Passive RFID chip H4006 and its application design
1 H4006 chip introduction
The H4006 has a operating frequency range of 10 to 15 MHz, usually 13.56MHz for identification. There is a 64-bit programmable memory in the film that can be used to store related information. The H4006 information transmission mode is loaded, encoded as the Miller, the data transfer rate is 26484 baud (may also be other rates, but need to be pre-selected). Because the H4006 contains resonant circuits and power filter capacitors, it is more convenient to use. H4006 is a read-only storage card in wireless mode, which is programmed in line programming.
2 Working principle
2.1 internal circuit block diagram
The H4006 is composed of a resonant circuit, a clock extraction, a frequency division chain, a rectifier circuit, a power management, a memory, a MILLER code, and a load modulation circuit, and the like, and the circuit block diagram is shown in Figure 1.
When the rectifier circuit rectifies the coupled radio frequency (13.56 MHz) and the filter capacitor C2 is smooth, the power supply management circuit will activate the card inner circuit when the power supply voltage reaches internal circuitry, and 13.56MHz signal is divided by the divided circuit. (The division coefficient is 512), a clock of 26.484 kHz can be generated. This clock is the baud rate of data transfer. If you want to specify the division of the division as 128, 256, 1024, 2048, 4096 or 8192, you need to be pre-selected. Information (64 bits) stored in LaserROM After reading, the MILLER code can be generated via the MILLER code generator, and the MILLER code can be used for load modulation and the storage information is sent out.
2.2 Inspiration parameter settings
Inductance L1 is the unique external element on the card, since the resonant capacitor C1 is integrated into the film, therefore, the inductance value of L1 at 13.56 MHz should be 1.4μH. To ensure the effect of carrier transmission and load modulation, its Q value is selected between 30 and 40.
2.3 Output sequence
The output of the card information is typically repeated in the sequence listed in Table 1. The output sequence is a 82-bit standard information structure (STDMS) plus 9-bit voids (PAUSE). The STDMS structural bits use a Miller code, while the 9-bit voids do not use a unrel code. At the gap bit, the load modulator switch is in turn-off state (OFF), and the gap bit level is low.
In Table 1, the composition of 64-bit data is as follows:
1 to 5 are combined with a wafer number, each wafer has a number, which can be set between 1 to 25. 6 ~ 9 is the manufacturer reserved position. 10 ~ 19 is the IC name, a total of 10 digits. 20 ~ 32 bits are the user ID (ID) bit, a total of 13 bits, which can be defined by the manufacturer. 33 ~ 50 is expanded, a total of 18 bits, this is the only system number. 51 ~ 64 Bits are set to the IC position number, a total of 14 bits, can be used to indicate the precise position of the machined wafer.
The polynomial generated by the CRC code in Table 1 is X16 + X12 + X5 + 1, which conforms to the CCITT / ISO3309-1984 standard. The CRC code is generated by 64-bit data and can be implemented with shift registers. This register is complex in each stop bit.
In addition, the starting position in the output sequence is usually logical 1, and the stop bit is logic 0.
2.4 Miller Code
In the data transfer, the advantage of Miller code modulation is that there is clock information in the MILLER code and has good anti-interference capabilities.
The coding method of the Miller code is shown in Table 2, and its waveform timing is shown in FIG.
Although the coding rule of the Miller code is a stop bit to logic 0, its level is different from its previous STMDS bit coding level. The level can be pulled low by using a 9-bit void (PAUSE) to enable the starting position in the same form. Figure 3 makes a clear description of this.
3 application design
Figure 4 shows the application system block diagram of the H4006. The system consists of two parts: card and card readers. Since the H4006 is a storage card, data transfer only from the card conversion card reader, there is no encoding and modulation circuit in the reader, only demodulation and decoding circuitry.
H4006 has 6 pins. When the radio frequency is operated, it is read-only, and the inductance L1 is connected to the C1 and C2 lead terminals, when the data is transmitted, the waveform on the card and the card reader antenna coil is shown in the figure, and the waveform is generated by the load modulation in the card. . The other four pins of the H4006 are used for testing, VDD and VSS are positive and negative terminals of the power, Testn and TOUT are test inputs and output.
Figure 5 shows a 13.56 MHz oscillator and a power amplifier circuit in the card reader. In the figure, the power amplifier circuit uses a high efficiency of the glutamic (E class) amplifier, so the impedance of the L1 blocking ring should be large enough, and should make the ICC flowing through its constant value, C5 is used to improve the performance of the amplifier, it can Eliminating the effect of transistor itself output capacitance. When the transistor is in a switching state, the entire amplifier is extremely efficient. The resonance frequency of the series resonance circuit composed of L3 and C9, C11, and C10 in the figure is 13.56 MHz, which should have a higher Q value to ensure that the output carrier is a sine wave. In fact, the L3 is still a coupling coil of the card reader, which produced carrier electromagnetic fields should comply with the requirements of non-contact IC card technology standards. L2, C8 is used to block high-end harmonics.
13.56 MHz oscillating signal generated by the crystal oscillator, all the way to the CPU clock in the card, and the other can be used to drive the penta amplifier after amplification.
Data can be obtained from the load modulation signal on L3 from C7 to the demodulation and decoding circuit. The demodulation can use the envelope detection method to restore the Miller code obtained by the demodulation to the microcontroller to send to the microcontroller from the serial port to the PC. Technology area
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