STV-376-E01 STMICROELECTRONICS [STMicroelectronics], STV-376-E01 Datasheet - Page 5

• Manufacturer Part Number: STV-376-E01
• Description: Ultra-low power laser motion sensor for laser mouse applications
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

VT5376
1.2.2
Figure 2.
System w akes for
1 fram e every 10m s
to check for m otion
After 8 secs of ID LE 1 m ode
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 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.
Automatic power management
The VT5376 automatic power management has a four state power scheme; RUN, IDLE1,
IDLE2 and SLEEP.
RUN mode is the mode where the whole system is up and running. This mode has three
sub-modes, 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,
N o m otion for 50m s
ID LE 1 M O D E
System is up and running (3 sub m odes):
- low fram e rate (1K fps) for m otion slower than 4ips
- m edium fram e rate (2Kfps) for m otion betw een 4 and 8ips
- fast fram e rate (4K fps) for m otion faster than 8ips
R U N M O D E
ID LE 2 M O D E
System wakes for
1 fram e every 100m s
to check for m otion
M otion detected
S LE E P M O D E
After 10 m ins of ID LE 2 m ode
System w akes for
1 fram e every 500m s
to check for m otion
Motion performance
5/30