E-L9823 Datasheet, PDF (13/19 Pages) STMicroelectronics – Octal low-side driver for bulb, resistive and inductive loads with serial input control, output protection and diagnostic

L9823
3
Functional description
Functional description
3.1
General
The L9823 integrated circuit features 8 power low-side-driver outputs. Data is transmitted to
the device using the Serial Peripheral Interface = SPI protocol. The power outputs features
voltage clamping function for flyback current recirculation and are protected against short
circuit to Vbat.
The diagnostics recognizes two outputs fault conditions: 1) overcurrent and thermal
overload in switch-ON condition and 2) open load or short to GND in switch-OFF condition
for all outputs. The outputs status can be read out via the serial interface.
The chip internal Reset is a OR function of the external Reset signal and internally
generated undervoltage Reset signal.
3.2
Output stages control
Each output is controlled with its latch and with a common Reset line, which enables all
outputs.
The control data are transmitted via the SI input, the timing of the serial interface is shown in
Figure 4.
The device is selected with low CSB signal and the input data are transferred into the 8 bit
shift register at every falling SCLK edge. The rising edge of the CSB latches the new data
from the shift register to the drivers.
Figure 4. Timing of the serial interface
#3"
TSCLCH THCLCL
TCLH
TCLL
3#,+
TCSDV
TPCLD
3/
NOTDEFINED
$
TSCLD
THCLD
3)
$
$
TSCLCL
THCLCH
TPCHDZ
$
$
'!0'03
The SPI register data are transferred to the output latch at rising CSB edge. The digital filter
between CSB and the output latch ensures that the data are transferred only after 8 SCLK
cycles or multiple of 8 SCLK cycles since the last CSB falling edge. The CSB changes only
at low SCLK.
Doc ID 7791 Rev 5
13/19