Practical application of digital tuning integrated circuit T2104 in radio

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The TA2104 is a monolithic digital tuning integrated circuit manufactured by Toshiba Corporation of Japan, which is dedicated to portable radios and earphone circuits. The launch time of TA2104 is not short, but because of its excellent performance, it is still widely used in the mainstream models of the current market. The TA2104 is applied to the new DE1121 radio introduced in the previous issue of Electronic World. This article describes the features and applications of this chip, as well as its connection in the actual radio (DE1121) circuit.

The TA2104 has two different shapes, one is a dual in-line structure, which is the SDIP24 package, and its model is TA2104BN. The other is a flat structure in the SSOP24 package, which is model TA2104BNF (Figure 1).

The TA2104BN and TA2104BNF contain AM/FM local oscillator, buffer, AGC, frequency discrimination and squelch circuits. Operating voltage range is wide 1.8V ~ 7V, working current is small, when the working voltage is 3V, FM (FM) operating current is 11mA, amplitude modulation (AM) is only 7mA, so low power consumption, low heat, especially suitable for Low-voltage pocket model. Because TA2104BN and TA2104BNF have the advantages of simple peripheral circuit, convenient use and stable and reliable performance, they are widely used in various brands of radios.

Both the TA2104BN and the TA2104BNF use a 24-pin structure. They not only have the same internal circuits, but the functions of the corresponding pins are exactly the same. The function of each pin is shown in Table 1. The difference between the two is that the maximum dissipated power PD is different, the TA2104BN is 1.2W, and the TA2104BNF is only 0.5W.

The internal circuit block diagram of TA2104BN and TA2104BNF is shown in Figure 2.

Figure 3 is an example of the TA2104BN and TA2104BNF application circuits recommended by the manufacturer. Let's take a look at the difference between the actual application and the example of the TA2104BNF in the Degen DE1121 radio. Compare the digital tuning circuit of Figure 3 with the DE1121 machine. It will be found that there are still some differences between the two. The bandpass filter (BPF) is not connected to the 2nd pin of the FM input of the 1DE1211. This bandpass filter (BPF) only allows the radio FM to receive the range frequency (88~). The signal of 108MHz passes, filtering out the signals of the remaining frequencies, so the elimination of BPF may affect the selection performance and signal-to-noise ratio (S/N) of the FM band. The 10th foot of the 2DE1121 machine does not use the 10.7MHz crystal oscillator, but uses the 10.7MHz FM IF transformer, which may also be cost considerations.

It is worth mentioning that the TA2104 can be directly replaced with the cheaper domestic digital tuning integrated circuit chip SP2104. SP2104 also has SP2104N and SP2104FN. The former corresponds to TA2104BN, and the latter is exactly the same as TA2104BNF.

SP2104 is produced by Wuxi Silicon Power Microelectronics Technology Co., Ltd., which is a manufacturer with large-scale integrated circuit R&D and production capacity. It covers power management, audio, communication, automotive electronics, motor control, power billing, etc. Aspect application.

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