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VT5376
Ultra-low power laser motion sensor for laser mouse applications
Preliminary Data
Features
Figure 1.
Single battery
Application block diagram
VTOP (>=2.2V)
Ultra-low power performance and high speed/high accuracy motion detection (1 m/s, 20 g) Optional on-chip power management scheme (RUN/IDLE1/IDLE2/SLEEP) On-chip boost-converter controller enables a complete autonomous single AA/AAA-type battery supply application Very low quiescent and operating current mode for battery life saving I2C interface, with fast polling rate capability for high end applications (report rate up to 1 per ms) Internal oscillator CPI programmable up to 3200 CPI On-chip ADC for battery level reporting Laser drive circuitry, fault detection scheme and safety features Versatile usage: the sensor is designed to operate with a companion microcontroller, and can be used for any laser/LED mouse system although it is optimized for wireless applications (27 MHz/2.4 GHz/BT). RoHS (lead-free) package

AVDD DVDD VREG VBat
VREF
VGATE Start VGATE On VTOP

VT5376
RBIN RC_OSC Vtop

Laser Out
ResetOut SDA SCL Power Down Motion Laser NEN Vtop
MCU
RF module / USB
Buttons Scroll Wheel Tilt Wheel
Applications

Ultra-low power wireless laser mouse, 27 MHz, 2.4 GHz and Bluetooth Also suitable for laser USB mouse applications
Description
This device is intended to fit into any 2-chip applications (companion MCU) and offers the best compromise between application cost, power and performance.
September 2008
Rev 2
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www.st.com 30
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
Contents
VT5376
Contents
1 Motion performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 1.2 Technical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Battery life management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 1.2.2 Manual power management via POWERDOWN pin . . . . . . . . . . . . . . . . 4 Automatic power management via internal timer . . . . . . . . . . . . . . . . . . . 5
2
Power supply options and power consumption . . . . . . . . . . . . . . . . . . . 7
2.1 2.2 Low cost application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 External supply application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1 3.2 3.3 Supply voltages (using internal DC/DC controller) . . . . . . . . . . . . . . . . . . . 8 Supply voltages (direct drive, bypassing DC/DC controller) . . . . . . . . . . . . 8 Logic IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4
Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1 4.2 4.3 4.4 Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Message interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Type of messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 6
I2C control register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Laser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1 6.2 6.3 Direct laser drive and calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Laser or led system managed by host (external micro) . . . . . . . . . . . . . . 18 Laser fault detection and safety feature . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7
General features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1 7.2 7.3 7.4 Device clocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Battery level monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Resolution setting (counts/inch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Image (frame) capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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VT5376
Contents
7.5 7.6 7.7
Image streaming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Optical centre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Sensor orientation on PCB (with lens) . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8
Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1 Overall 2.4 GHz mouse power consumption example . . . . . . . . . . . . . . . 24
9
Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
10
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
10.1 TQFP package guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11 12
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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Motion performance
VT5376
1
Motion performance
The sensor can operate with a VCSEL or LED (visible and IR), and when bundled with the appropriate optics subsystem is able to track motion on a wide range of surfaces up to speeds of 1 m/s (40 ips), and to detect acceleration of up to 20 g. The sensor achieves this top speed with very low drift and high accuracy.
Note:
Although this device features an UltraLowPower motion detection machine, the power saving has not been achieved by compromising tracking accuracy.
1.1
Technical specifications
Table 1. Technical specifications
Parameter Resolution Pixel size Array size Frame rate Tracking performances Supply voltage Operating temperature Package type Description Programmable up to 3200 CPI 30.4m 20*20 pixels up to 4000 fps Laser or LED: 1m/s Very low drift. 1 V to 1.6 V (1) 0C to 60C 7 mm x 7 mm x 1.4 mm 32 lead LOQFP (Low profile Optical Quad Flat Pack)
1. Using internal boost converter controller. Otherwise, voltage supply ranges from 1.7V to 1.9V.
1.2
Battery life management
The battery life management (in no motion state) can be done manually where the external MCU is the master and controls the sensor state via its POWERDOWN pin (default mode). Alternatively, the sensor can manage its own power states. In no motion, it cycles through IDLE and SLEEP modes automatically without any intervention from the MCU. Therefore by using the sensor's automatic power management, the MCU can be fully switched OFF in the case of no motion allowing for extra power savings, and resulting in a very simple driver firmware design.
