L9305EP datasheet(29/107 Pages) STMICROELECTRONICS

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6.4

Solenoid driver and load diagnostic

6.4.1

Thermal protection

Each solenoid channel has a dedicated temperature sensor that continuously monitors the temperature of the

Low Side and of the High Side power transistor. Temperature information is available in the dedicated SPI register

Channel_x.TEMPMON. Register data can be decoded from the SPI frame using the following formula:

TJ=1.353*TemperatureMonitor−74 Co

(2)

Should channel temperature reach the thermal warning threshold T_WARN, the thermal warning flag is set in the

EXCEPTIONS1 register bit D[15]. The warning flag is latched and is cleared upon SPI read if the thermal warning

condition is no longer present.

Should channel temperature continue to rise up to the thermal shutdown threshold T_SD, the related channel is

placed in tristate mode (setting the Solenoid Driver Status bits to 01, but keeping the programmed current set-

point). This event has a dedicated fault flag in the EXCEPTIONS1 register, bit D[0]. Channel activation is

prevented if thermal shut down condition is still present on SPI read. This fault is latched and is cleared upon SPI

read if the fault is no longer present. Channel thermal shutdown temperature has no hysteresis, but user can

decide which temperature is low enough to re-enable the channel. In fact, by monitoring Channelx.TEMPMON

further degree of flexibility is provided.

6.4.2

Overcurrent protection

Overcurrent protection is present for each HS and LS solenoid driver. The overcurrent threshold is selectable

through SPI register Channel_x.CONFIGURATION1 bit D[6].

Should an overcurrent fault be detected (on HS or on LS), the related channel is put in tri-state (setting the

Solenoid Driver Status bits to 01, but keeping programmed current set-point) and a dedicated diagnostic bit is set

in register Channel_x.EXCEPTION1, bits D[2] for HS and D[1] for LS. To restart the channel, the MCU must clear

the fault bit by reading the fault register and re-enable the channel.

6.4.3

Supply disconnection

When a solenoid channel is configured for low side operation, current recirculation occurs through the internal

high side transistor. If the supply Vs_solX of the high side driver is lost, the voltage at LOAD_SOLx pin can

become unpredictable and possibly exceed the absolute rating of the device. To prevent this condition from

damaging the device, the low side driver has an integrated clamping circuit to limit the peak voltage.

Should the low side clamping structure be activated during normal operation (i.e. solenoid supply line within

normal operating range), the channel is put in tri-state (setting the Solenoid Driver Status bits to 01) and the Low

Side Clamp Active fault flag D[3] is set in the EXCEPTIONS1 register. To restart the channel, the MCU must clear

the fault by reading the EXCEPTIONS1 register and re-enable the channel.

Activation of LS clamp during a load dump event could damage the device due to the high energy of load dump

event. To avoid this condition, the LS clamp circuitry is automatically disabled when VBATP pin exceeds deep

over-voltage threshold, as defined in Section 8.1.6.

6.4.4

Off state solenoid diagnostics

The device provides independent off-state diagnostics for each channel. Simplified diagrams are shown in

Figure 15 and Figure 16 below, depending on the chosen configuration.

L9305

Current control drivers

DS12774 - Rev 10

page 29/107

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