AN2836 datasheet(19/57 Pages) STMICROELECTRONICS

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AN2836

Designing an application with L6225, L6226, L6227

Doc ID 15084 Rev 1

19/57

Figure 12.

Logic input pins

4.10

EN pins

The ENA, ENB pins are, actually, bi-directional. As an input, with a comparator similar to the

other logic input pins (TTL/CMOS with hysteresis), they control the state of the power

DMOS. When each of the two pins is at a low logic level, all the power DMOS of the

corresponding H-bridge (A or B) are turned off. In L6225 and L6227 the EN pins are also

connected to the two corresponding open-drain outputs of the protection circuits that pull the

pins to GND if overcurrent in the corresponding H-bridge or overtemperature conditions

exist. In L6226 the open-drain outputs are on separate pins, OCDA and OCDB, allowing

easier external diagnostics and overcurrent management. For this reason, with L6225 and

L6227 (and L6226 if EN pins are connected to DIAG pins), EN pins must be driven through

a series resistor of 2.2 k

Ω minimum (for 5 V logic), to allow the voltage at the pin to be pulled

below the turn-off threshold.

A capacitor (CEN in Figure 13) connected between each EN pin and GND is also

recommended, to reduce the RMS value of the output current when overcurrent conditions

persist (see Section 4.13). The EN pin must not be left unconnected.

Figure 13.

ENA and ENB input pins

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