Cypress CapSense CY8CMBR2044, Design Manual

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AN66308 - CY8CMBR2044 CapSense® Design Guide, Doc. No. 001-66308 Rev. *F 33
5. Low-Power Design Considerations
System Design Recommendations
Cypress’s CY8CMBR2044 is designed to meet the low-power requirements of battery powered applications.
To minimize power consumption, take these steps:

Ground all unused CapSense inputs

Minimize C
P
using the design guidelines in Getting Started with CapSense , Section 3.7.1.

Reduce supply voltage

Use a higher Button Scan Rate or Deep Sleep operating mode, refer to Button Scan Rate.
Calculating Average Power
The Design Toolbox , which is the tool of choice, automates the power consumption calculations described in the
following sections. The average power consumed by the CY8CBMR2044 is determined by calculating the parameters
below:
1. Button Scan rate, T
R
2. Scan time, T
S
3. Average current in a NO TOUCH state, I
AVE_NT
4. Average current in a TOUCH state, I
AVE_T
5. Average standalone current, I
AVE_SA
6. Average current, I
AVE
7. Average power, P
AVE
Button Scan Rate (T
R
)
Control the Button Scan rate though the external resistor connected to the ScanRate/Sleep pin of CY8CMBR2044.
The following equation provides the approximate scan rate:
Equation 5
Where:
R = value of external resistor (in ohms).
Refer to Table 3-4 to find the appropriate resistor value.
Response Time (T
RES
)
Selecting the Scan Rate means balancing the response time and power consumption requirements of your
application.