AN555 View Datasheet(PDF) - Silicon Laboratories
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AN555 Datasheet PDF : 38 Pages
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AN555
Figure 11. Si483x-B/Si4820/24 Default Volume Selection in Volume Mode
3.5. Application Circuits for Memorization of User Settings
Si483x-B/Si4820/24 has high retention memory (HRM) built-in that can memorize the last volume and bass/treble
settings so that at the next power up, the unit will automatically restore the volume and bass/treble settings before
the last power off. The unit requires pin 20 Vdd1 to be connected to an always-on power source such as battery
terminals.
During power off/on cycling, there is a low probability that the user setting data in HRM can be corrupted by
transient. If the tuner finds that the stored data in HRM is corrupted at power on, it will switch to use the default
volume or bass/treble setting. To safeguard the integrity of HRM data, users are advised to ensure that the Reset
pin (RSTB) voltage goes down to 0.3*VDD before the VDD2 voltage drops to 1.65 V during the power off process.
A 2P2T, power on/off switch S3 in Figure 12 is recommended, with one pole of S3 short pin15 RSTB to GND
immediately at the power off event.
Applying always-on power supply voltage to Vdd1 and using 2P2T power on/off switch to connect RSTB will also
improve the tuned channel consistency before power off and after power on. Si483x-B/Si4820/24 memorizes the
last tuned station before power off and restores the original tuned station at power up after confirming that there is
not a large enough position change on PVR during the power off/on cycle.
Rev. 0.2
17
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