1.2.1
Manual power management via POWERDOWN pin
In this mode the chip is woken-up by de-asserting the POWERDOWN pin. When doing so both the analog and DCDC engines are woken up in a programmed sequence. The POWERDOWN pin can be re-asserted straight away as the sensor undergoes just a single frame sequence.
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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 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
RUN MODE
N o m otion for 50m s M otion detected
System w akes for 1 fram e every 10m s to check for m otion
ID LE 1 M O D E
S LE E P M O D E
System w akes for 1 fram e every 500m s to check for m otion
After 8 secs of ID LE 1 m ode
After 10 m ins of ID LE 2 m ode
ID LE 2 M O D E
System wakes for 1 fram e every 100m s to check for m otion
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,
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Motion performance
VT5376
which is exactly the same as the IDLE modes except that the system wakes up only every 500 ms to check motion activity.
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VT5376
Power supply options and power consumption
2
Power supply options and power consumption
The sensor includes a DCDC controller to supply the laser / LED. This allows the overall sensor system to operate from a single AA or AAA battery supply voltage (from 1.6V down to 1V), allowing for a simple and low power / low cost system design. Two power supply schemes can be used.
2.1
Low cost application
The internal DCDC controller and voltage regulators are used so that the overall application can be supplied from a single AA/AAA battery cell, without the need for an external step-up convertor device. This approach is extremely economical.
Table 2.
Typical power supply and power consumption
Run IDLE1 4000 fps 2000 fps 3.5 mA 0.04 mA 1000 fps 2.4 mA 0.04 mA 0.3 mA 0.04 mA 0.15 mA 0.04 mA 0.1 mA 0.04 mA IDLE2 SLEEP
Total @ ITop (chip + Laser/LED) Total chip @Vbat
5.8 mA 0.04 mA
Note:
1 2
DCDC efficiency from single battery cell to Vtop (typical 2.2V) is around 70%. Maximum load on Vtop is 25mA
2.2
External supply application
In this instance, the internal DCDC controller and voltage regulators are turned off and bypassed. The sensor then needs to be supplied with a single regulated 1.8V +/- 0.1V.
Table 3.
Power supply and typical power consumption
Run IDLE1 4000 fps 2000 fps 1000 fps IDLE2 SLEEP
Total @Vtop/Vbat/Dvdd/ Avdd (1.8V) Chip + Laser/LED
5.8 mA
3.5 mA
2.4 mA
0.3 mA
0.15 mA
0.1 mA
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Electrical characteristics
VT5376
3
3.1
Electrical characteristics
Supply voltages (using internal DC/DC controller)
Table 4.
Symbol VTOP VBAT Boosted
Supply voltages using DC/DC controller
Parameter supply(1) Min. 2.0 1.0 Typ. 2.2 1.25 Max. 2.6 1.6 Unit V V
Supply from single AA cell
1. Value defined by resistors ratio
3.2
Supply voltages (direct drive, bypassing DC/DC controller)
Table 5.
Symbol VTOP VBAT AVDD DVDD VREG
Supply voltage values (direct drive, bypassing DC/DC controller)
Parameter Boosted supply Supply from single AA cell Analog supply Digital core supply Digital core supply Min. 1.7 1.0 1.7 1.7 1.7 Typ. 1.8 1.8 1.8 1.8 1.8 Max. 1.9 1.9 1.9 1.9 1.9 Unit V V V V V
3.3
Logic IO
Table 6.
Symbol
Digital IO electrical characteristics
Parameter Min. Typ. Max. Unit
CMOS digital inputs (Reset_Out, Motion, PowerDown, SDA and SCL) VIL VIH IIL IIH Low level input voltage High level input voltage Low level input current High level input current 0 0.7*VDD 0.3*VDD VDD + 0.3 -1 1 V V A A
CMOS digital outputs VOL VOH Low level output voltage (4mA load) High level output voltage (4mA load) 0.7*VDD 0.3*VDD V V
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VT5376
Interface
4
Interface
The interface is 400 kHz I2C, with very fast polling rate for high CPI applications (down to 1 ms period).
