INA293

Part: INA293, Texas Instruments

Type: Ultra-Precision Current Sense Amplifier

Description: The INA293 is an ultra-precision current sense amplifier capable of measuring voltage drops across shunt resistors in a wide common-mode range of –4V to 110V, featuring 1.3MHz bandwidth, 160dB DC CMRR, and multiple fixed gain options.

Operating Conditions:

• Supply voltage: 2.7–20 V
• Operating temperature: -40 to +125 °C
• Common-mode input range: -4 V to +110 V

Absolute Maximum Ratings:

• Max supply voltage: 22 V
• Max junction/storage temperature: 150 °C

Key Specs:

• Common-mode input range (VCM): -4 V to 110 V (TA = -40°C to +125°C)
• DC Common-mode rejection ratio (CMRR): 160 dB (typ)
• AC Common-mode rejection ratio (CMRR): 85 dB (typ, at 50 kHz)
• Offset voltage (Vos): ±15 μV (typ)
• Gain error: ±0.15% (max)
• Gain drift: ±10 ppm/°C (max)
• Bandwidth: 1.3 MHz (typ)
• Slew rate: 2.5 V/μs (typ)
• Quiescent current: 1.5 mA (typ)

Features:

• Wide common-mode voltage: -4 V to +110 V (operating), -20 V to +120 V (withstand)
• Excellent common-mode rejection ratio (CMRR): 160dB DC, 85dB AC (50kHz)
• High accuracy: ±0.15% max gain error, ±10ppm/°C max gain drift, ±15μV typ offset voltage, ±0.05μV/°C typ offset drift
• Available fixed gains: 20V/V, 50V/V, 100V/V, 200V/V, 500V/V
• High bandwidth: 1.3 MHz
• Slew rate: 2.5 V/μs
• Low quiescent current: 1.5mA

Applications:

• Active Antenna Systems (mMIMO (AAS))
• Macro Remote Radio Units (RRU)
• 48V Rack Servers
• 48V Commercial Network and Server Power Supplies (PSU)
• 48V Battery Management Systems (BMS)

Package:

• SOT-23 (5 pins)

图 5-1. INA293A: DBV Package 5-Pin SOT-23 Top View

图 5-2. INA293B: DBV Package 5-Pin SOT-23 Top View

表 5-1. Pin Functions

• NAME
• GND
• OUT
• Vs
• IN+
• IN–

at TA = 25 °C, VS = 5 V, VSENSE = VIN+ - VIN- = 0.5 V / Gain, VCM = VIN- = 48 V (unless otherwise noted)

over operating free-air temperature range (unless otherwise noted)(1)

⁽¹⁾ Stresses beyond those listed under Absolute Maximum Rating may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Condition. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) VIN+ and VIN– are the voltages at the IN+ and IN– pins, respectively.

over operating free-air temperature range (unless otherwise noted)

⁽¹⁾ For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report.

6.5 Electrical Characteristics

at TA = 25 °C, VS = 5 V, VSENSE = VIN+ - VIN- = 0.5 V / Gain, VCM = VIN- = 48 V (unless otherwise noted)

The INA293 amplifies the voltage developed across a current-sensing resistor as current flows through the resistor to the load. The wide input common-mode voltage range and high common-mode rejection of the INA293 make it usable over a wide range of voltage rails while still maintaining an accurate current measurement.

8.1.1 R_SENSE and Device Gain Selection

The accuracy of any current-sense amplifier is maximized by choosing the current-sense resistor to be as large as possible. A large sense resistor maximizes the differential input signal for a given amount of current flow and reduces the error contribution of the offset voltage. However, there are practical limits as to how large the current-sense resistor can be in a given application because of the resistor size and maximum allowable power dissipation. 方程式 1 gives the maximum value for the current-sense resistor for a given power dissipation budget:

$R_SENSE < frac{PD_MAX}{I_MAX²} tag{1}$

where:

• PD_MAX is the maximum allowable power dissipation in R_SENSE.
• I_MAX is the maximum current that will flow through R_SENSE.

