Jieli AD15n For Low Speed USB Device
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Introduction
I want to design the lowest cost USB NFC Reader&Writer, then I found Jieli AD15n(it's price is only ￥1.0,about $0.15):
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Background
Universal Serial Bus Specification Revision 1.1 7.1.11 Data Signaling Rate The low-speed data rate is nominally 1.50Mb/s. The permitted data-rate tolerance for low-speed functions is ±1.5% (15,000ppm).
AD15n's LSB default value is 80MHz, and it can be divided by n for LSB device(include IO&PWM).
NFC readers use NFC frequency of about 13.56 MHz, and 13.56/9/1.5-1=0.444% < 1.5%. If the LSB can be overclocked to 81.36MHz(13.56*6), it will work for NFC and USB low speed device.
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Test
Fortunately, I tuned the PLL of AD15n, it works.
https://gitee.com/MCUer/AD15N-App/blob/master/02-USB/COMM/USB_CLK.C