1% current sense amplifier ICs for high or low-side measurement

They work with external shunt resistors, and there are two basic types: one (BD1423xFVJ-C) that can sense across the common-mode range of -14 to +80V and runs from 2.7 to 18V, and the other (BD1422xG-C) that can sense across -14 to +40V and runs from 2.7 to 5.5V.

In each case, there is a choice of voltage gain: 25, 50 or 100V/V.

The above is true with one exception: the lowest gain 80V type has a gain of 20 (not 25) and can only be powered up to 5.5V, not 18V – there is a table below that summarises this detail.

80V input types come in 3 x 4.9mm TSSOP-B8J packaging and are intended for things like 48V dc-dc converters, auxiliary batteries and electric compressors.

40V input types come in 2.9 x 2.8mm SSOP6 package, and are intended for current monitoring and over-current protection in 5V/12V power supply networks used in body and drivetrain domains.

Input current is around ±1μA.

“In recent years, alongside conventional 5V/12V power supplies, the automotive market has seen a growing adoption of 48V systems fuelled by the rising popularity of electric vehicles,” said Rohm. “As vehicle functionality becomes more advanced, the need for precise monitoring increases.”

Inside is a front-end chopper amplifier and a back-end auto-zero amplifier (see diagram).

The internal gain-setting resistors are match for ±1% sensing. “Furthermore, current detection accuracy is maintained even when an external RC filter circuit added for noise suppression,” said Rohm. 14V negative voltage tolerance supports back electromotive force, reverse connection and negative voltage input.”

As well as the input voltage difference, 40V parts include a pair of resistors (see diagram) that can be used to set a reference to half of the supply voltage. These have to be supplied externally for the 80V types.

Operation is across -40 to +125°C.

Data sheets:
40V BD1422xG-C
80V BD1423xFVJ-C

In May, Rhopoint began stocking 1W 6.3 x 3.2mm current sensing resistances between 0.01Ω and 1Ω