L99H02 datasheet(29/51 Pages) STMICROELECTRONICS

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DS12547 Rev 6

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L99H02

Device description

3.11

Current sense amplifier (CSA)

The current sense amplifier (CSA) is specially designed for current sensing in automotive

applications. It is a bidirectional, single-supply amplifier for amplifying small differential

voltages in a wide common mode voltage range (-4 V to (VCP - 8) V). It supports the current

measurement at two shunts. The result of the 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 built as a transconductance stage. Therefore a series resistor (for filtering etc.) should

not exceed 50

 to keep the additional gain error below 1%.

The output works at half scale: VCSO0 = (0,5 * VCC) V for VIDIFF = 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 input pin is configurable by SPI with the EXT_TS bit. This pin could be

used as temperature sensor interface for the power stage temperature sensors or as

external switch off input for the power stage (all the external MOSFETs). The output bias

current for the power stage temperature sensors 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 shuts off all the MOSFETs

and sets the OT_EXT bit.

Increasing the voltage at TS/ACT_OFF pin above the programmed threshold brings back

the MOSFETs to the status set by DIR and PWM-pins and resets the OT_EXT bit.

The threshold is programmable by SPI with the bits EXTTH_5:0.

3.12.2

EXT_TS-bit = high (thermal sensor interface)

The thermal sensor interface together with the thermal sensor diodes, can be used to

control the temperature of the external H-bridge. When the drop over the diodes chain

decreases below the reference voltage for longer than the internal filter time (64 µs) the

OT_EXT bit is set and the drivers switch in sink condition.

In this mode the OT_EXT-status-bit has to be cleared through a software reset to reactivate

the gate drivers.

The threshold is programmable by SPI with the bits EXTTH_5:0.

3.13

Watchdog

The task 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

setting the watchdog restart bit via SPI repeatedly within the watchdog time TWDTO. If no

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