An additional limitation on the size of the current-sense resistor and device gain is due to the power-supply voltage, V_S, and device swing-to-rail limitations. To make sure that the current-sense signal is properly passed to the output, both positive and negative output swing limitations must be examined. 方程式 2 provides the maximum values of R_SENSE and GAIN to keep the device from exceeding the positive swing limitation.

$I_MAX × R_SENSE × GAIN < V_SP$ (2)

where:

• I_MAX is the maximum current that will flow through R_SENSE.
• GAIN is the gain of the current-sense amplifier.
• V_SP is the positive output swing as specified in the data sheet.

To avoid positive output swing limitations when selecting the value of R_SENSE, there is always a trade-off between the value of the sense resistor and the gain of the device under consideration. If the sense resistor selected for the maximum power dissipation is too large, then it is possible to select a lower-gain device in order to avoid positive swing limitations.

The negative swing limitation places a limit on how small the sense resistor value can be for a given application. 方程式 3 provides the limit on the minimum value of the sense resistor.

$I_MIN × R_SENSE × GAIN > V_SN(3)

where:

• I_MIN is the minimum current that will flow through R_SENSE.
• GAIN is the gain of the current-sense amplifier.

• VSN is the negative output swing of the device.

表 8-1 shows an example of the different results obtained from using five different gain versions of the INA293. From the table data, the highest gain device allows a smaller current-shunt resistor and decreased power dissipation in the element.

(1) Design example with 10-A full-scale current with maximum output voltage set to 5 V.

8.1.2 Input Filtering

备注

Input filters are not required for accurate measurements using the INA293, and use of filters in this location is not recommended. If filter components are used on the input of the amplifier, follow the guidelines in this section to minimize the effects on performance.

Based strictly on user design requirements, external filtering of the current signal may be desired. The initial location that can be considered for the filter is at the output of the current sense amplifier. Although placing the filter at the output satisfies the filtering requirements, this location changes the low output impedance measured by any circuitry connected to the output voltage pin. The other location for filter placement is at the current sense amplifier input pins. This location satisfies the filtering requirement also, however the components must be carefully selected to minimally impact device performance. 图 8-1 shows a filter placed at the input pins.

图 8-1. Filter at Input Pins

External series resistance provides a source of additional measurement error, so keep the value of these series resistors to 10 Ω or less to reduce loss of accuracy. The internal bias network shown in 图 8-1 creates a mismatch in input bias currents (see 图 6-15, 图 6-16 and 图 6-17) when a differential voltage is applied between the input pins. If additional external series filter resistors are added to the circuit, a mismatch is created in the voltage drop across the filter resistors. This voltage is a differential error voltage in the shunt resistor voltage. In addition to the absolute resistor value, mismatch resulting from resistor tolerance can significantly impact the error because this value is calculated based on the actual measured resistance.

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The measurement error expected from the additional external filter resistors can be calculated using 方程式 4, where the gain error factor is calculated using 方程式 5.

Gain Error (%) =100 - (100 × Gain Error Factor)$ (4)

The gain error factor, shown in 方程式 4, can be calculated to determine the gain error introduced by the additional external series resistance. 方程式 4 calculates the deviation of the shunt voltage, resulting from the attenuation and imbalance created by the added external filter resistance. 表 8-2 provides the gain error factor and gain error for several resistor values.

Gain Error Factor = $frac{R_B × R1}{(R_B × R1) + (R_B × R_IN) + (2 × R_IN × R1)}$ (5)

Where:

• RIN is the external filter resistance value.
• R1 is the INA293 input resistance value specified in 表 7-1.
• RB in the internal bias resistance, which is 6600 Ω ± 20%.

表 **8-2. Example Gain Error Factor and Gain Error for 10-**Ω External Filter Input Resistors