4.1
Protocol
Figure 3. Serial interface data transfer protocol
Acknowledge
Start condition
SDA MSB SCL S 1 2 3 4 5 6 7 LSB 8 P A Stop condition
Address or data byte
4.2
Data format
Information is packed in 8-bit packets (bytes) always followed by an acknowledge bit. The internal data is produced by sampling sda at a rising edge of scl. The external data must be stable during the high period of scl. The exceptions to this are start (S) or stop (P) conditions when sda falls or rises respectively, while scl is high. The first byte contains the device address byte which includes the data direction read, (r), ~write, (~w), bit. Figure 4. VT5376 serial interface address
0
0
1
0
0
0
0
R/W
The byte following the address byte contains the address of the first data byte (also referred to as the index).
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Interface
VT5376
4.3
Message interpretation
All serial interface communications with the sensor must begin with a start condition. If the start condition is followed by a valid address byte then further communications can take place. The sensor will acknowledge the receipt of a valid address by driving the sda wire low. The state of the read/~write bit (lsb of the address byte) is stored and the next byte of data, sampled from sda, can be interpreted. During a write sequence the second byte received is an address index and is used to point to one of the internal registers. The serial interface will automatically increment the index address by one location after each slave acknowledge. The master can therefore send data bytes continuously to the slave until the slave fails to provide an acknowledge or the master terminates the write communication with a stop condition or sends a repeated start, (Sr). As data is received by the slave it is written bit by bit to a serial/parallel register. After each data byte has been received by the slave, an acknowledge is generated, the data is then stored in the internal register addressed by the current index. During a read message, the content of the addressed register is then parallel loaded into the serial/parallel register and clocked out of the device by scl. At the end of each byte, in both read and write message sequences, an acknowledge is issued by the receiving device. A message can only be terminated by the bus master, either by issuing a stop condition, a repeated start condition or by a negative acknowledge (NAck) after reading a complete byte during a read operation.
4.4
Type of messages
Single location, single data write
When a random value is written to the sensor, the message will look like this: Figure 5. Single location, single write
Start
Device address
Ack
Index
Data
Stop
S
20h
A
07h
A
00h
A
P
The r/w bit is set to zero for writing. The write message is terminated with a stop condition from the master.
Single location read
When a location is to be read, but the value of the stored index is not known, a write message with no data byte must be written first, specifying the index. The read message then completes the message sequence. To avoid relinquishing the serial to bus to another master a repeated start condition is asserted between the write and read messages.
10/30
VT5376 Figure 6. Single read
No data write S 20h A 20h A Sr 21h A Read data 15 A P
Interface
NAck from the master
As mentioned in the previous example, the read message is terminated with a negative acknowledge (A) from the master.
Multiple location write
It is possible to write data bytes to consecutive adjacent internal registers without having to send explicit indexes prior to sending each data byte. Note: An auto-increment write is assumed if no stop condition occurs. Figure 7. Multiple location write
Incremental write S 20h A 07h A 11 A C1 A P
data written @ index = 07
data written @ index = 08
Multiple location read: reading motion value example
Multiple locations can be read within a single read message. An auto-increment write is assumed. Note: Registers are read until the master Nacks the data. Figure 8. Multiple location read: reading motion
No data write S 20h A 21h A Sr 21h A Incremental read Xmotion A Ymotion AP
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I2C control register map
VT5376
5
Table 7.
Address 0x00
I2C control register map
I2C control register map
Bits [7:0] Name Device Hardware revision R/W RO Default 00h Description HW revision: set by the mask set revision FW revision: is updated every time internal firmware of minor revision is done. When set, the device controls its own power mode state machine in no motion condition. If not set, POWERDOWN controls the state of the device (standby/run) When set, the device sets all internal variables to optimize the system for laser illumination. If set, LASER_OUT is actived to direct drive a VCSEL, and LASER_NEN controls its power supply switch. If not set, LASER_NEN becomes the LED_ON signal, toggling at frame rate. 1: The device switches its internal 1.8 V regulator off, and assumes 1.8 V will be supplied at all times to Vtop, DVDD and AVDD. VBat can also be supplied by the same 1.8V or from a single battery. 0: Device uses internal regulators (Vtop must be set >= 2.2V). This bit must be set to 1 to indicate to the chip that the boot configuration of the sensor (mainly this register) is complete, and it can start motioning. If set to 1, and the chip is set in LED mode, then the LED is direct driven by the internal DAC. If enabled the MCU firmware will go into an idle mode (I2C commands still available).
