Cypress Semiconductor CY3280-MBR3 データシート

Document Number: 001-85330 Rev. *G 

Page 16 of 37

Note If more than one button is activated at the same time, the 

Rn becomes equivalent (parallel) to all Rn resistors.

■

For the circuit represented in 

 to work, GPOs should 

be configured in the Active LOW logic, open-drain drive mode. 

PWM must be disabled and the CSx-to-GPOx direct drive must 

be enabled (that is, GPOs must be configured as 

sensor-controlled).

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The FSS feature can be enabled so only one button is reported 

ON at a time.

System Diagnostics is a BIST feature that tests for faulty sensor, 

shield, or CMOD conditions at device resets.

■

If any sensor fails these tests, a 50-ms pulse is sent out on the 

corresponding GPO (that is, the pulse is observed on GPOx if 

CSx fails the test), and the sensor is disabled.

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If the shield fails the tests, a 50-ms pulse is sent out on all GPOs 

and all the sensors are disabled.

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If CMOD fails the tests, a 50-ms pulse is sent out on all GPOs 

and all the sensors are disabled.

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System Diagnostics failure pulses are sent within device 

boot-up time.

■

The System Diagnostics status is also updated in the 

. Therefore, the host can also read test results through the 

I

2

C interface.

If the parasitic capacitance of a sensor is more than 45 pF, the 

sensor is disabled.
Improper value of CMOD
If the value of CMOD is less than 1 nF or greater than 4 nF, all 

sensors are disabled (the recommended value of CMOD is 

2.2 nF).
Sensor shorts
System Diagnostics also checks for the following errors:

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Sensor shorted to V

ss

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Sensor shorted to V

DD

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Sensor shorted to another sensor

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Sensor shorted to shield