In this configuration the Vref pin is connected to the Vcc power supply. The output common mode voltage is then

automatically set to Vcc voltage when no current flows through the Rshunt resistance. This configuration allows the

full-scale output in unidirectional mode. It allows to measure a current as described in Figure 32

•

Bidirectional operation

Bidirectional mode of operation allows the device to measure currents through a shunt resistor in two directions.

The output reference can be set anywhere within the power supply range. If the output common mode voltage

is set at mid-range, the full-scale current measurement range is equal in both directions. It can be done by

connecting Vref pins to a reference voltage as suggested by Figure 33. In case the current measurement is not

equal in both directions, users can set the output in a non-symmetrical configuration, adjusting Vref according to

user needs.

Figure 33. External supply

OUT

VREF

V

Shunt

resistor

In-

In+

R1

R2

R3

Gnd

R4

-

+

CC

Reference

Voltage

Another simpler way to generate the reference voltage to fix the output common mode voltage can be used.

As, for example, a resistive divider; in this case, as the VREF pin must be connected to a low impedance, it is

important to add a buffer stage between the VREF pin and the resistive divider. The buffer can be simply done with

an opamp as TSB611 in follower configuration.

If for any reason the voltage on the Vref pin exceeds the power supply by 0.5 V, the ESD diodes become

conductive and excessive current can flow through them. Without limitation this overcurrent can damage the

device. In this case, it is important to limit the current to 5 mA.

6.4

RSENSE selection

The selection of the shunt resistor is a trade-off between dynamic range and power dissipation.

Generally, in high current sensing application, the main focus is to reduce as much as possible the power

dissipation (I²R) by choosing the smallest value of shunt. It could be quite easy if full-scale current to measure is

small.

In low current application, the Rsense value could be higher, to minimize the impact of the offset voltage of the

circuit. Still keep in mind that due to input bias of several µA the TSC21x cannot measure current in the same

range, when the common mode voltage overpasses 2.5 V (refer to Section 6.2 Theory of operation).

The trade-off is mainly when a dynamic range of current to measure is large, meaning ability to measure with the

same shunt value low current to high current. Generally, the current full scale (Imax-Imin) defines the shunt value

thanks to the full output voltage range, the gain of the TSC21x.

Let’s illustrate with a simple example. In battery application a current in the range of 1 A to 10 A must be

measured. A TSC213 with a gain of 50 is chosen.

TSC210, TSC211, TSC212, TSC213, TSC214, TSC215

RSENSE selection

DS13237 - Rev 6

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