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Part Number: OPA1671
We are designing signal conditioning for a piezo microphone and are thus concerned with input voltage protection to clamp any high voltages generated from impact to the mic. The OPA1641 looks like an attractive choice, except there is no detail included in the data sheet about ESD protection. The 1671 data sheet does note inferior ESD ratings to the TLV6741, for example, but does not contain equivalent circuit detail, such as published with the 6741. Should I assume that some overvoltage protection is necessary if selecting this amp?
The standard IC's ESD protection includes reverse-biased ESD diodes between each I/O pin and supply pins (see below) and all parts you mentioned have them. Thus, depending on the input over-voltage level, you may have to add a series input resistor to limit the current to 10mA or less. For example, if the input voltage may be up to 10V above the supply voltage, you would need to add 1kohm in series with the input terminal (10V/1k=10mA).
Btw, if the positive supply voltage cannot sink the current, or negative supply cannot source the current, you will also need to add TVS (Zener diode) protection on supply pins as shown below to provide path for the current flow to the system ground; otherwise, the excessive input voltage may pull-up the supply pin above part's absolute maximum rated voltage resulting in over-voltage related damage.
Marek Lis, MGTSSr Application EngineerPrecision Analog - TI Tucson
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