VCNL4200

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Vishay Semiconductors

Rev. 1.6, 20-Jul-2022

13

Document Number: 84430

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Threshold Window Setting

• ALS Threshold Window Setting (Applying ALS INT)

Register: ALS_THDH_L and ALS_THDH_H define 16-bit ALS high threshold data for LSB byte and MSB byte. Register:

ALS_THDL_L and ALS_THDL_H define 16-bit ALS low threshold data for LSB byte and MSB byte. As long as ALS INT function

is enabled, INT will be asserted once the ALS data exceeds ALS_THDH or goes below ALS_THDL. To easily define the

threshold range, multiply the value of the resolution (lx/step) by the threshold level (refer table 14)

•ALS Persistence

The ALS INT is asserted as long as the ALS value is higher or lower than the threshold window when ALS_PERS

(1 / 2 / 4 / 8 times) is set to one time. If ALS_PERS is set to four times, then the ALS INT will not be asserted if the

ALS value is not over (or lower) than the threshold window for four continued refresh times (integration time)

• Programmable PS Threshold

VCNL4200 provides both high and low thresholds 8-bit data setting for proximity sensor. (register: PS_THDL, PS_THDH) that

fulfills different mechanical designs with the best proximity detection capability for any kind of objects

•PS Persistence

The PS persistence function (PS_PERS 1 / 2 / 3 / 4) helps to avoid false trigger of the PS INT. For example, if

PS_PERS = 3 times, the PS INT will not be asserted unless the PS value is greater than the PS threshold (PS1_THDH)

value for three periods of time continuously

Data Access

All VCNL4200 command registers are readable. To access 16-bit high resolution ALS output data, it is suitable to use read word

protocol to read out data by just one command at register: ALS_Data_L and ALS_Data_H. To represent the 16-bit data of ALS,

it has to apply two bytes. One byte is for LSB, and the other byte is for MSB as shown in table 18. In terms of reading out 8-bit

PS data, host just need to access register: PS_Data.

Interrupt (INT)

VCNL4200 has ALS and PS interrupt feature operated by a single pin “INT”. The purpose of the interrupt feature is to actively

inform the host once INT has been asserted. With the interrupt function applied, the host does not need to constantly poll data

from the sensor, but to only read data from the sensor when receiving interrupt request from the sensor. As long as the host

enables ALS interrupt (register: ALS_INT_EN) or PS interrupt (register: PS_INT) function, the level of INT pin (pin 8) is able to be

pulled low once INT asserted. All of registers are accessible even INT is asserted.

ALS INT asserted when ALS value crosses over the value set by register: ALS_THDH or is lower than the value set by

register: ALS_THDL.

PS INT asserted when PS value crosses over the value set by register: PS_THDH or is lower than the value set by

register: PS_THDL.

Interrupt Flag

Register: INT_Flag represents all of interrupt trigger status for ALS and PS. Any flag value changes from “0” to “1” state, the

level of INT pin will be pulled low. As long as host reads INT_Flag data, the bit will change from “1” state to “0” state after reading

out. The INT level will be returned to high afterwards.

TABLE 14 - ALS RESOLUTION AND MAXIMUM DETECTION RANGE

ALS_IT

SENSITIVITY

(lx/step)

MAXIMUM DETECTION

RANGE

(lx)

ALS_IT

(7 : 6)

INTEGRATION TIME

(0, 0)

50 ms

0.024

1573

(0, 1)

100 ms

0.012

786

(1, 0)

200 ms

0.006

393

(1, 1)

400 ms

0.003

197

TABLE 15 - 16-BIT ALS DATA FORMAT

VCNL4200

Bit

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Register

ALS_Data_H

ALS_Data_L