SBOA518 January   2022 TMCS1100 , TMCS1100-Q1 , TMCS1101 , TMCS1101-Q1 , TMCS1107 , TMCS1107-Q1 , TMCS1108 , TMCS1108-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Device Operation
  4. 3Grounding
  5. 4Measurement Range
    1. 4.1 Swing Limitations
    2. 4.2 Noise Limitations
  6. 5External Fields
    1. 5.1 Earth's Magnetic Field
    2. 5.2 Conduction Paths
    3. 5.3 Additional Magnetic Components
  7. 6External Field Mitigation
    1. 6.1 Shielding
    2. 6.2 Calibration
  8. 7Summary

4.1 Swing Limitations

Neglecting the influences of external error sources, which varies from design and operating environment, it is important to note that there are two bounds of output to examine for the device: the swing limit, and the linear operating range.

The first boundaries to consider are the swing limitations of the device. TMCS1101 Data Sheet: Swing Specifications shows the swing limitations, and demonstrates the maximum voltages that can actually be output by the device before entering a saturated condition. These bounds of output voltage for each sensing direction are determined from Equation 2 and Equation 3. The results of these equations give the range that the device is capable of measuring for the chosen operating conditions of VREF and Vs.

Equation 2. I Forward ≤ Swing_to_V S , max − V REF Sensitivity
Equation 3. I Reverse ≥ Swing_to_GND , max - V REF Sensitivity
Table 4-1 TMCS1101 Data Sheet: Swing Specifications
PARAMETERS TEST CONDITIONS MIN TYP MAX UNIT
VOLTAGE OUTPUT
Swing to VS power-supply rail RL = 10 kΩ to GND, TA= –40°C to +125°C VS – 0.02 VS – 0.1 V
Swing to GND, current driven RL = 10 kΩ to GND, TA= –40°C to +125°C VGND + 5 VGND + 10 mV

The second boundary, which is a smaller subset located within the swing conditions, is the linear operating range, given for each device in TMCS1101 Data Sheet: Linear Operating Region.

Table 4-2 TMCS1101 Data Sheet: Linear Operating Region
PRODUCT SENSITIVITY ZERO CURRENT OUTPUT VOLTAGE, IIN LINEAR MEASUREMENT RANGE
ΔVOUT / ΔIIN+, IN– VOUT,0A VS = 5 V VS = 3.3 V
TMCS1101A1B-Q1 50 mV/A 0.5 × VS ±46 A ±29 A
TMCS1101A2B-Q1 100 mV/A ±23 A ±14.5 A
TMCS1101A3B-Q1 200 mV/A ±11.5 A ±7.25 A
TMCS1101A4B-Q1 400 mV/A ±5.75 A –
TMCS1101A1U-Q1 50 mV/A 0.1 × VS –9 A → 86 A –5.6 A → 55.4A
TMCS1101A2U-Q1 100 mV/A –4.5 A → 43A –2.8 A → 27.7 A
TMCS1101A3U-Q1 200 mV/A –2.25 A → 21.5 A –1.4 A → 13.85 A
TMCS1101A4U-Q1 400 mV/A –1.12 A → 10.75 A –

This smaller subset is the range to which the sensitivity error of the device has been applied, and is ensured to operate within the data sheet specification. Care must also be taken to ensure that current levels remain below both allowable continuous DC/RMS and transient peak current safe operating areas to not exceed device thermal limits. More information on this can be found in the Safe Operating Area section of the data sheet. In short, this shows that while the TMCS1101 may be configured to work to the voltage outputs of the swing limitation, the linearity may be slightly worse at the areas of output that fall outside the linear operating range. For optimal performance, ensure that the design is kept to within the linear operating region.

See the Under the Hood: Output Swing Limitations of Current Sense Amplifiers application report for reasons behind these limitations.