0x01
[7:0]
Device Soft revision
RW
01h
[0]
Automatic Power management
RW
0h
[1]
Laser Selected
RW
0h
0x05 [2] Use External Supply RW 0h
[3]
Host Config Done
RW
0h
[5]
Led dac driven
RW
0h
[7]
fw idle state
RW
0h
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VT5376 Table 7.
Address
I2C control register map I2C control register map (continued)
Bits Name R/W Default Description If set to 1, this sets the LASER_OUT DAC always ON (instead of toggling normally). This mode is provided in case the DAC current needs calibrating. To confirm this mode, register 0x0D will also need to be written to (complement data). Sets DAC current setting. To validate the setting, register 0x0D will also need to be written to (complement data). With Rbin = 12K ohms, 0x7F: 3.4mA 0x00: 10mA. 0: Current source OFF 1: Enable current source Laser NEN pin state Note: This command is only valid if bit [5] is 1 0: LASER_NEN 1.8V capable CMOS 1: LASER_NEN - OpenDrain 5V tolerant Note: This command is only valid if bit [5] is 1 0: Normal operation, LASEROUT set by DAC 1: Set to 1 to detect short to GND on LASER_OUT 0: Disable fault detection comparators 1: Enable fault detection comparators 0: LASER_NEN replaced by TRK_LED pulse (LED) 1: LASER_NEN controlled by bits [1] and [2] (Laser) 0: Disable bias current source 1: Enable bias current source Note: valid only if bit [7] is high 0 : Laser bias is driven the same way as laser drive (DAC) 1 : Laser bias is controlled with laser_bias_enable signal (bit [6])
[7]
Force Laser Out ON
RW
0h
0x0A
[6:0]
DAC current setting
RW
7Fh
[0]
Laser Drive Enable
RW
0h
[1]
Laser NEN Out
RW
1h
[2]
Laser NEN OD Enable
RW
1h
[3] 0x0B [4]
Force Laser Out High
RW
0h
Laser comp Enable
RW
0h
[5]
Laser NEN trk led n
RW
0h
[6]
Laser Bias Enable
RW
0h
[7]
Laser Bias Ctrl
RW
0h
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I2C control register map Table 7.
Address
VT5376
I2C control register map (continued)
Bits Name R/W Default Description 0: Rbin above threshold 1: Rbin below threshold (shorted to GND) Note: if Laser_Comp_Enable (reg 0x0B, bit [4]) = 0, Rbin_Low=1 0: Laser OUT above LOW threshold 1: Laser OUT below LOW threshold (shorted to GND). Note: if Laser_Comp_Enable = 0, Laser_Low = 1 0: Laser OUT below HIGH threshold 1: Laser OUT above HIGH threshold (shorted to VDD). Note: if Laser_Comp_Enable = 0, Laser_High = 1 If set to 0, this sets the LASER_OUT DAC always ON (instead of toggling normally). This mode is provided in case the DAC current needs calibrating. To confirm this mode, register 0x0A will also need to be written to (complement data). Sets DAC current setting. To validate the setting, register 0x0A will also need to be written to (complement data). With Rbin = 12K ohms, 0x00: 3.4mA 0x7F: 10mA This register holds the overall X movement data since last polling was done. Value is 8 bit 2's complement.(1) This register holds the overall Y movement data since last polling was done. Value is 8 bit 2's complement.(1) 0h 0h 0h This register records if the X-motion integrator has reached its limit. This register records if the Y-motion integrator has reached its limit. This bit is asserted if both X/Y integrators are empty
[5]
Rbin Low
RO
0h
0x0C
[6]
Laser Low
RO
0h
[7]
Laser High
RO
0h
[7]
Force Laser Out ON (Compl)
RW
1h
0x0D
[6:0]
DAC current setting (Compl)
RW
00h
0x21
[7:0]
X_motion
RO
0x22
[7:0]
Y_motion
RO
[0] 0x23 [1] [3]
X Overflow Y Overflow No Motion
RO RO RO
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VT5376 Table 7.
