TIC10024-Q1 Datasheet, PDF (32/81 Pages) Texas Instruments – 24-Input Multiple Switch Detection Interface (MSDI) Device With Adjustable Wetting Current for Automotive Systems

TIC10024-Q1
SCPS268 – SEPTEMBER 2017
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Device Functional Modes (continued)
The wetting current is adjusted back to the original setting of 10 mA or 15 mA at a time of N cycles after an open
switch is detected, where N again depends on the DET_FILTER bit setting in the CONFIG register. Figure 22
depicts the behavior of the wetting current auto-scaling feature.
Switch open
Switch closed
Auto-scaling
disabled
0mA
15mA
Auto-scaling
enabled
0mA
15mA
2mA
Figure 22. Wetting Current Auto-scaling Behavior
The wetting current auto-scaling only applies to 10 mA and 15 mA settings and is only available in continuous
mode. If AUTO_SCALE_DIS_CSO or AUTO_SCALE_DIS_CSI bit is set to logic 1 in the WC_CFG1 registers,
the wetting current stays at its original setting when a closed switch is detected. Power dissipation needs to be
closely monitored when wetting current auto-scaling is disabled for multiple inputs as the device could heat up
quickly when high wetting current settings are used. If the auto-scaling feature is disabled in continuous mode,
the total power dissipation can be approximated using Equation 1.
P V u I I _TOTAL
S
S _ CONT WETT (TOTAL )
(1)
where I_{WETT (TOTAL)} is the sum of all wetting currents from all input channels. Increase in device junction
temperature can be calculated based on P × R_θJA. The junction temperature must be below T_TSD for proper
device operation. An interrupt will be issued when the junction temperature exceeds T_TW or T_TSD. For detailed
description of the temperature monitoring, please refer to sections Temperature Warning (TW) and Temperature
Shutdown (TSD).
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