TSL2521 ALS/Flicker
TSL2521 ALS and Flicker Settings
Application Note
• PUBLIC
AN001042
• v1-01 • 2022-Jan-27
23
│ 4
2
TSL2521 ALS and Flicker Settings
2.1
ALS Channels/Modulators
The datasheets of ALS legacy devices used to name the measurement channels after their filters, e.g.
the Clear channel, Red channel, Blue Channel and so on. It was possible on devices like TCS3707 to
change the Diode-to-channel connection via a multiplexer, but this was not easy during measurements
and therefore not often used.
The TSL2521 has only two ALS channels but it is very easy to change the connection between the
individual diodes
– no matter which filter is on this diode – and the ALS engine. Consequently, channel
related registers are not named after the filter characteristic of the diodes
– like Clear (C) and Infrared
(IR)
– but after the two available ALS modulators: modulator 0 and modulator 1.
Figure 1 shows the number and filter type of the six available photodiodes on TSL2521. The
photodiode numbers are used to connect the photodiodes to the modulators in the SMUX registers
MEAS_SEQR_STEP0_MOD_PHDX_SMUX_L
up to
MEAS_SEQR_STEP3_MOD_PHDX_SMUX_H
.
The default setting has to be changed since it refers to a different filter layout: modulator 0 should be
connected to the four Clear diodes 1, 2, 3, and 4; modulator 1 should be connected to the two IR
diodes 0 and 5. There is no separate channel/modulator for the flicker measurements, every
modulator can be used for both 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)