Address
I2C control register map I2C control register map (continued)
Bits [0] [1] [3] Invert X Invert Y Swap XY Test Pattern Enabled Name R/W RW RW RW RW Default 0h 0h 1h 0h Description Allows X to be inverted (2) Allows Y to be inverted(2) Replaces X with Y and Y with X 0: Normal mode 1: Diamond shape pattern Diamond test pattern speed 0x0 : motion = 127 max speed 0x1 : motion = 64 0x2 : motion = 32 0x3 : motion = 16
0x27
[5]
[7]
Test Pattern Speed
RW
0h
0x29
[7:0]
Min_features[13:6]
RW
This register represents the feature threshold below which motion is no longer valid (in this case, the device 0000_0100 reports "0" motion). This is linked to the value reported in registers 0x31/0x32 Sets resolution as CPI: 8: 400 CPI 0001_0000 16: 800 CPI Assuming lens magnification of x0.5 Sets resolution as CPI: 0x08: 400 CPI 0001_0000 0x10: 800 CPI Assuming lens magnification of x 0.5 Feature count report: the higher the value, the more distinctive features the surface requires, for the motion detection machine to operate reliably. 80h 1h Exposure value in 2 x CLK12 period units Auto exposure enable This register holds the current converted data from the Vbat input voltage. The data range is as follows: 0000_0000: Vbat = 0.6 V 1111_1111: Vbat = 1.6 V The response is linear for each value in between. ADC step: 1V/256 = 3.9mV This registers holds the maximum pixel value (before CDS) for the current frame. It shows if some pixels are saturated or not.
0x2A
[7:0]
Scaling for X motion vectors
RW
0x2B
[7:0]
Scaling for Y motion vectors
RW
0x31 0x32 0x41 0x43
[15:8] Features count [7:0] [7:0] [4] Exposure [8:1] Auto Expo En
RO RO RW RW
0x47
[7:0]
Vbat converted data
RO
0x4F
[7:0]
Exp max value
RO
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I2C control register map Table 7.
Address
VT5376
I2C control register map (continued)
Bits Name R/W Default Description This register contains the pixel value when the frame dump feature has been activated (reg 0x62, bit 0). To read the 400 pixels from the captured frame, the register must be read 400 consecutive times. If set to 1, the device will capture a single frame. When the frame is captured and ready to be downloaded via reg 0x61, bit 2 (frame ready) is set. Bit is set at start of frame dump This bit is asserted when the captured frame is ready to be downloaded via reg 0x61. When frame download is complete, bit 3 is reset This flag is set when all 400 pixels have been read by I2C host. If set Motion, Laser_NEN, Reset_Out and VGate_On become PCI data ouptuts (QCLK, FST and 2 bits serial data) Timer interrupt enable.
0x61
[7:0]
IMAGE[7:0]
RO
[0]
Frame dump mode enable
RW
0h
[1]
Frame dump start
0h
0x62
[2]
Frame ready for download
RO
0h
[3]
Frame upload complete
0h
[4]
PCI Test enable
R/W
0h
0x82
[1]
Timer ITR enable
R/W
1h
1. Internal ACCUMULATOR is reduced from this value every time it is read. 2. Default changes to 1 for a laser system after host_config_done (that is, system set up for optics without a lens)
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VT5376
Laser
6
6.1
Laser
Direct laser drive and calibration
The sensor includes a 7-bit DAC and an output current source. The DAC value must be set via two I2C commands after power-up (default is MIN = 3.4mA, with Rbin = 12K). To allow VCSEL output power measurements to be done, the user can set the laser out (normally strobed during operation) to continuously on via an I2C command. This feature is optional and is designed to offer maximum flexibility. Alternatively, the Idac maximum (up to a max = 13mA) and minimum values can be changed by adjusting the Rbin value (for example, with Rbin = 24K, Idac max = 5mA and Idac min = 1.7mA). Idac max is set by the formula: Idac (max) = 120/Rbin (result in mA, Rbin in kohms) No external driver is required, just a FET power switch controlled by LASER_NEN signal.
Figure 9.
Application schematics using Laser or LED (driven with internal DAC or external current source)
LED system driven by internal DAC LED system driven by external drive
laser_selected = 0 led_dac_driven = 1 VTOP VTOP laser_select = 0 led_dac_driven = 0 36X trk_led (active high) VTOP
Laser system driven by internal DAC
laser_selected = 1
LASER_NEN laser LASER_OUT
LASER_NEN LED LASER_OUT
LASER_NEN
LED
LASER_OUT
RBIN
RBIN
RBIN
VT5376
VT5376
VT5376
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Laser
VT5376
6.2
Laser or led system managed by host (external micro)
The host must first select LED or LASER (bit [1] of register 0x05).
