STV-376-E01 STMICROELECTRONICS [STMicroelectronics], STV-376-E01 Datasheet - Page 17

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

VT5376
6
6.1
Figure 9.
Laser system driven by internal DAC
LASER_OUT
LASER_NEN
VT5376
laser_selected = 1
RBIN
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.
Application schematics using Laser or LED (driven with internal DAC or external
current source)
laser
VTOP
LED system driven by internal DAC
laser_selected = 0
led_dac_driven = 1
LASER_OUT
LASER_NEN
VT5376
RBIN
LED
VTOP
LED system driven by external drive
36X trk_led (active high)
laser_select = 0
led_dac_driven = 0
LASER_OUT
LASER_NEN
VT5376
RBIN
LED
VTOP
Laser
17/30