MLX75031 Datasheet, PDF (23/67 Pages) Melexis Microelectronic Systems – Optical Gesture & Proximity Sensing IC

MLX75031
Optical Gesture & Proximity Sensing IC
with Integrated LED Drivers
Datasheet
Piece Wise Linear DAC voltage vs DAC codes
1.2
1
0.8
0.6
0.4
0.2
0
0
50
100
150
200
250
300
DAC codes (LSB)
Figure 5 : Piece Wise Linear DAC voltage vs DAC codes
8.5.2. LED Driver
The LED driver mainly contains one operational amplifier and transistors able to drive the external LEDs.
Its task is to set the voltage over the external Rshunt equal to the voltage generated by DAC, so the
corresponded current (Vdac/ Rshunt) is flowing through LED.
The error flag Err_Drv is set high if the LED current regulation loop is broken (disconnected LED or shunt
resistor).
8.5.3. LED Forward Voltage Measurement
When the current pulse is flowing through the LED, the voltage drop across the LED (between pin
Drive_LEDA/B and pin ShuntR) is sampled and then held for later ADC conversion.
This value can be used to estimate the LED temperature.
The sampling occurs synchronously with the Active Light signal sampling.
REVISION 001 – JANUARY, 2013
39010xxxxx
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