LED The host must select if the LED is to be driven by the internal DAC or an external current supply using bit [5] of register 0x05 (led_dac_driven). Bit [3] of register 0x05 (host_config_done) then needs to be set. - - Case internal DAC drive: VT5376 sets the maximum current from the DAC and the system starts running. Case external drive: VT5376 powers down its laser_drive and the led_on signal is present on the LASER_NEN pin.
LASER The host must first decide whether to perform LASER fault detection (described in Section 6.3) then set bit [3] of register 0x05 (host_config_done). If the system passes the laser fault detection (or laser fault detect was not performed), the host can then adjust the LASER DAC current by writing a value to bits [0-6] in register 0x0A AND writing its complementary value to bits [0-6] of register 0x0D, if the values are not compatible the VT5376 applies the minimum DAC current.
6.3
Laser fault detection and safety feature
The sensor includes a set of diagnostic features that can be carried out at power-up (before setting host_config_done). The tests listed below can be selected.
Check LASER_OUT is not shorted to VDD (LASER_OUT < 1.2V). - Enable DAC and disable OUT_HIGH switch by writing 0xF7 to register 0x0B (Top_ laser_setting), then make force_laser_out_on = 1, by writing 0x01 to bit 7 of register 0x0A (Top_laser_DAC_setting), and 0 to it's complementary bit (bit 7) in register 0x0D (Top_laser_Dac_setting_C). Finally read bit 6 of register 0xC to ensure that laser_low = 1. External LASER_NEN switch must be fitted in order to make LASER_OUT go below 0.4V.
Check LASER_OUT and RBIN are not shorted to GND (LASER_OUT and RBIN > 0.4V). - Disable DAC and enable OUT_HIGH switch (force_laser_out_high = 1) by writing 0xFE to register 0x0B (Top_laser_setting). Then read register 0x0C (Top_laser_diagnostics) to ensure that bit 7 (laser_high) is set to 1 and bit 5 (Rbin_low) is set to 0.
If the result of these tests is a pass then the MCU can set the laser system as follows: 1. 2. 3. Set bit [3] of register 0x05 (host_config_done). Write 0x25 (laser_drive and laser_nen enable) in register 0x0B (Top_laser_setting). Write the required DAC value (bits 0-6) in register 0x0A (Top_laser_DAC_setting) ensuring that force_laser_out_on = 0. Write the 1's complement value of the above setting in register 0x0D (Top_laser_Dac_setting_C).
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VT5376
General features
7
7.1
General features
Device clocking
The device integrates its own oscillator. It does not require an external Xtal or resonator, instead it requires only an external capacitor of 33 pF. The accuracy of this cap will determine the accuracy of the internal clock. Ignoring the capacitor accuracy, the frequency will be accurate within 10% range.
7.2
Battery level monitoring
The device includes an 8-bit ADC that translates the VBAT voltage into an 8-bit value that can be read via I2C. The external MCU can upload this value and take any action required.
7.3
Resolution setting (counts/inch)
Due to an accurate on-chip interpolation process, the device operates below the pixel resolution. This enables the user to easily select any desired resolution via a simple register write.
Note:
Different resolutions can be applied to X and Y. This could be useful in case of optical non-symmetry or distortion.
7.4
Image (frame) capture
It is possible to capture an image and download it using a simple I2C write/read sequence. This is useful to calibrate optics during pre-production or to perform basic tests. In order to achieve this, the user must: 1. 2. 3. Put the firmware into IDLE by setting bit 7 of register 0x05 (fw_idle_state). Disable the motion engine controller by clearing bit 1 of register 0x82 (timer_itr_enable). Enable frame dump mode by setting bit 0 of register 0x62 (frame_dump_mode_enable).
