TIC10024-Q1 Datasheet, PDF (18/81 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
8.3.8.2 Input Enable Selection
The TIC10024-Q1 provides switch status monitoring for up to 24 inputs, but there might be circumstances in
which not all inputs need to be constantly monitored. The microcontroller may choose to enable/disable
monitoring of certain inputs by configuring the IN_EN register. Setting the corresponding bit to logic 0 de-
activates the wetting current source/sink and stops switch status monitoring for the input. Disabling monitoring of
unused inputs reduces overall power consumption of the device.
All inputs are disabled by default upon device reset.
8.3.8.3 Thresholds Adjustment
The threshold level for interrupt generation can be programmed by setting the THRES_COMP register. The
threshold level settings can be set for each individual input groups and each group consists of 4 inputs. Four
threshold levels are available: 2V, 2.7V, 3V, and 4V.
Caution should be used when setting up the threshold for switches that are connected externally to the battery as
there is a finite voltage drop (as high as V_{CSI_DROP_OPEN} for 10mA and 15mA settings) across the current sinks.
Therefore, even for an open switch, then voltage on the INx pin can be as high as V_{CSI_DROP_OPEN} and the
detection threshold shall be configured above it. It shall also be noted that a lower wetting current sink setting
might not be strong enough to pull the INx pin close to ground in the presence of a leaky open external switch,
as illustrated in the diagram below (see Figure 9). In this example, the external switch, although in the open
state, has large leakage current and can be modelled as an equivalent resistor (R_DIRT) of 5kΩ. The 2mA current
sink is only able to pull the INx pin voltage down to 4V, even if the switch is in the open state.
Battery- connected switch
+
14V
±
V_BAT
GND
RDIRT
5NŸ
RSW
Open
TIC10024-Q1
INx
2mA
GND
Copyright © 2016, Texas Instruments Incorporated
Figure 9. Example Showing The Calculation of The INx Pin Voltage For A Leaky Battery-Connected
Switch
8.3.8.4 Wetting Current Configuration
There are 6 different wetting current settings (0 mA, 1 mA, 2 mA, 5 mA, 10 mA, and 15mA) that can be
programmed by configuring the WC_CFG0 and WC_CFG1 registers. 0 mA is selected by default upon device
reset.
The accuracy of the wetting current has stronger dependency on the V_S voltage when V_S voltage is low. The
lower the V_S voltage falls, the more deviation on the wetting currents from their nominal values. Refer to I_WETT
(CSO) ^{and I}WETT (CSI) ^{specifications for more details.}
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