SLVAEX7A December   2020  – January 2023 OPA2310 , OPA310 , OPA348 , OPA4310 , TLV341 , TLV341A , TLV342 , TLV342A

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Standard Op Amp ESD Protection
    1. 2.1 Standard Op Amp ESD Protection: Structure
    2. 2.2 Standard Op Amp ESD Protection: Considerations
  5. 3Op Amp ESD Protection Without Input Diodes to V+
    1. 3.1 Op Amp ESD Protection Without Input Diodes to V+: Structure
    2. 3.2 Op Amp ESD Protection Without Input Diodes to V+: Considerations
  6. 4How to Measure the ESD Structure Current of an Op Amp
  7. 5Summary
  8. 6References
  9. 7Revision History
  10.   A Measured Data for Op Amps With Alternate ESD Protection

3.1 Op Amp ESD Protection Without Input Diodes to V+: Structure

Figure 3-1 shows an example of an alternate input protection structure for the IN+ and OUT pins. The same structure is present on the IN– pin as on the IN+ pin, though the structure is not shown here for the sake of simplicity. In contrast, the output pin has diode paths to both rails. Not all of the input protection is shown here, instead, this figure shows only the portion most relevant to this application report.

GUID-20200918-CA0I-8XSZ-XRPF-Z5T8Q3TBX5RC-low.gifFigure 3-1 Current Paths for IN+ (also present for IN–) and OUT
With this type of structure, IN+ and IN- can exceed V+ without turning on a diode protection path and conducting current. For example, if V+ and V- are grounded, then a current path from the input to the supplies is prevented in the case of a positive input signal. Similarly, if V+ is left floating and V- is grounded while a positive input signal is seen, then input current to the positive supply and the possibility of back-powering the amplifier are avoided. The voltage on the inputs and supply pins still need to stay below the absolute maximum ratings mentioned in the data sheet.

Table 3-1 shows an example Absolute Maximum Ratings table from the OPAx310 High Output Current, Fast Shutdown, Low Voltage (1.5 V to 5.5 V), RRIO, 3-MHz Operational Amplifier. Unlike what was seen with a standard ESD protection structure table, where the absolute input common-mode voltages can only go 0.5 V past the supply rails, the input common-mode voltages of this alternative protection scheme do not have that limitation. There still is a limit to how far the input voltage can be taken beyond V+. Eventually, the input is driven too far and significant current begins to flow. Example test setups and sample data are provided later in this document.

Table 3-1 Absolute Maximum Ratings for the OPAx310
MINMAXUNIT
Supply voltage, VS = (V+) – (V–)

0

7V
Signal input pinsCommon-mode

voltage (1)(2)

– 0.56.0V
Differential

voltage(1)(2)

±6.0

V
Current(2)–1010mA
Output short-circuit(3)Continuous
Operating ambient temperature, TA–55150°C
Junction temperature, TJ150°C
Storage temperature, Tstg–65150°C
(1) Input pins can swing beyond (V+) as long as the pins stay with in 6.0 V. No diode structure from input pins to (V+).
(2) Input pins are diode-clamped to (V–). Input signals that 0.3 V below (V–) must be current-limited to 10 mA or less.
(3) Short-circuit to ground, one amplifier per package.

Finally, remember that the devices with this alternative ESD protection structure still start to turn on their diode protection paths if one of the input pins falls below V– minus 0.5 V. Therefore, consider what type of input signals are present while the amplifier is turned off.