TIC10024-Q1 Datasheet, PDF (29/81 Pages) Texas Instruments – 24-Input Multiple Switch Detection Interface (MSDI) Device With Adjustable Wetting Current for Automotive Systems

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TIC10024-Q1
SCPS268 – SEPTEMBER 2017
Device Functional Modes (continued)
If the switch position changes between two active polling times, no interrupt will be generated and the status
register (IN_STAT_COMP) will not reflect such a change. An example is shown in Figure 19.
Wetting
current
Switch
state
Initial switch
state change
/INT
/INT asserted
due to initial
state change
/CS
Ignored
switch state
change
Time
Figure 19. Example For Ignored Switch Position Change Between 2 Wetting Current Cycles
8.4.3 Additional Features
There are additional features that can be enabled during continuous and polling mode to increase robustness of
device operation or provide more system information. These features are described in detail in the following
sections.
8.4.3.1 Clean Current Polling (CCP)
In real automotive system, lower wetting current is generally desired to reduce the system's overall power
consumption. However, certain system design requires 10 mA or higher cleaning current to clear oxide build-up
on the mechanical switch contact surface when the current is applied to closed switches. A special type of
polling, called the Clean Current Polling (CCP), can be used for this application.
If CCP is enabled each polling cycle consists of two wetting current activation steps. The first step uses the
wetting current setting configured in the WC_CFG0 and WC_CFG1 registers as in the continuous mode or
polling mode. The second step (cleaning cycle) is activated simultaneously for all CCP enabled inputs at a time
t_{CCP_TRAN} after the normal polling step of the last enabled input. Interrupt generation and INT pin assertion is not
impacted by the clean current pulses.
The wetting current and its active time for the cleaning cycle can be configured in the CCP_CFG0 register. The
cleaning cycle can be disabled, if desired, for each individual input by programming the CCP_CFG1 register.
CCP is available for both continuous mode and polling mode. To use the CCP feature, at least one input has to
be enabled.
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