Scan method and topology for capacitive sensing
First Claim
Patent Images
1. A method of scanning capacitive sensors, comprising the steps of:
- sequentially connecting different sets of N capacitive sensor inputs to a common sense node, where N is an integer greater than 1, by activating switches that each couple one of the N capacitive sensor inputs to the common sense node; and
for each set of N capacitive sensor inputs, detecting if a capacitance at the N capacitive sensor inputs is within a predetermined range, includingproviding a charging current to the N capacitive sensor inputs, anddetermining if a time to charge the N capacitive sensor inputs is outside a predetermined timing range.
6 Assignments
0 Petitions
Accused Products
Abstract
A capacitive sensing system (100) can connect groups of capacitive sensors (112-1 to 112-N) to a common node (106) to detect change in capacitance. States of a set of capacitive sensors (112-1 to 112-N) can thus be scanned faster than approaches that scan such sensors one-by-one. Faster scanning can allow for reduced power consumption in applications that only periodically scan the set of capacitive sensors (112-1 to 112-N).
-
Citations
16 Claims
-
1. A method of scanning capacitive sensors, comprising the steps of:
-
sequentially connecting different sets of N capacitive sensor inputs to a common sense node, where N is an integer greater than 1, by activating switches that each couple one of the N capacitive sensor inputs to the common sense node; and for each set of N capacitive sensor inputs, detecting if a capacitance at the N capacitive sensor inputs is within a predetermined range, including providing a charging current to the N capacitive sensor inputs, and determining if a time to charge the N capacitive sensor inputs is outside a predetermined timing range. - View Dependent Claims (2, 3, 4)
-
-
5. A capacitive sensor scan system, comprising:
-
a plurality of switch devices that connect capacitive sensor inputs to a common node when enabled; a measuring circuit coupled to the common node that determines when the capacitance at the common node is outside of a predetermined range, the measuring circuit including an oscillator circuit that outputs a periodic signal that varies according the capacitance at the common node; and a switch controller that sequentially enables different sets of N switch devices essentially simultaneously. - View Dependent Claims (6, 7, 8, 9, 10, 11)
-
-
12. A capacitive sensing method, comprising:
-
in a scan operation coupling different sets of multiple capacitive sensor inputs to a common node; and for each set of capacitive sensor inputs, determining whether the capacitance at the common node is within a given range, including charging and discharging the common node within a given time period to generate a count value corresponding to the capacitance; and generating a sense indication if the capacitance is outside the given range. - View Dependent Claims (13, 14, 15, 16)
-
Specification