LP5520TL NSC [National Semiconductor], LP5520TL Datasheet - Page 18

• Manufacturer Part Number: LP5520TL
• Description: RGB Backlight LED Driver
• Manufacturer: NSC [National Semiconductor]

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Temperature and Light Measurement
LP5520 has a 12-bit Analog-to-Digital Converter for the mea-
surements. The ADC has two inputs. S1_IN input is intended
for the LM20 temperature sensor and S2_IN input for light
measurement or any DC voltage measurement. The conver-
sion results are filtered with average filter for 134 ms. The
<adc_ch> bit in the Control register selects, which conver-
sion result can be read out from the registers ADC_hi_byte
and ADC_low_byte. The ADC_hi_byte has to be read first.
comp_sel(bit4)
adc_ch(bit5)
0
1
0
1
S1 input can be read
S2 input can be read
S1 input is used for compensation
S2 input is used for compensation
18
The <comp_ch> bit selects, which input is used for compen-
sation. The ADC uses the LDO voltage 2.8V as the reference
voltage. The input signal range is 0 – 2.8V and the inputs are
buffered on the chip.
If S2_IN is used for light measurement using TDK optical
sensor BCS2015G1 as shown in the Block Diagram on page
5, the measurement range is from 10 to 20.000 lux when using
100k resistor.
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