The VT5376 resets the sensor, enables the DCDC, runs a single frame sequence and stores it into an internal RAM. Once this process is complete, the VT5376 signals that the image is ready for download, by asserting bit 2 in register 0x62 (frame_ready_for_download). When this flag is asserted, the user can download the 400 consecutive pixels by reading register 0x61 (image) 400 consecutive times. When all the pixels have been read, the VT5376 signals the end of the process by setting bit 3 in register 0x62 (frame_upload_complete). To resume normal operation the user should reset bit 0 in register 0x62 to exit the frame dump mode, take the firmware out of Idle by resetting bit 7 of register 0x05 and set bit 1 of register 0x82 to enable the motion controller.
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General features Figure 10. Frame dump mode timing diagram
VT5376
400 x I2C single reads of pixel data set by user set by 376 set by 376 reset by user
frame_dump_en
frame_dump_ready
frame_dump_pixel
0
1
2
3
398
399
pixel address
frame_dump_completed NORMAL MODE FRAME DUMP MODE NORMAL MODE
7.5
Image streaming
To enter this test mode, set bit 4 of registry 0x62 to 1 (PCI_test_enable). In this mode, the pins VGATE_ON, RESET_OUT, LASER_NEN and MOTION are used to output serially fast video data in the form of 2 bits nibble + FST and QCLK. Upon receipt of an FST (LASER_NEN) rising edge, NIB_EVEN (VGATE_ON) and NIB_ODD (RESET_OUT) output data every 48 MHz clock cycle. The signals should be sampled 10 ns after the FST rising edge, and then every 20.8 ns exactly, during 400 x 4 = 1600 cycles. Groups of four consecutive NIB_EVEN and NIB_ODD must then be repackaged together to form a single 8-bit pixel data. This format enables the pixels to be output at the same frame rate as normal operation, and keeps I2C available to access the usual register settings. For more details on image streaming please refer to the VT5376 image system user manual.
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VT5376 Figure 11. Image streaming timing diagram
General features
Motion (48MHz QCLK)
Laser_NEN (FST)
VGate_On (NIB_EVEN) Reset_Out (NIB_ODD)
64 75
20 31
reconstructed pixel data
pixel_0[7:0] pixel_1[7:0]
pixel_399[7:0]
7.6
Optical centre
The optical centre of the VT5376 is NOT in the centre of the package. It is offset by -0.232 mm in the X axis and +0.217 mm in the Y axis with respect to the centre of the package as shown in Figure 12. The PCB designer must take this into account when laying out the PCB. Figure 12. VT5376 optical centre
Optical centre (-0.232mm, +0.217mm) Pin 1 marking
mechanical centre of package (0,0)
TOP VIEW OF VT5376
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General features
VT5376
7.7
Sensor orientation on PCB (with lens)
The VT5376 must be orientated correctly on the PCB in order to move the cursor in the correct directions when the mouse is moved. This is shown in Figure 13. Figure 13. VT5376 optical centre
UP
Pin 1 marking
LEFT
RIGHT
VT5376 mounted UNDERNEATH TOP VIEW of PCB DOWN
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VT5376
Typical application
8
Typical application
Figure 14. Very low power and low cost wireless laser application
VTOP (>=2.2V) 1.8V 1.8V max load = 25mA
TEST_CLOCK
VREG
VTOP
1 AVSS AVDD
DVSS1
VGATE_ON VREF VBAT VGATE_START VTOP LASER_OUT RBIN LASER_NEN
MOTION
VT5376
RC_OSC DVSS2 DVDD2 RESET_OUT 1.8V
PDN* SDA SCL
RF module
MCU
BT or 2.4 GHz prop
1 AA
Low Batt
buttons/scroll wheel/tilt wheel
PDN* = POWER_DOWN
resolution setting switches display
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Typical application
VT5376
8.1
Overall 2.4 GHz mouse power consumption example
Assumptions

VCSEL, MCU and 2.4 GHz Tx operate from 2.2 V MCU consumes 1 mA in running mode and 50 uA in standby mode. In no motion period, it remains in standby until it receives an interrupt from the VT5376, indicating that MOTION has been detected. 2.4 GHz Tx consumes 10 mA, but data is sent by bursts of 500 s every 5 ms (that is Nordic nRF2402). Maximum current is delivered to VCSEL (10 mA strobed). DCDC efficiency is 70% Ambient temperature

Table 8.
Power supply and typical power consumption
Run IDLE1 4000 fps 2000 fps 12 mA 1000 fps 9.3 mA 0.59 mA 0.29 mA 0.24 mA IDLE2 SLEEP
Total @Vbat (1.25 V)
18 mA
Using STMicroelectronics battery life model, these values would enable the mouse to operate for 12 months from two AA batteries in parallel.
