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| TIC12400-Q1 Datasheet, PDF (41/127 Pages) Texas Instruments – 24-Input Multiple Switch Detection Interface (MSDI) With Integrated ADC and Adjustable Wetting Current for Automotive Systems | |||
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www.ti.com
TIC12400-Q1
SCPS260 â AUGUST 2017
Figure 33 illustrates the operation of the CCP when the device is configured to the continuous mode:
Wetting
current
TRIGGER bit set
to logic 1 in
CONFIG register
tSTARTUP
IN0
IN1
ttADC or tCOMPt
IN2
IN22
IN23
ttPOLL_TIMEt
tSTARTUP
ttCCP_TIMEt
/INT
/CS
x Default input status is stored
x /INT pin is asserted after the
1st detection cycle
Read on INT_STAT register
release the /INT pin
Time
Figure 33. Continue Mode With CCP Enabled
8.4.3.2 Wetting Current Auto-Scaling
The 10 mA and 15 mA wetting current settings are useful to clean oxide build-up on the mechanical switch
contact surface when the switch changes state from open to close. After the switch is closed, it is undesirable to
keep the wetting current level at high level if only digital switches are monitored since it results in high current
consumption and could potentially heat up the device quickly if multiple inputs are monitored. The wetting current
auto-scaling feature helps mitigate this issue.
When enabled (AUTO_SCALE_DIS_CSO or AUTO_SCALE_DIS_CSI bit = logic 0 in the WC_CFG1 register),
wetting current is reduced to 2 mA from 10 mA or 15 mA setting after switch closure is detected. The threshold
used to determine a switch closure is the threshold configured in the THRES_COMP register for inputs
configured as comparator input mode. For inputs configured as ADC input mode, the threshold used to
determine a switch closure depends on the input number, as described in Table 8 below.
Table 8. Threshold Used To Determine A Switch Closure For Wetting Current Auto-scaling For ADC
Inputs
INPUT
IN0-IN11
IN12 to IN17
IN18 to IN22
IN23
THRESHOLD USED TO DETERMINE A SWITCH CLOSURE
Mapped threshold from THRES0 to THRES7
THRES2B
THRES3C
THRES9
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