26262 ASIL D functional safety requirements.
Current measurement accuracy is 0.5% over -40 to 125℃, and 1% lifetime drift over everything. Output is over LIN or UART signal – wake on LIN or UART is possible and there is an internal wake timer.
Along with current measurement is a over-current detector that trips in under 500µs – it is actually a magnetic threshold detector, and can be set between ±100 and ±650mT. This output shares pins with the UART Tx pad or the LIN interface pad, so one of them has to be sacrificed to use it.
The over-current detector output can be a binary signal or a PWM that alters ratio abruptly on over-load. According to the company, it is suitable for connection to a vehicle’s pyro-fuse driver.
There is also a second galvanically-connected current sensing channel, designed to work with an external current sense resistor in the 0V rail.
On top of this, the IC also measures voltage and temperature.
There are three voltage-sense options, all operating through the same pad: direct (300mV to 1.1V), ‘LVbat’ (12V nom, 4.5 to 18V) and ‘HVbat’ (24V and 48V nom, 20 to 60V). An external divider and insulation can be added to connect to 400 and 800V batteries.
For temperature there is an internal (PTAT) sensor, plus an interface for an external NTC thermistor is also integrated, but the thermistor connection is not brought out to an external pin in the 8pin SOIC version currently available.
The IC need a supply at 5V, or a direct connection to the 12V battery rail (36Vmax).
Some of the features and compensation is implemented by an internal 16bit microcontroller, which can be re-programmed to account for external system errors.
“The MCU enables automatic gain control to cover higher dynamic ranges, and its on-board flash memory supports custom software, compensation of system imperfections and low power modes,” said Melexis. Regarding external compensation “examples are ferromagnetic saturation onset, non-linearities and hysteresis compensation”.
Alongside the MCU is 32kbyte flash, 128byte configuration flash, 20kbyteROM, 2kbyte ram and 512byte eeprom.
There is a lot going on in this IC – more to each function than is mentioned above. See the MLX91230 data sheet for more detail, or start at the product page here.
“This digital device provides an accurate and reliable monitoring solution while also meeting the highest functional safety requirements,” said Melexis. “For battery installations, it supports state of charge, battery state-of-health and state-of-function in both low voltage and high voltage systems – ideal for battery management systems, battery disconnect units and battery junction boxes.”