L9680 datasheet(175/277 Pages) STMICROELECTRONICS

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L9680

Remote sensor interface

276

Remote sensor interface

The L9680 contains 4 remote sensor interfaces, capable of supporting PSI-5 protocol

(synchronous mode, increased voltage, extended range) and active wheel speed sensors.

A simplified block diagram of the interface is shown below. The interface supply is given on

the SATBUCK pin (refer to Figure 3: Power supply block diagram). The circuitry consists of

a power interface that mirrors current flowing in the external sensor and transmits this

current information to the decoder, which produces a digital value for each remote sensor

channel. The voltage at the RSUx pins can be limited by the power interface in case of

SATBUCK supply overvoltage to protect the external sensors. Decoded data are then

output through the Remote Sensor Data Registers (RSDRx). Received signals can be

processed to the corresponding discrete logic output pin WS0-WS3. The power interface

also contains error detection circuitry. When a fault is detected, the error code is stored in a

global SPI data buffer in the Remote Sensor Data Registers (RSDRx).

Figure 38. Remote sensor interface logic blocks

Remote sensor configuration can be addressed via the Remote Sensor Configuration

Registers (RSCRx). Some of the bit fields in the RSCRx registers are available depending

on the chosen configuration, remote sensor rather than wheel speed sensors. In particular,

TSxDIS bit allows overriding the time slot control for PSI5 I/F and BLKTxSEL allows

selection between 5ms and 10ms for the blanking time applied to the current limitation fault

detection each time a channel is activated.

The Remote Sensor Control Register (RSCTRL) allow for interface channels to be switched

on and Off and for Sync Pulse control via SPI.

The remote sensor interface reports both data information and fault information in the

Remote Sensor Data Register (RSDRx). The device accommodates for a total of 12 data

registers. Independent data registers are defined for each remote sensor interface and are

formatted differently based on whether the interfaces are programmed for PSI-5 remote

sensor functions or active wheel speeds.

In the VDA sensor communication, data bit D0 in the RSDRx register might be used by the

sensor as a fault bit. Therefore, this bit is latched as D0_L in order to detect whether a fault

has occurred: the eight data bits are updated every speed pulse so intermittent fault

conditions could be lost. This bit is cleared-upon-read.

If the device detects an error on the sensor interface, the MSB in RSDRx (FLTBIT) will be

set to '1' and the following bits will be used to report the detected errors. Otherwise, the

are explained in the following sections.

L9680 Datasheet(PDF) 175 Page - STMicroelectronics