Datasheet

CY8CMBR3002, CY8CMBR3102
CY8CMBR3106S, CY8CMBR3108
CY8CMBR3110, CY8CMBR3116 Datasheet
Document Number: 001-85330 Rev. *G Page 25 of 37
Power Consumption and Operational States
The CY8CMBR3xxx family of controllers is designed with
multiple low-power operational states to meet the low-power
requirements of battery-powered applications. These controllers
have the following operational states (see Figure 16):
1. Boot: The devices load the last-known configuration data and
run system diagnostics tests.
2. Active: The sensors are scanned at a speed set by the refresh
interval to determine the presence of touch, proximity, or
finger position on a slider, and any configured outputs (GPOs,
buzzer, and HI
) are driven. The refresh interval can be
configured from 20 ms to 500 ms in steps of 20 ms, either
using the EZ-Click tool or by configuring the register.
3. Look-for-Touch: All the sensors are scanned at a much
slower, user-configured refresh interval, and any enabled
GPOs (such as PWM or DC Toggle) are driven.
4. Look-for-Proximity: Only proximity sensors enabled for
wake-on approach are scanned. No outputs are driven in this
state.
5. Deep Sleep: No sensors are scanned, and the
CY8CMBR3xxx devices are in a low-power state with no
processing. The GPO status is reset to the default value in the
Deep Sleep mode.
6. Configuration: No scanning or reporting occurs and the
devices wait for a reset for the configuration settings to take
effect.
The CY8CMBR3xxx controllers automatically manage
transitions between four operational states (Boot, Active,
Look-for-Touch, and Look-for-Proximity). The host can force
transition in and out of the Deep Sleep state. A host command
can alter the configuration data, causing a transition to the
Configuration state. A transition can also occur automatically
after boot.
The Active state emphasizes a high refresh rate (that is, low
refresh interval) for fast responses to button touches and
proximity events. The Look-for-Touch state enables low power
consumption during periods of no-touch activity.
The Look-for-Proximity state allows ultra-low power
consumption when a human body is not in close proximity. This
state is entered only if the wake-on-approach feature is enabled
(and the toggle is disabled). In this state, the CY8CMBR3xxx
controllers periodically scan proximity sensors to determine the
presence of a human body. If they detect human presence, the
controllers enter the Look-for-Touch state, in which they scan all
sensors at a slow, user-configured refresh interval. If a touch is
present, the controllers either enter or remain in the Active state,
in which they update the sensor status and drive the corre-
sponding outputs. A transition from Active to Look-for-Touch
occurs when no touch is detected and the buzzer is not driven.
Similarly, a transition from Look-for-Touch to Look-for-Proximity
occurs when no proximity is detected.
The following parameters configure the operational states:
■ State timeout (Register STATE_TIMEOUT) defines the
following:
❐ Minimum time (in seconds) of no touch activity in the Active
state
❐ Minimum time to trigger a transition to the Look-for-Touch
state
❐ Minimum time of no touch activity in the Look-for-Touch state
❐ Minimum time to trigger a transition to the Look-for-Proximity
state
■ Refresh Interval (Register REFRESH_CTRL) defines the
minimum time between the start of subsequent scans in the
Look for Touch and Look-for-Proximity states.
■ The Refresh Interval for the Active state is fixed at 20 ms.
During all three states—Active, Look-for-Touch, and
Look-for-Proximity—the devices enter standby mode after
scanning and processing the requisite sensors. This helps to
maintain the lowest power consumption within any refresh
interval.
The following guidelines result in the lowest operating current:
■ Ground all unused CapSense inputs (CSx)
■ Minimize C
P
■ Reduce CSx button sensitivity
■ Configure the design to be optimized for power consumption
■ Avoid using a high noise immunity level in a low-noise
environment
■ Use a higher Button Scan Rate or Deep Sleep operating mode