introduction
Bluetooth (Bluetooth technology) is a short-range wireless communication protocol standard initiated by information technology companies such as Ericsson, Nokia, Motorola, Intel, IBM and Hitachi. Because Bluetooth technology has low power consumption, strong anti-interference ability, suitable for a variety of communication sites and relatively simple integrated circuits, Bluetooth technology has a broad market prospect as a wireless interface technology that replaces wired cables. Bluetooth technology is becoming the standard configuration in mobile phones, PDAs, MP3players and computers. One of the mainstream applications of Bluetooth technology is to enjoy the high-quality music sent by the Bluetooth interface of the above products through Bluetooth headsets and to achieve hands-free calling. It is not only related to the advancement of the technology itself, but also closely related to the level of implementation costs. The price of Bluetooth headsets on the market ranges from a few hundred to more than a thousand yuan, and the price of mobile phones themselves is mostly not more than a thousand yuan. The relatively high price has caused its market penetration speed and breadth to be much lower than that of mobile phones. This article is based on these. Based on the CSR Bluetooth chip BC358239A, a low-cost Bluetooth headset circuit design scheme is proposed, which will play a role in the popularity of Bluetooth headsets Important role.
One. Bluetooth headset architecture and chip introduction
Figure 1 Structure of Bluetooth headset
In addition to low cost, low power consumption, and simple peripheral circuits, the chips used in Bluetooth headsets are also important to provide complete software development tools and small chip packages. The following is a brief introduction to the main chips of Bluetooth headsets.
1. BC358239A introduction:
BC358239A chip frequency range 2.402 ～ 2.480Ghz, transmit power can be up to + 4dB, built-in 8-bit DAC (digital-to-analog converter) can automatically adjust the transmit power, without external BALUN (balanced unbalanced converter and power amplifier can comply with Bluetooth V1.2 Specification; typical receiving sensitivity at 0.1% BER (bit error rate)-85dB; fully integrated frequency synthesizer, which can support 8 ~ 40Mhz external clock input and external CRISTAL (crystal oscillator); internal integrated DSP (digital signal processor) Speed ​​up to 32MIPS, 32bit instruction word, 24bit data memory, built-in 4K word program memory, two 8K word data memory, enough to support headset application software design needs; on-chip LDO (low dropout linear regulator), support u-law and A-law voice code conversion, support I2S and PCM voice interface, deep sleep mode power consumption does not exceed 10uA; 10x10mm LFBGA package requires only a small PCB size. BC358239A internal structure shown in Figure 2.
Figure 2 BC358239A internal structure
In addition, BC358239A has a built-in LDO, its output voltage is 1.8V, and its maximum output current can reach 70mA, which can fully meet the needs of the Bluetooth chip itself.
BC358239A's Bluetooth software architecture has considerable flexibility. Bluetooth applications can run outside BC358239A or be handled by the internal RISC processor.
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