Tuesday, July 5, 2011
Silicon Labs Si4831 Chip and the Tecsun R-2010
Many of us are anticipating the arrival of the new Tecsun R-2010 DSP radio. This radio will use the Silicon Labs Si4831/35-B30 chip, developed for consumer AM/SW and FM operation. This second generation mechanically-tuned digital CMOS AM/FM/SW radio receiver IC integrates the complete receiver function from antenna input to audio output into one chip, like the Tecsun PL-380's Si4734 digital chip did. The difference: this chip is analog-tuned.
Band coverage of the new chip is 504 KHz to 1750 KHz in the mediumwave band, 5.6 MHz to 22.0 MHz in the shortwave band, and 64 MHz to 109 MHz in the FM band. Note that the 120, 90, and 60 meter tropical bands are not available. Also note that the longwave band is not supported.
AM sensitivity is comparable to the Si4734 chip, at 30µV input for 26dB (S+N)/N (signal plus noise to noise). The PL-380's Si4734 chip had a typical 25µV (S+N)/N sensitivity.
The receiver IC has very low power consumption and runs off of two AAA batteries. Typical supply current at 2.7 to 3.6 volts input is 17ma. Shutdown mode (power off) requires an insignificant 10µa.
The main external components required are a 100K ohm tuning pot, LED tuning and power indicators, a ferrite loopstick antenna for mediumwave reception and telescoping whip for shortwave and FM. Again, similar to the Si4734 chip, the antenna ferrite inductance required will be 180-450 µH. The Si4831 also supports an air loop antenna for AM. Air core loop support is suggested through an external 1:5 transformer, raising the input inductance 25 times, allowing for an actual air loop inductance between 10 and 20µH. The PL-380's Si4734 chip also supported the air core loop in the same way.
No mention of soft-muting or user-selectable bandwidth filtering is found in the currently available Si4831 documentation. Surely this chip would have the capability of multiple bandwidths. In the documentation they describe "....patented architecture allows for high-precision filtering, offering excellent selectivity and SNR with minimum variation across the AM band." Selection of bandwidths on the Tecsun PL-380's chip was done by program code. Let's hope this one has the ability.
Frequency drift tests show perfection compared to a traditionally capacitance-tuned radio like the Sony ICF-C218 clock radio. Hot and cold tests performed (room temperature to 45C and room temperature to -10C) resulted in virtually zero drift.
As an added bonus, use of a mechanical resistive tuning pot allows the frequency to be displayed in a linear format on the dial, so frequencies at the high end of the band are not crammed together as with capacitive tuning.
The size of this unit is unknown to me, although it looks similar in format to the Tecsun R-9012 or the Kaito WRX911. Both of these units are cigarette pack-sized.
Silicon Labs recently reached a major milestone in the broadcast audio market, announcing that it has shipped its one billionth broadcast radio IC. Silicon Labs’ digital CMOS broadcast radios are widely used in handsets, portable media players (PMPs), personal navigation devices (PNDs), automotive infotainment systems, tabletop and bedside radios, portable radios, boom boxes and numerous other consumer electronics products.
Silicon Labs introduced the industry’s first single-chip FM receiver in 2005, the Si4700 IC. As the industry’s smallest, highest performance and most integrated FM broadcast radio IC, the Si4700 redefined how FM tuners were designed into consumer electronics products.
I eagerly await the introduction of the Tecsun R-2010.