STV-376-E01(2008) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

STV-376-E01
(Rev.:2008)

Ultra-low power laser motion sensor for laser mouse applications

STMicroelectronics 

VT5376

Motion performance

1.2.2

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 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.

Figure 2.

Automatic power management

System is up and running (3 sub modes):

- low fram e rate (1K fps) for motion slower than 4ips

- medium frame rate (2Kfps) for motion between 4 and 8ips

- fast frame rate (4K fps) for motion faster than 8ips

No motion for 50ms

System wakes for

1 frame every 10ms

to check for motion

IDLE 1 MODE

RUN MODE

Motion detected

System wakes for

SLEEP M O DE 1 frame every 500ms

to check for motion

After 8 secs of IDLE 1 mode

IDLE 2 MODE

System wakes for

1 frame every 100ms

to check for motion

After 10 mins of IDLE 2 mode

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,

5/30

Share Link: