L9300 datasheet(30/178 Pages) STMICROELECTRONICS

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TRK outputs are short to battery protected to avoid reverse current into VDD1 pin: in case the protection is

triggered a diagnostic bit is set in the dedicated SPI register.

An out of regulation comparator is implemented: this comparator senses when the internal current limitation

circuitry is activated to regulate properly the output voltage due to either a low drop condition or an overcurrent

condition. Once out of regulation condition is detected a flag is set in SPI registers and latched until read. The

diagnostic is not masked during power-up phase.

TRK regulators have a thermal protection with thermal sensors shared with VDD2 regulator. In case the

temperature threshold is reached and the out of regulation flag is set, only the regulator in fault condition is turned

off and a dedicated diagnostic bit is set. Once the sensed temperature is decreased below the shutdown

threshold plus a thermal hysteresis, the regulator is automatically turned on with soft start function. T_SD_TRK is

the bit that latches the thermal shutdown and it is cleared on SPI read.

A dedicated disable SPI bit TRKn_DIS (default condition: track enabled) is present and it can be used to avoid

thermal on/off oscillations in case the short on output pin cannot be removed.

Figure 14. TRK regulators

TRK1

VBATP

Control

loop

Driver

TRK1

TRK_SEL

VDD1

GADG1107170903PS

8.5.2

WSI configuration

Functional description

If TRK_SEL pin is grounded, the device provides 4-wheel speed sensor interfaces on TRKn pins: the status of

each sensor is reported to the microcontroller via the SPI. The input signal of an active sensor is a rectangular

signal with variable pulse width and output currents of 2 levels (7/14 mA) or 3 levels (7/14/28 mA) depending on

the sensor itself. The sensor types are standard active 2-level wheel speed sensors (7/14 mA).

A simplified block diagram of the interface is shown below. The interface supply is given on the VDD1 pin. 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. Decoded data are

then output through the Remote Sensor Data Registers (WSIRSDRx). Received signals can be processed to the

corresponding discrete logic output pin DOUT1-DOUT4. 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 (WSIRSDRx).

L9300

Power supply

DS12258 - Rev 5

page 30/178

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