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Osram ams TSL2521 Manual

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Summary of Contents for Osram ams TSL2521

  • Page 1 Product Document Published by ams OSRAM Group...
  • Page 2 Application Note AN001042 TSL2521 ALS/Flicker Settings and Comparison to Legacy ALS Devices v1-01 • 2022-Jan-27...

  • Page 3: Table Of Contents

    Document Feedback TSL2521 ALS/Flicker Content Guide Content Guide 24-Bit ALS Result Data Transferred Via Introduction ........3 FIFO ............16 TSL2521 ALS and Flicker Saturation and Maximum Value of ALS Settings .......... 4 Result ............16 Flicker Result Data Format ..19 ALS Channels/Modulators ......

  • Page 4: Introduction

    Document Feedback TSL2521 ALS/Flicker Introduction Introduction TSL2521 offers new ALS and Flicker measurement features on a very small space of 2.0 mm x 1.0 mm x 0.5 mm compared to legacy devices. ALS and flicker are running on the same time base, the FIFO is larger, it has some data compression features, and measurements can be planned in sequences with individual settings.

  • Page 5: Tsl2521 Als And Flicker Settings

    ALS and Flicker measurements at the same time. On TSL2521 flicker measurements should be done preferred on modulator 0 with the Clear diodes. The GUI and the drivers provided by ams OSRAM have both mentioned changes implemented. Figure 1: Location, Filter Type, and Number of Photodiodes of TSL2521 (top view) Application Note •...

  • Page 6: Sequencer

    Document Feedback TSL2521 ALS/Flicker TSL2521 ALS and Flicker Settings Information In application cases with high transmissivity glass direct sunlight could cause saturation even at gain setting of 0.5x especially on modulator 0 connected to the Clear diodes. This can be avoided by connecting less than 4 of the Clear diodes to modulator 0 in the SMUX registers of the sequencer.
  • Page 7 Document Feedback TSL2521 ALS/Flicker TSL2521 ALS and Flicker Settings Since the Residual measurement is done with a resolution of max. 4 bits on this device that results in 4 extra resolution bits almost for free. That way it is possible to use lower gains that have a better linearity than higher gains, because the Residual bits provide additional resolution on LSB side.
  • Page 8 The GUI provided by ams OSRAM can show both methods, Figure 4 with the “Integer view box” checked shows the internal integer view with 4-bit Residuals on LSB side like in Figure 5.
  • Page 9 It is recommended to place ALS measurement and Flicker measurement into separate steps of the sequencer in order to avoid noticeable influence of Residual measurement time onto the ALS integration time. This is what the GUI and the drivers provided by ams OSRAM do as well. Application Note • PUBLIC AN001042 •...

  • Page 10: Als And Flicker Timing

    Document Feedback TSL2521 ALS/Flicker TSL2521 ALS and Flicker Settings ALS and Flicker Timing For ALS measurements one of the most important parameters is the ALS integration time. On legacy devices like the TCS3707 that was the product of the modulator clock period at e.g. 2.78 µs, the value in the ASTEP register (+1) and the value in the ATIME register (+1) as shown in Equation 3.
  • Page 11 Document Feedback TSL2521 ALS/Flicker TSL2521 ALS and Flicker Settings Figure 8: Step 0 of TSL2521 Sequencer with ALS and Flicker Measurement Activated ALS Result ALS integration time Pause Flicker measurement time sample time FIFO used for Ficker data Figure 9: Example Specification and Proposed Settings Item Value [dec.]...

  • Page 12: Als/Flicker Gain And Agc

    Document Feedback TSL2521 ALS/Flicker TSL2521 ALS and Flicker Settings ALS/Flicker Gain and AGC Another fundamental parameter for ALS measurement is the ALS gain setting. For ALS legacy devices like TCS3707 there was a single AGAIN value. For TSL2521, the gain is set per modulator and even for every sequence individually.

  • Page 13: Wait Time

    Document Feedback TSL2521 ALS/Flicker TSL2521 ALS and Flicker Settings mod_calib_nth_iteration_agc_enable in register MOD_CALIB_CFG2. Please note that this bit is not enabled by default but has to be enabled to use one or both of the AGC methods. Information The same mode_calib_nth_iteration setting is used for the Autozero as well. Since the ALS Autozero procedure can take a longer time it might be necessary to disable the bit mod_calib_nth_iteration_az_enable in register MOD_CALIB_CFG2 after the first measurement.