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VT5376
Pinout
9
Pinout
Figure 15. Pinout
VREG
TEST_CLOCK
VTOP
1
AVSS AVDD VGATE_ON VREF VBAT
POWERDOWN
DVSS1
SDA SCL
MOTION VT5376 RC_OSC DVSS2 DVDD2 RESET_OUT
VGATE_START LASER_OUT RBIN LASER_NEN
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Pinout
VT5376
9.1
Table 9.
Pin 1 2 3 4 5 6 7 8 17 18 19 20 21 22 23 25 26 28 29 31 32
Pin description
VT5376 pin description
Pin name AVDD VGATE_ON VREF VBAT VGATE_START LASER_OUT RBIN LASER_NEN RESET_OUT DVDD2 DVSS2 RC_OSC MOTION SCL SDA POWERDOWN TEST_CLOCK VTOP VREG DVSS1 AVSS Type PWR I/O ANA PWR ANA ANA ANA I/O I/O PWR PWR ANA I/O I/O I/O I/O I/O PWR PWR PWR PWR Description 1.8 V regulated and analog supply Digital IO Analog ref input Single battery supply Output Laser drive set by internal DAC Sets maximum laser/led current Laser enable Digital IO 1.8 V regulated and digital supply Digital Ground 6 MHz Oscillator Digital IO Digital IO Digital IO Digital IO Digital IO Power supply for internal regulators 1.8 V regulated supply Digital ground Analog ground Connect 33pF to ground 1.8V only 5V tolerant 5V tolerant Active high Connect to ground int DCDC: 2.0 V to 2.6 V Ext: 1.8 V +/-0.1 V Connect to DVDD/AVDD Typical 12K ohms Active low 1.8V only Connect to VREG Comment Connect to VREG/DVDD Supplied by VTOP To set VTOP int DCDC: 1.0 V to 1.6 V ext: 1.0 V to 1.9 V Supplied by Vbat
Note:
All other pins are NOT CONNECTED.
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VT5376
Package mechanical data
10
Package mechanical data
Figure 16. TQFP32 clear resin body 7.0 x 7.0 x 1.40 footprint 1.0
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Package mechanical data Table 10. TQFP dimensions (mm)
Minimum (mm) Typical (mm)
VT5376
Reference A A1 A2 B c D D1 D3 e E E1 E3 L L1 k W1 W2
Maximum (mm) 1.600
0.050 1.350 0.300 0.090 9.000 7.000 5.600 0.800 9.000 7.000 5.600 0.450 0.600 1.000 0d 3.5d 5.000 0.650 1.400 0.370
0.150 1.450 0.450 0.200
0.750
7d
Note:
1 2 3
Surface finish W1 is 0.07 Ra. Ejectors are on 5.2 mm square for both top and bottom package. On top package, only the pin 1 identification is not an engraved ejector.
10.1
TQFP package guidelines
The IC can be exposed a maximum of two times to an IR/Convection reflow solder process having a temperature profile peak of no higher than 240 C. The package/chip are lead free and is ROHS compliant. For full handling guidelines please contact ST (document reference 7310263).
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VT5376
Ordering information
11
Ordering information
Table 11. Ordering information
Package TQFP32 OPTO 7 mm x 7 mm x 1.4 mm Packing Tray
Order code VT5376V032
Table 12.
Evaluation boards ordering information
Description USB2 VT5376 high-speed imaging system evaluation board VT5376 sensor in a full-speed wired laser mouse evaluation board VT5376 sensor in a low-speed wireless laser mouse evaluation board
Order code STV-376-E01 STV-376-E02 STV-376-E03
12
Revision history
Table 13.
Date 27-Sep-2007
Document revision history
Revision 1 Initial release. Updated - Chapter 1: Motion performance - Chapter 2: Power supply options and power consumption - Chapter 3: Electrical characteristics - Chapter 5: I2C control register map - Chapter 6: Laser - Chapter 7: General features - Chapter 8: Typical application - Chapter 9: Pinout - Chapter 10: Package mechanical data - Chapter 11: Ordering information - Image download sections (Section 7.4 and Section 7.5) Changes
09-Sep-2008
2
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VT5376
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