6.14

Application example

Power supply monitoring and OCP function.

The TSC21x is used to sense the current into the load, and thus in both directions, in a very accurate way.

Figure 49. Power supply monitoring and OCP function

TSC21x

Vcc

-

+

Vref

10nF

100nF

power supply

Rshunt

R

load

Ref

Comparator

D-latch

HCF4013YM013TR

Vcc

+

-

Over current protection

Vcc

Microcontroller

Vcc

STM32

TS3021

Current sensing

When a short-circuit or overcurrent occurs, the application must be switched off as quickly as possible. And

moreover, after such event, the application must not restart by itself and must stay switched off until a manual

reload is applied. The TS3021 is a high speed comparator, which combined with D flip-flop HCF4013, is used to

realize a latch function in case of an overcurrent event.

In case of overcurrent, the output of the current sensing rises above the Ref voltage and so the output of the

comparator changes from a low state to a high state.

This information is directly latched because of the D flip-flop HCF4013. And after such an event, the output of the

HCF4013 (Q1) changes from high state to a low state.

The (Q1) is also supervised by a GPIO of the MCU, which can be informed in case of an overcurrent event.

To restart the application and un-latch the D flip-flop, a clock signal must be applied on pin CLOCK1 of the

HCF4013.

A first approach calculation by considering a Vcc voltage at 3.3 V.

The current sensing TSC213 has a slew rate of 0.85 V/µs. After an overcurrent event, its output is saturated and

may rise up to its maximum output voltage, here 3.3 V. If we consider the worst case the output of the TSC213 is

close to 0 V, the current sensing would need 3.9 µs to pass from 0 V to 3.3 V, after the overcurrent event.

The comparator TS3021 is a high speed comparator with a propagation delay TPLH of 75 ns max. to change its

state from low to high.

The D flip-flop has a propagation delay TPHL of 400 ns to change its state from high to low.

So after an overcurrent, the system takes, in worst condition, less than 4.4 µs to switch off the power (extra

margin should be taken considering that the propagation delay of the comparator depends on the overdrive).

TSC210, TSC211, TSC212, TSC213, TSC214, TSC215

Application information

DS13237 - Rev 7

page 26/38