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8.1.4 Common-Mode Voltage Transients

With a small amount of additional circuitry, the INA186-Q1 can be used in circuits subject to transients that

exceed the absolute maximum voltage ratings. The most simple way to protect the inputs from negative

transients is to add resistors in series with the IN– and IN+ pins. Use resistors that are 1 kΩ or less, and limit the

current in the ESD structures to less than 5 mA. For example, using 1-kΩ resistors in series with the INA186-Q1

allows voltages as low as –5 V, while limiting the ESD current to less than 5 mA. Use the circuits shown in

Figure 8-4 and Figure 8-5 if protection from high-voltage positive or negative, common-voltage transients is

needed. When implementing these circuits, use only Zener diodes or Zener-type transient absorbers (sometimes

referred to as transzorbs); any other type of transient absorber has an unacceptable time delay. Start by adding

a pair of resistors as a working impedance for the Zener diode (see Figure 8-4). Keep these resistors as small

as possible; most often, use around 100 Ω. See Signal Conditioning for information on how larger values can

be used with an effect on gain. This circuit limits only short-term transients; therefore, many applications are

satisfied with a 100-Ω resistor along with conventional Zener diodes of the lowest acceptable power rating. This

combination uses the least amount of board space. These diodes can be found in packages as small as

SOT-523 or SOD-523.

VOUT

1.7 V to 5.5 V

IN±

IN+

OUT

RPROTECT

Bus Voltage

up to 40 V

RSENSE

Load

Capacitively

Coupled

Amplifier

INA186-Q1

REF

GND

< 1 k:

CBYPASS

0.1 µF

Figure 8-4. Transient Protection Using Dual Zener Diodes

In the event that low-power Zener diodes do not have sufficient transient absorption capability, a higher-power

transzorb must be used. The most package-efficient solution involves using a single transzorb and back-to-back

diodes between the device inputs, as shown in Figure 8-5. The most space-efficient solutions are dual, series-

connected diodes in a single SOT-523 or SOD-523 package. In either of the examples shown in Figure 8-4 and

Figure 8-5, the total board area required by the INA186-Q1 with all protective components is less than that of an

SO-8 package, and only slightly greater than that of an VSSOP-8 package.

VOUT

1.7 V to 5.5 V

IN±

IN+

OUT

RPROTECT

Bus Voltage

up to 40 V

RSENSE

Load

Capacitively

Coupled

Amplifier

INA186-Q1

REF

GND

< 1 k:

Transorb

CBYPASS

0.1 µF

Figure 8-5. Transient Protection Using a Single Transzorb and Input Clamps

For more information, see the Current Shunt Monitor With Transient Robustness reference design.

www.ti.com

INA186-Q1

SBOS386B – MAY 2019 – REVISED MARCH 2022

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