The FB pin in INA790x has associated bias current, which can add to error when large values of adjustable gain

resistor, RFB1, is used. Alternatively, very low values of adjustable gain resistors load the output of the sense

amplifier limiting the capability of the sense amplifier to get close to the supply rail. Keeping the sum of external

resistors RFB1 and RFB2 between 10kΩ and 40kΩ is recommended when external adjustable gain is higher than

1. Table 6-1 shows recommended values of external gain resistors for the most common gains.

Table 6-1. Recommended Values of External Resistors Setting Adjustable Gain

External Adjustable Gain

RFB1

RFB2

Total Gain (G)

1

0Ω (short)

Open

20mV/A

2

20kΩ

20kΩ

40mV/A

4

30kΩ

10kΩ

80mV/A

5

20kΩ

5kΩ

100mV/A

6.4.2.1 Adjustable Unity Gain

Figure 6-9 shows adjustable gain set to unity gain or 1. In this configuration OUT is connected to FB without any

external resistor. This unity gain sets INA790x to default minimum gain of 20mV/A. Equation 3 can be used to

calculate the total gain of the system. The REF pin is connected to external reference based on needed output

voltage setting as described in Adjusting the Output With the Reference Pin.

PWM

Rejection

Shunt

Resistor

OUT

FB

REF

VS

GND

IS+

IS-

2.7V to 5.5V

+

–

External

Reference

Shunt Current

Alert

LOAD

GND

Rpullup

+

–

0.1 F

IN-

IN+

Figure 6-9. Adjustable Unity Gain Setting

6.4.3 Thermal Alert Function

The INA790x has thermal Alert function that provides an alert when internal shunt temperature reaches 160°C.

The power dissipation as a result of internal shunt current causes the temperature to rise inside the package.

Extended time at temperature higher than 150°C can cause permanent shift in device specification. Thermal

alert function can be used to keep the temperature of INA790x below 150°C. Figure 6-10 shows a circuit where

Rpullup resistor is tied between open-drain Alert pin and the supply pin. When temperature of the INA790x

reaches 160°C, the open-drain FET pulls Alert pin to the ground asserting thermal alert.

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INA790A, INA790B

SBOSAA6B – MAY 2024 – REVISED JULY 2025

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