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OPA2350: Input damage when powered down

Part Number: OPA2350
Other Parts Discussed in Thread: OPA350

OPA2350   If a voltage say 3V is present on the input of the op amp while the device is powered down will the device be damaged?

  • Greg,

    All pins in most IC's, including OPA350, are protected with reverse-biased ESD protection diodes to both supplies as shown below.

    Therefore, the answer to your question depends on the type of supply voltage you use.  If during the power down, the power supply, Vcc, exhibits low impedance at 0V, OPA350 as well as most other IC's will be damaged because of the very large current flowing thru ESD protection diode - see below Fig 1.  To solve the problem, you may limit the current by adding Rin resistor – see Fig 2.

    If under the power down condition, Vcc is floating (or high impedance), and there is no loading at the output, the current flowing thru ESD will be limited to the OPA350 quiescent current of 5.2mA (see Fig 3) and the op amp will not be damaged - most of the ESD protection diodes are rated for the minimum of +/-10mA current.  However, with heavy load at the output, you may have to add Rin current limiting resistor – see Fig 4.