Datasheet

DocID15567 Rev 6 29/53
L99H01 Device description
52
3.11 Current sense amplifier (CSA)
The current sense amplifier (CSA) is specially designed for current shunt automotive
applications. It is a bidirectional, single-supply difference amplifier for amplifying small
differential voltages in a wide common mode voltage range (-4 V to (V
CP
- 8) V). It supports
the current measurement at two shunts. The result of respective shunt can be multiplexed to
the microcontroller compatible output voltage by a SPI command.
A gain of 50, 20 or 10 is SPI programmable. The inputs (CSI1+ / CSI1- and CSI2+ / CSI2-)
are build as a transconductance stage. Therefore a series resistor (for filtering etc.) should
not exceed 50 Ω to keep the additional gain error below 1%.
The output works at half scale: V
CSO0
= (0,5 * V
CC
) V for V
IDIFF
= 0 V. An internal offset
measurement is in normal mode available with the "OFF_CAL" SPI-bit. If this bit is set to
logic "1" the input pins are disconnected from the amplifier and a virtual zero input
differential voltage is selected.
3.12 Thermal sensor interface / H-bridge switch-off input
The TS/ACT_OFF pin is configurable by SPI with the EXT_TS bit. This pin could be used as
temperature sensor interface for the H-bridge or external off for all gate drivers. The output
bias current ITS_bias is on for EN = high.
3.12.1 EXT_TS-bit = low (active off)
The TS/ACT_OFF input is used as a logic driver control input, without filter delay and
without latching the information.
Pulling the TS/ACT_OFF pin below the programmed threshold all gate drivers are
switched-off and the OT_EXT bit is set.
Increasing the voltage at TS/ACT_OFF pin above the programmed threshold the device
remains to the status set by DIR and PWM-pins and the OT_EXT bit is reseted.
The threshold is programmable by SPI with the registers EXTTH_5:0.
3.12.2 EXT_TS-bit = high (thermal sensor interface)
With the thermal sensor interface external diodes can be used to control the temperature of
the external H-bridge. When the diode forward voltage decreases below the reference
voltage for longer than the internal filter time (64 µs) the OT_EXT bit is set and the driver
switches in resistive low (see Section 3.4: Resistive low).
In this mode the OT_EXT-status-bit has to be cleared to reactivate the gate drivers.
The threshold is programmable by SPI with the registers EXTTH_5:0.
3.13 Watchdog
The tasks of the watchdog is to monitor the microcontroller during normal operation within a
nominal trigger cycle of 60 ms. The microcontroller has to restart the watchdog timer by
sending the watchdog restart bit via SPI repeatedly within the watchdog time T
WDTO
. If no
correct watchdog service is sent from the microcontroller, all gate drivers switch in sink