Even if the TSC213 is a zero-drift current sensor allowing small shunt use, at first order the input offset voltage

(Vio) and the input bias current (Iib) should be put in with regards to the differential voltage in the shunt resistance.

Figure 34 shows the trade-off between the accuracy at minimum current and power dissipation.

Figure 34. Shunt resistor value trade-off (TSC213)

0

1

2

3

4

5

6

7

8

9

10

11

12

0

2

4

6

8

10

12

14

0.0

0.4

0.8

1.2

Shunt resistor value

(m

W)

Shunt resistor vs input error

at minimumcurrent (1 A)

Shunt resistor vs power dissipation

at maximumcurrent (10A)

Vcc = 5 V, Vicm = 12V

Increasing the shunt resistor values improves current accuracy, but also increases power dissipation!

•

If power dissipation in the shunt is the key point, RSense should be chosen as

Rsense≤PmaxImax²

and then chose the right TSC21x gain products. For example, for high current to sense, it is better to use the

TSC212 offering a gain of 1000, allowing to use a smaller shunt and so limited power losses. But accuracy

can be lower.

•

Or choose the TSC21x gain product available on the shelf, and then size the shunt resistor value

accordingly.

6.5

Input offset voltage drift overtemperature

The maximum input offset voltage drift overtemperature is defined as the offset variation related to the offset value

measured at 25 °C. The signal chain accuracy at 25 °C can be compensated during production at application

level. The maximum input voltage drift overtemperature enables the system designer to anticipate the effect of

temperature variations.

The maximum input voltage drift overtemperature is computed using equation 2:

ΔVioΔT=maxVioT −Vio25°C

T−25°C

(2)

where T = - 40 °C and 125 °C

The TSC21x datasheet maximum value is guaranteed by measurements on a representative sample size

ensuring a Cpk (process capability index) greater than 1.3.

6.6

Error calculation

The principal source of error as input offset voltage, gain error, common mode rejection ration, are described

separately in the electrical characteristics. This section summarizes the most important error to take into account

during a design phase.

•

Input offset voltage error

In a precision domain most of the time the input offset can be a major influence in the output error. It is so

important to take it into account and also the derivation in temperature as depicted by equation 3:

TSC210, TSC211, TSC212, TSC213, TSC214, TSC215

Input offset voltage drift overtemperature

DS13237 - Rev 6

page 16/38