UM1477

General description

Doc ID 022373 Rev 1

13/22

The L6230 integrates a non-dissipative overcurrent detection circuit (OCD) for full

protection.

To implement the overcurrent detection, a sensing element that delivers a small but precise

fraction of the output current is implemented with each high side power MOSFET. This

current is compared with an internal reference current IREF.

comparator signals a fault condition. When a fault condition is detected, an internal open

drain MOSFET connected to pin DIAG-EN is turned on. Pin DIAG-EN is to be used to signal

the fault condition to a MCU.

The internal comparator is used for the current control, for more details refer to Section 4.3

which follows.

4.3

Current sensing circuitry

In the 6-step driving method only one sense resistor is needed, the three SENSE pins are

Figure 8.

Current sensing circuitry

The voltage across the shunt resistor is conditioned by operational amplifiers (TSV991)

which provide the proper feedback signals to the non-inverting input of the L6230 internal

comparator (CP+ pin). The op amp output voltage range is optimized for a given phase

current range and the comparator input dynamics. The op amp output voltage is

proportional to the sense voltage; when the CP+ voltage becomes greater than the

reference voltage applied at inverting input CP-, the comparator open drain output is

switched on pulling down the CPOUT pin.

This signal may be managed by the MCU to generate the proper input sequence for a 6-step

driving method with current control and to select what current decay method to implement.

When the CP+ voltage decreases below the CP- voltage, the open drain is switched off and

the voltage at the CPOUT pin starts to increase charging the capacitor connected to the pin

(C8 in Figure 2 board schematic).

The reference voltage at pin CP- is set according to the sense resistor value and the desired

regulated current.