6

Typical applications

Low-power signal conditioning

The TS3121 is a key circuit element for signal conditioning with fast response time in a low-power environment. It

was designed for regular turning on and off of the supply line. For this reason the TS3121 comes with fail-safe

input and output pins that allow the presence of voltage when the comparator is not supplied (VCC = 0 V).

Figure 54 shows a typical sensor conditioning application. The sensor signal can come from various sources, for

example: light, position, current, or temperature monitoring. The supply for the reference voltage TS431 and for

the comparator are provided by the GPIO pin of a microcontroller which is activated during 100 µs every 100 ms.

This duty cycle effectively divides the overall power consumption by a factor of thousand from typically 60 µA to

only 60 nA and hence considerably below the consumption of a low-power comparator. The pull-up resistor is

connected to the supply of the microcontroller. In the displayed application the feedback signal is HIGH for VCC =

0 V or for a sensor signal inferior to the reference voltage. The feedback signal is LOW when the sensor signal is

higher than the reference voltage and after a maximum delay of tturn-on = 15 µs from the moment where VCC

passes VCC-min. An embedded hysteresis of 1 mV prevents the comparator from instable toggling during the

transition phase when the sensor voltage and reference voltage are equivalent (Vdiff = Vio).

Figure 54. Typical application schematic

TS431

Vref = 1.24V

STM32

GPIO provides Vcc

Sensor

(light, position,

current, ...)

TS3121

threshold

Rpu

3.3V

feedback

18 kΩ

TS3121, TS3121A

Typical applications

DS14484 - Rev 2

page 24/34