vt5376 STMicroelectronics, vt5376 Datasheet - Page 5

• Manufacturer Part Number: vt5376
• Description: Ultra-low Power Laser Motion Sensor For Laser Mouse Applications
• Manufacturer: STMicroelectronics

VT5376
1.2.2
Figure 2.
Automatic power management via internal timer
In this mode, after having written the initialization I2C command, the POWERDOWN pin
must be left high at all times.
In running mode the motion engine operation is basically the same as above, however, in
the case no motion (after a set time) the chip now has the ability to put itself to sleep for a
determined period of time. This mode features the usual modes: RUNNING, IDLE1, IDLE2
and SLEEP, with on-chip preprogramming time constants (firmware).
In no motion it will in turn cycle to IDLE1/IDLE2 then SLEEP. In each of these modes, the
behavior is a single frame operation, the RC timer is programmed to wake up for next period
then the sensor goes to sleep.
The MOTION pin will go up if motion is ready for polling, here the sensor will remain in
RUNNING mode until the host has polled ALL motion data.
In this automatic power management mode the external MCU can set itself to STDBY and
just wait for the MOTION pin to come up, hence saving power in the no motion condition.
This enables application MCU firmware to be simplified as much as possible.
Automatic power management
The VT5376 automatic power management has a 4 state power scheme - RUN, IDLE1,
IDLE2 and SLEEP.
RUN mode is the mode where the whole system is up and running. This mode has 3 sub-
modes, dependant on the mouse velocity: 1K fps (for motion slower than 7 ips), 2K fps (for
motion between 7 ips and 14 ips) and 4K fps (for motion faster than 14 ips).
As long as there is motion the mouse will remain in this state.
After 5 0 ms of mouse inactivity the mouse goes into the IDLE 1 mode. In this mode the
system wakes up every 10 ms for 1 frame and checks for motion; if the mouse has not
moved the system automatically goes back to its low power state otherwise the system will
go into RUN mode.
After 8 secs of IDLE 1 mode, the system then goes into IDLE 2 mode where it wakes up for
1 frame every 100 ms. After 10 mins of no activity the system then falls into SLEEP mode,
which is exactly the same as the IDLE modes except that the system wakes up only every
500 ms to check motion activity.
System wakes for
1 frame every 10 ms
to check for motion
After 8 seconds of Idle 1 mode
No motion for 50 ms
IDLE1 mode
System is up and running (3 sub-modes):
- low frame rate (1K fps) for motion slower than 7 ips
- mediam frame rate (2K fps) for motion between 7 ips and 14 ips
- fast frame rate (4K fps) for motion faster than 14 ips
System wakes for
1 frame every 100 ms
to check for motion
RUN mode
IDLE 2 mode
Motion
detected
SLEEP mode
After 10 minutes of Idle 2 mode
System wakes for
1 frame every 500 ms
to check for motion
Motion performance
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