Figure 35. Input current

Vicm

lib-

lib+

+

-

Gnd

Isource

Iload

From a calculation approach when working with a Vicm over 2.5 V, if Isource is considered to be known rather than

the Iload, in this case the input bias current should be taken into consideration.

Figure 35 express also the fact that the TSC21x cannot measure current in the same order than input bias current

(several hundreds of µA).

•

Example

Let’s take an example to get a better understanding of the maximum total error that can happen on the output of

the TSC213.

Use case:

- Vcc = 5 V

- Vicm = 24 V

- Vocm = 2.5 V

- Temperature = 25 °C

- Iload = 5 A

- Shunt 5 mΩ with 1% accuracy

Theoretically the expected output voltage should be Vout = Rshunt * Iload * 50 + Vref = 3.75 V.

From the above equations let’s detail all the error terms by using the maximum value of the electrical

characteristic (when available), in order to express as much as possible, the worst case condition. The % error on

output of the following table is expressed in reference to Vout – Vref, so in this typical example: 1.25 V.

Table 6. Gain error

Error source

Calculus

Output voltage error

% error on

output

Gain error

50*5.10−3*5*1%

12.5 mV

1%

Vio error

50*100µV

5 mV

0.4%

CMRR error

50*24V−12V

1010020

6 mV

0.5%

Noise

50*38nVHz 100kHz*π2−0.1Hz

0.75 mVRMS

0.2%

Total

18.1 mV

+0.75 mVRMS

2.1%

1. The percentage is based on voltage peak value and is 3 times RMS value.

TSC210, TSC211, TSC212, TSC213, TSC214, TSC215

Error calculation

DS13237 - Rev 6

page 18/38