•

CMR error

In the electrical characteristics, CMR is specified at one input common-mode voltage. To take into consideration

the variation of the input voltage offset depending on Vicm, the calculus must be done from this known point. In

the electrical characteristics all the parameters are defined at Vicm = 12 V, so it must be taken as the reference

point.

The error on output voltage Vout due to a common-mode voltage variation can be written as the equation 8:

CMR error=±Vicm−12V

CMR

*Gain

(8)

•

Noise

Figure 36 expresses the noise referred to the input of the TSC200 over the frequency:

Figure 36. Input referred noise vs. frequency

1

10

100

1k

10k

100k

1M

1

10

100

1000

10000

Frequency (Hz)

Vcc=12V

Vicm=12V

Tamb=25°C

This device shows a 1/f noise until 30 kHz frequency. Above this limit, the white noise density is 55 nV/√Hz, until

the bandwidth of the TSC200.

The noise can then be expressed in two terms, the first one related to the 1/f noise, and the second due to the

white noise. If we consider that there is no additional filter on the TSC200, and it is only bandwidth limited, it can

be considered that over 1 MHz, there is an attenuation of the noise with a first order filtering. So, the equivalent

noise bandwidth is

1MHz.π2.

The RMS value of the output noise is the integration of the spectral noise over the bandwidth of interest and can

be expressed as equation 9:

enRMS= ∫0.130000 55.10−9f30.103

2df+∫0.11000000.π255.10−92df*Gain

(9)

•

Total error

The maximum total error expected on the output of the device can be expressed as the sum of the different

sources described just above. The total output accuracy can be written as equation 10.

Vouterr=Gain*Rsense*Iload εgain+εRsense +Gain.Vio+Gain

.Vicm−12V

CMR

+noise

(10)

Iload is the current flowing into the shunt, and output noise is described by equation 9.

TSC200, TSC201, TSC202

Error calculation

DS13882 - Rev 2

page 17/34