High Current PN Half Bridge
BTS 7960
Block Description and Characteristics
4.4
Control and Diagnostics
Input Circuit
4.4.1
The control inputs IN and INH consist of TTL/CMOS compatible schmitt triggers with
hysteresis which control the integrated gate drivers for the MOSFETs. Setting the INH
pin to high enables the device. In this condition one of the two power switches is switched
on depending on the status of the IN pin. To deactivate both switches, the INH pin has
to be set to low. No external driver is needed. The BTS 7960 can be interfaced directly
to a microcontroller.
4.4.2
Dead Time Generation
In bridge applications it has to be assured that the highside and lowside MOSFET are
not conducting at the same time, connecting directly the battery voltage to GND. This is
assured by a circuit in the driver IC, generating a so called dead time between switching
off one MOSFET and switching on the other. The dead time generated in the driver IC is
automatically adjusted to the selected slew rate.
4.4.3
Adjustable Slew Rate
In order to optimize electromagnetic emission, the switching speed of the MOSFETs is
adjustable by an external resistor. The slew rate pin SR allows the user to optimize the
balance between emission and power dissipation within his own application by
connecting an external resistor RSR to GND.
4.4.4
Status Flag Diagnosis With Current Sense Capability
The status pin IS is used as a combined current sense and error flag output. In normal
operation (current sense mode), a current source is connected to the status pin, which
delivers a current proportional to the forward load current flowing through the active high
side switch. If the high side switch is inactive or the current is flowing in the reverse
direction no current will be driven except for a marginal leakage current IIS(LK). The
external resistor RIS determines the voltage per output current. E.g. with the nominal
value of 8500 for the current sense ratio kILIS = IL / IIS, a resistor value of RIS = 1kΩ leads
to VIS = (IL / 8.5 A)V. In case of a fault condition the status output is connected to a
current source which is independent of the load current and provides IIS(lim). The
maximum voltage at the IS pin is determined by the choice of the external resistor and
the supply voltage. In case of current limitation the IIS(lim) is activated for 2 * tCLS
.
Data Sheet
17
Rev. 1.1, 2004-12-07
INFINEON [ Infineon ]
