TIC10024-Q1 Datasheet, PDF (14/81 Pages) Texas Instruments – 24-Input Multiple Switch Detection Interface (MSDI) Device With Adjustable Wetting Current for Automotive Systems

TIC10024-Q1
SCPS268 – SEPTEMBER 2017
www.ti.com
8.3 Feature Description
8.3.1 V_S Pin
The V_S supply provides power to the entire chip and it is designed to be connected directly to a 12-V automotive
battery via a reverse-polarity blocking diode.
8.3.2 V_DD Pin
The V_DD supply is used to determine the logic level on the SPI communication interface, source the current for
the SO driver, and sets the pull-up voltage for the CS pin. It can also be used as a possible external pull-up
supply for the INT pin in addition to the V_S and it shall be connected to a 3 V to 5.5-V logic supply. Removing
V_DD from the device disables SPI communications but does not reset the register configurations.
8.3.3 Device Initialization
When the device is powered up for the first time, the condition is called Power-On Reset (POR), which sets the
registers to their default values and initializes the device state machine. The internal POR controller holds the
device in a reset condition until V_S has reached V_{POR_R}, at which the reset condition is released with the device
registers and state machine initialized to their default values. After the initialization process is completed, the INT
pin is asserted low to notify the microcontroller, and the register bit POR in the INT_STAT register is asserted to
logic 1. The SPI flag bit POR is also asserted at the SPI output (SO).
During device initialization, factory settings are programmed into the device to allow accurate device operation.
The device performs a self-check after the device is programmed to ensure correct settings are loaded. If the
self-check returns an error, the CHK_FAIL bit in the INT_STAT register will be flagged to logic 1 along with the
POR bit. If this event occurs the microcontroller is recommended to initiate software reset (see section Software
Reset) to re-initialize the device to allow the correct settings to be re-programmed.
8.3.4 Device Trigger
After device initialization, the TIC10024-Q1 is ready to be configured. The microcontroller can use SPI
commands to program desired settings to the configuration registers. Once the device configuration is
completed, the microcontroller is required to set the bit TRIGGER in the CONFIG register to logic 1 in order to
activate wetting current and start external switch monitoring.
After switch monitoring initiates, the configuration registers turn into read-only registers (with the exception of the
TRIGGER, CRC_T, and RESET bits in the CONFIG register and all bits in the CCP_CFG1 register). If at any
time the device setting needs to be re-configured, the microcontroller is required to first set the bit TRIGGER in
the CONFIG register to logic 0 to stop wetting current and switch monitoring. The microcontroller can then
program configuration registers to the desired settings. Once the re-configuration is completed the
microcontroller can set the TRIGGER bit back to logic 1 to re-start switch monitoring.
Note the cyclic redundancy check (CRC) feature stays accessible when TRIGGER bit is in logic 1, allowing the
microcontroller to verify device settings at all time. Refer to section Cyclic Redundancy Check (CRC) for more
details of the CRC feature.
8.3.5 Device Reset
There are 3 ways to reset the TIC10024-Q1 and re-initialize all registers to their default values:
8.3.5.1 V_S Supply POR
The device is turned off and all register contents are lost if the V_S voltage drops below V_{POR_F}. To turn the device
back on, the V_S voltage must be raised back above V_{POR_R}, as illustrated in Figure 7. The device then starts the
initialization process as described in section Device Initialization.
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