Datasheet TLE6280GP

6

2007-07-19

Dead Time and Shoot through option.

In bridge applications it has to be assured that the external high-side and low-side Mosfets

are not “on” at the same time, such that the battery voltage is directly connected to GND.

This is usually assured by the integration of delays in a driver IC, generating a so-called

dead time between switching off the external Mosfet and switching on the other Mosfet of the

same half-bridge.

The dead times generated in the TLE6280GP are adjustable. The dead time generated by

the TLE6280GP can be varied from 100ns to 4µs by connecting an external resistor from the

DT pin to GND. The dead time has to be long enough to avoid a short between battery and

GND, while the dead time should be as short as possible to reduce extra power dissipation

in the external Mosfets.

In addition to this adjustable delay, the TLE6280GP provides a locking mechanism, prevent-

ing both external Mosfets of one half-bridge from being switched on at the same time. This

functionality is called shoot through protection.

If the command to switch on both high and low-side switches in the same half-bridge is given

at the input pins, the command will be ignored. (See dead time diagrams, fig. 6-8)

This shoot through protection can be deactivated by setting the MFP-pin to 5V.

Short circuit protection / current limitation

The TLE6280GP provides a short circuit protection for the external Mosfets, by monitoring

the Drain-Source voltage of the external Mosfets. As soon as this voltage is higher than the

short circuit detection limit, the Gate-Source voltage of this Mosfet will be limited to twice the

voltage at the MFP-Pin, providing a current limitation.

The short circuit detection level is dependent upon the voltage of the MFP pin as well (see

diagrams).

After a delay of about 11µs all external Mosfets will be switched off until the driver is reset by

the MFP pin. The error flag is set.

The Drain-Source voltage monitoring of the short circuit detection for certain external Mos-

fets is active as soon as the corresponding input is set to “on” and the dead time is expired.

This feature provides a 2-step switch-on behavior for each regular switching-on of a Mosfet.

Description of MFP pin (Multi functional pin)

The MFP pin has multiple tasks:

1) Reset the device.

2) Adjust the short circuit detection level of the external Mosfet and define the gate voltage

limitation for current limitation in case of short circuit

3) Deactivate the shoot-through protection

Fig 4. shows the internal structure of the MFP pin.

Condition of MFP pin

Function

0 – 1.1V

Disable the driver. All external Mosfets will be actively

switched off

2.5 – 4.0 V

Adjustable short circuit detection level combined with adjust-

able gate voltage limitation for current limitation. Shoot-

through protection is active.

> 4.5V

Shoot-through protection deactivated.