VT5376 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
VT5376 Datasheet PDF : 31 Pages
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VT5376
Motion performance
1.2.2
Automatic power management using the 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 the manual power
management mode, however, in the case of 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 preprogrammed time constants
(firmware).
If no motion is detected the VT5376 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 the next period then the sensor goes to sleep. The MOTION pin will go high if motion
is detected. The sensor will remain in RUN 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 the application MCU firmware to be simplified as much as possible.
The VT5376 automatic power management has a four state power scheme; RUN, IDLE1,
IDLE2 and SLEEP, see Figure 1.
Figure 1.
Automatic power management
System is up and running (3 submodes):
- low frame rate (1 Kfps) for motion slower than 4 ips
- medium frame rate (2 Kfps) for motion between 4 and 8 ips
- fast frame rate (4 Kfps) for motion faster than 8 ips
No motion for 50 ms
RUN mode
System wakes for
1 frame every 10 ms IDLE 1 mode
to check for motion
Motion detected
System wakes for
SLEEP mode 1 frame every 500 ms
to check for motion
After 8 secs of IDLE 1 mode
IDLE 2 mode
After 10 mins of IDLE 2 mode
System wakes for
1 frame every 100 ms
to check for motion
RUN mode is the mode where the whole system is up and running. This mode has three
submodes, dependant on the mouse velocity: 1K fps (for motion slower than 4 ips), 2K fps
(for motion between 4 ips and 8 ips) and 4K fps (for motion faster than 8 ips).
As long as there is motion the mouse will remain in this state.
After 50 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 seconds of IDLE 1 mode, the system then goes into IDLE 2 mode where it wakes up
for 1 frame every 100 ms. After 10 minutes of no activity the system falls into SLEEP mode,
Doc ID 13939 Rev 4
5/31
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