米6体育平台手机版

ZHCSR64C december 2022 – may 2023 INA351

PRODUCTION DATA

封装选项

机械数据 (封装 | 引脚)

DSG|8
- MPDS308C
RUG|10
- MPQF216A

散热焊盘机械数据 (封装 | 引脚)

DSG|8
- QFND141I

订购信息

9.2.1.2 Detailed Design Procedure

This section provides basic calculations to lay out the instrumentation amplifier with respect to the given design requirements.

One of the key considerations in resistive-bridge sensors is the common-mode voltage, V_CM. If the bridge is balanced (no pressure, thus no voltage change), V_CM(zero) is half of the bridge excitation (V_EXT). In this example V_{CM (zero)} is 2.5 V. For the maximum pressure of 12 psi, the bridge common-mode voltage, V_CM(MAX), is calculated by:

Equation 5.

V_{C M (M A X)} = \frac{V_{D I F F}}{2} + V_{C M (z e r o)}

where

Equation 6.

V_{D I F F} = S_{M A X} \times V_{E X T} \times P_{M A X} = 2.5 \frac{m V}{V \times p s i} \times 5 V \times 12 p s i = 150 m V

Thus, the maximum common-mode voltage applied results in:

Equation 7.

V_{C M (M A X)} = \frac{150 m V}{2} + 2.5 V = 2.575 V

Similarly, the minimum common-mode voltage can be calculated as,

Equation 8.

V_{C M (M I N)} = \frac{- 150 m V}{2} + 2.5 V = 2.425 V

The next step is to calculate the gain required for the given maximum sensor output voltage span, V_DIFF, in respect to the required V_OUT, which is the full-scale range of the ADC.

The following equation calculates the gain value using the maximum input voltage and the required output voltage:

Equation 9.

G = \frac{V_{O U T}}{V_{D I F F (M A X)}} = \frac{3.0 V}{150 m V} = 20 V / V

Considering, INA351 is a selectable gain INA with gain options of 10, 20, 30, 50, the INA351ABS with GS tied high enables G = 20 maintaining the maximum output signal swing for the ADC.

Next, let us make sure that the INA351 can operate within this range checking the Input Common-Mode Voltage vs Output Voltage curves in the Typical Characteristics section. The relevant figure is also in this section for convenience. Looking at Figure 9-70, we can confirm that a output signal swing of 3 V is supported for the input signal swing between 2.425 V and 2.575 V, thus making sure of the linear operation.

V_S = 5.5 V

G = 10, 20, 30, 50

V_REF = 0 V

Figure 9-5 Input Common-Mode Voltage vs Output Voltage (High CMRR Region)

An additional series resistor in the Wheatstone bridge string (R1) may or may not be required, and can be decided based on the intended output voltage swing for a particular combination of supply voltage, reference voltage and the selected gain for an input common mode voltage range. R1 helps adjust the input common-mode voltage range, and thus can help accommodate the intended output voltage swing. In this particular example, it is not required and can be shorted out.