Question
Why would I select AD8237 instead of the INA333?
Answer
The AD8237 is a partial answer to the INA333, but not a complete answer. AD8237
is, by a wide margin, the lowest power zero-drift instrumentation amplifier
available from ADI. However, at almost twice the supply current of INA333, some
customers will refuse to make the switch. For now, the only answers to the 50µA
in-amp market are AD8235 and AD8236 (both not zero-drift), but look for other
products coming down the pipeline that will complete the competitive portfolio
in the INA333 zero-drift, micropower space. Though generally similar, there is
some give and take between AD8237 and INA333 specifications, so it will be
important for ADI sales, marketing, and applications to leverage its advantages
beyond the spec table against the INA333 to get design wins.
Advantages to highlight include the “hexagon plot” (Output swing vs. Input
common-mode voltage graph) on the front page of the datasheet. This behavior,
in addition to the wide input range of the AD8237, allows more flexibility in
many applications. For power-sensitive customers, this can lead to power
savings by eliminating the need for a negative power supply or common-mode
setting voltage reference, or otherwise reducing the requirement for the supply
voltage. If the customer is using an op-amp to drive the INA333 REF pin, they
can remove that op-amp in the AD8237 circuit because of the high impedance REF
pin, which may save enough power, space, and cost to generate more interest.
Another advantage is the industry-leading gain accuracy and gain drift of the
AD8237 coupled with the fact that the gain is set by two resistors. The user
can achieve unprecedented gain accuracy over temperature by using a matched
resistor network to set the gain. Even lower cost thin-film or metal-film
resistors can achieve better gain drift performance than the INA333. Other
notes: the AD8237 has better CMRR at all gains, higher bandwidth, a higher ESD
rating, better capacitive loading performance, and guaranteed bias current over
temperature.
