TSU112IY datasheet(21/32 Pages) STMICROELECTRONICS

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Where Vio drift is the measured drift value in the specified test conditions after 1000 h stress duration.

5.5

Using the TSU112IY with sensors

The TSU112IY has MOS inputs, thus input bias currents can be guaranteed down to 10 pA maximum at ambient

temperature. This is an important parameter when the operational amplifier is used in combination with high

impedance sensors.

The TSU112IY is perfectly suited for trans-impedance configuration. This configuration allows a current to be

converted into a voltage value with a gain set by the user. It is an ideal choice for portable electrochemical gas

sensing or photo/UV sensing applications. The TSU112IY, using trans-impedance configuration, is able to provide

a voltage value based on the physical parameter sensed by the sensor.

5.6

Fast desaturation

When the TSU112IY goes into saturation mode, it takes a short period of time to recover, typically 420/880 µs.

When recovering after saturation, the TSU112IY does not exhibit any voltage peaks that could generate issues

(such as false alarms) in the application (see Figure 14).

We can observe that this circuit still exhibits good gain even close to the rails i.e. Avd greater than 88 dB for Vcc =

3.3 V with Vout varying from 200 mV up to a supply voltage minus 200 mV. With a trans-impedance schematic, a

voltage reference can be used to keep the signal away from the supply rails.

5.7

Using the TSU112IY in comparator mode

The TSU112IY can be used as a comparator. In this case, the output stage of the device always operates in

saturation mode. In addition, Figure 3 shows that the current consumption is not higher and even decreases

smoothly close to the rails. The TSU112IY is obviously an operational amplifier and is therefore optimized for use

in linear mode. We recommend using the TS88 series of nanopower comparators if the primary function is to

perform a signal comparison only.

5.8

ESD structure of the TSU112IY

The TSU112IY is protected against electrostatic discharge (ESD) with dedicated diodes (see Figure 1). These

diodes must be considered at application level especially when signals applied on the input pins go beyond the

power supply rails (VCC+) or (VCC-).

Figure 42. ESD structure

TSU112IY

Current through the diodes must be limited to a maximum of 10 mA as stated in Table 1. A serial resistor on the

inputs can be used to limit this current.

TSU112IY

Using the TSU112IY with sensors

DS13616 - Rev 1

page 21/32

TSU112IY Datenblatt(PDF) 21 Page - STMicroelectronics