26V current sensor in 2.9 x 2.8mm has 1% error

Author: EIS Release Date: Mar 16, 2023

Rohm has announced a high-side current sensor with a -0.2 to +26V input common-mode range and ±1.0% maximum gain error.

 

Rohm BD14210G-LA current sense amplifier

Packaged in a 2.9 x 2.8 x 1.25mm SSOP6, BD14210G-LA senses voltage across an external high-side resistor and transfers this to a voltage relative to the 0V rail with a fixed gain of 20. Max offset is ±0.6mV (refered to the input).

 

Rohm BD14210G-LA eval board

 

Inside it is a two-stage design, with a chopping amplifier front end (switches missing from diagram) followed by a differential amplifier. With two stages, Rohm claims that the gain of the differential stage is not affected by adding an RRC input noise filter, with a pair of 10Ω resistors, for example.

 

The voltage at the output is with respect to a voltage supplied to its reference input, supplied by a potentiometer in Rohm’s typical application circuit above.

 

Electronics Weekly asked how the external potentiometer in the diagram interacts with the internal differential amplifier resistors – and Rohm has responded with this document, which suggests only the voltage offset, and not the gain of the differential amplifier is affected by the potentiometer  – does anyone disagree with this (comment below) – maybe CMRR will be compromised?

 

The IC needs its own 2.7 to 5.5V power supply, from which it typically draws 170μA, and it operates over -40 to +125°C. The ±1% worst case error is right across this temperature range, and over outputs between 500mV and Vdd-500mV.

 

This is the first of a family (see table) of high-side current sensing ICs with gains up to 200. There will also be dual versions in 3 x 4.9 x 1.1mm TSSOP-B8J packaging.