TLE7189QK_16 Datasheet, PDF (17/29 Pages) Infineon Technologies AG – 3-Phase Bridge Driver IC

TLE7189QK
5.2
Protection and Diagnostic Functions
5.2.1 Short Circuit Protection
The TLE7189QK provides a short circuit protection for the external MOSFETs. It is a monitoring of the drain-
source voltage of the external MOSFETs. As soon as this voltage is higher than the short circuit detection limit, a
capacitor will be charged. The high side and the low side output stage of the same half bridge use the same
capacitor (see Figure 3 ). This capacitor is discharged permanently with a current which is about 2 times smaller
than the charging current. This charging and discharging ratio is specified with the help of duty cycle where a short
is detected or not detected.
After a delay of about 12µs all external MOSFETs will be switched off until the driver is reset by the ENA pin. The
error flag is set.
The drain-source voltage monitoring of the short circuit detection for a certain external MOSFET is active as soon
as the corresponding input is set to "on" and the dead time is expired.
The short circuit detection level is adjustable in an analogue manner by the voltage setting at the SCDL pin. There
is a 1:1 translation between the voltage applied to the SCDL pin and the drain-source voltage limit. E.g. to trigger
the SCD circuit at 1V drain-source voltage, the SCDL pin must be set to 1V as well. The drain-source voltage limit
can be chosen between 0.7 ... 2.5V.
If the SCDL pin is left open, the short circuit detection level will be set internally to a specified value. In case SCDL
is connected to GND the detection level is low. If SCDL is connected to 3.3V, the detection level is about 3.2V.
In the TLE7189QK the short circuit detection functionality can be tested by setting the SCDL pin to voltages lower
than 0.4V, switching off the low side MOSFETs and switching on one or more high side MOSFETs. In this test, a
short circuit will be detected even without current in the external MOSFET (VDH-SHx > V_TSCD1).
This test function can be used as well to detect an open VDH pin. If VDH is open during this test, no SCD error
will be reported.
A setting of 5V at the SCDL pin will disable the short circuit protection function.
5.2.2 Dead Time and Shoot Through Protection
In bridge applications it has to be assured that the external high side and low side MOSFETs are not "on" at the
same time, connecting directly the battery voltage to GND. The dead time generated in the TLE7189QK is fixed
to a minimum value. This function assures a minimum dead time if the input signals coming from the µC are faulty.
The exact dead time of the bridge is usually controlled by the PWM generation unit of the µC.
In addition to this dead time, the TLE7189QK provides a locking mechanism, avoiding that both external
MOSFETs of one half bridge can be 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. The conflicting input signals will not generate an error message.
5.2.3 Under Voltage Shut Down
The TLE7189QK has an integrated under voltage shut down, to assure that the behavior of the device is
predictable in all voltage ranges.
If the voltage of a charge pump buffer capacitors CBx reaches the under voltage shut down level for a minimum
specified filter time, the gate-source voltage of all external MOSFETs will be actively pulled to low. In this situation
the short circuit detection of this output stage is deactivated to avoid a latching shut down of the driver.
As soon as the charge pump buffer voltage recovers, the output stage condition will be aligned to the input patterns
automatically.This allows to continue operation of the motor in case of under voltage shut down without a reset by
the µC.
Data Sheet
17
Rev. 2.2, 2016-01-28