  • Page 14: Als Result Data Format

    Document Feedback TSL2521 ALS/Flicker ALS Result Data Format ALS Result Data Format Internal Data Format Internally the ALS result is stored in a 32-bit word. The 4 LSB bits are always reserved for residual counts, no matter if they are measured or not – if not, they are set to 0. If there are less Residuals bits chosen or measured than 4 there are still 4 bits reserved in the ALS result format - the ones on the LSB side that are not measured are set to 0.

  • Page 15: 16-Bit Data Full Count Results In Als_Data

    Document Feedback TSL2521 ALS/Flicker ALS Result Data Format Information Setting als_msb_position to the right format is necessary to get a valid als_digital_saturation bit. 16-Bit Data Full Count Results in ALS_DATA Registers In case the ALS results should be read over the ALS_STATUS and ALS_DATAx registers the 16-bit full counts can be read out like in legacy devices without using the FIFO –...
  • Page 16 Document Feedback TSL2521 ALS/Flicker ALS Result Data Format as shown in Figure 12. The host takes the 16-bit number, checks the als_datax_scaled register and – because it is 1 - just adds 4 bits 0 on MSB side to get a 20-bit number. Figure 12: Scaled Data Transfer of ALS Data Including Residual Counts 20 bit...

  • Page 17: 24-Bit Als Result Data Transferred Via Fifo

    Document Feedback TSL2521 ALS/Flicker ALS Result Data Format Using this kind of ALS result format gives both the dynamic range of the ALS legacy devices and the advantage of the residual measurement in lower light situations while keeping the 16-bit register width. Additionally, it is possible to use this both with Residual measurement enabled or disabled, the number space is consistent in this case.
  • Page 18 Document Feedback TSL2521 ALS/Flicker ALS Result Data Format 3.5.1 Analog Saturation Analog saturation means that the signal from the photodiodes amplified by the gain stage is that high that it cannot be checked fast enough by the modulator circuit. It is signaled by the bits als_datax_analog_saturation_status dedicated for each modulator in register ALS_STATUS, the result set of all modulators needs to be ignored in this case.
  • Page 19 Document Feedback TSL2521 ALS/Flicker ALS Result Data Format Equation 8: ������_������_����������_������ℎ_������������������ ≥ ((������_����_�������������� + 1) ∗ (������������_�������� + 1) − 22) ∗ 16 Application Note • PUBLIC AN001042 • v1-01 • 2022-Jan-27 │ 18...

  • Page 20: Flicker Result Data Format

    Document Feedback TSL2521 ALS/Flicker Flicker Result Data Format Flicker Result Data Format Internal Flicker Data Format Flicker data is at maximum 15 bits large as shown in Figure 14 – again 4-bit Residuals on LSB side and maximum 11-bit for full counts since the field sample_time is 11-bit wide. Internally these maximum 15 bits are stored in a 16-bit data register.

  • Page 21: Flicker Data Transfer Via Fifo

    TSL2521 has a built in non-destructive flicker data compression mode as well that reduces the I traffic significantly, the drivers provided by ams OSRAM show and document the use of these features.
  • Page 22 Document Feedback TSL2521 ALS/Flicker Flicker Result Data Format Figure 17: FIFO Structure Example for Flicker Measurement Enabled on One Modulator With Flicker Gain Written and 4 Flicker Samples Measured (fd_nr_samples = 3) In case of reduced Flicker bit width the last FIFO byte containing flicker data gets filled up to full 8-bit on MSB side with 0 before the gain data is pushed to the FIFO.

  • Page 23: Revision Information

    Document Feedback TSL2521 ALS/Flicker Revision Information Revision Information Changes from previous version to current revision v1-01 Page Initial version Corrected number of preferred modulator for flicker measurements ● Page and figure numbers for the previous version may differ from page and figure numbers in the current revision. ●...

  • Page 24: Legal Information

    No obligation or liability to recipient or any third party shall arise or flow out of ams-OSRAM AG rendering of technical or other services.

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