High Current PN Half Bridge
BTS 7960
Block Description and Characteristics
4.3
Protection Functions
The device provides integrated protection functions. These are designed to prevent IC
destruction under fault conditions described in the data sheet. Fault conditions are
considered as “outside” normal operating range. Protection functions are not to be used
for continuous or repetitive operation, with the exception of the current limitation
(Chapter 4.3.4). In a fault condition the BTS 7960 will apply the highest slew rate
possible independent of the connected slew rate resistor. Overvoltage, overtemperature
and overcurrent are indicated by a fault current IIS(LIM) at the IS pin as described in the
paragraph “Status Flag Diagnosis With Current Sense Capability” on Page 17 and
Figure 10.
In the following the protection functions are listed in order of their priority. Overvoltage
lock out overrides all other error modes.
4.3.1
Overvoltage Lock Out
To assure a high immunity against overvoltages (e.g. load dump conditions) the device
shuts the lowside MOSFET off and turns the highside MOSFET on, if the supply voltage
is exceeding the over voltage protection level VOV(OFF). The IC operates in normal mode
again with a hysteresis VOV(HY) if the supply voltage decreases below the switch-on
voltage VOV(ON). In H-bridge configuration, this behavior of the BTS 7960 will lead to
freewheeling in highside during over voltage.
4.3.2
Undervoltage Shut Down
To avoid uncontrolled motion of the driven motor at low voltages the device shuts off
(output is tri-state), if the supply voltage drops below the switch-off voltage VUV(OFF). The
IC becomes active again with a hysteresis VUV(HY) if the supply voltage rises above the
switch-on voltage VUV(ON)
.
4.3.3
Overtemperature Protection
The BTS 7960 is protected against overtemperature by an integrated temperature
sensor. Overtemperature leads to a shut down of both output stages. This state is
latched until the device is reset by a low signal with a minimum length of treset at the INH
pin, provided that its temperature has decreased at least the thermal hysteresis ∆T in the
meantime.
Repetitive use of the overtemperature protection might reduce lifetime.
4.3.4
Current Limitation
The current in the bridge is measured in both switches. As soon as the current in forward
direction in one switch (high side or low side) is reaching the limit ICLx, this switch is
deactivated and the other switch is activated for tCLS . During that time all changes at the
Data Sheet
13
Rev. 1.1, 2004-12-07
INFINEON [ Infineon ]
