116 lines
2.7 KiB
C
116 lines
2.7 KiB
C
/*
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* - The input is fixed to 50 MHz
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* f_REF = 50 MHz
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*
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* - The VCO must operate between 3 GHz and 6 GHz
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* f_VCO range: 3 GHz - 6 GHz
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*
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* Phase Detector Clock:
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* - We configure the phase detector to not change the
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* input signal
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* f_PFD = f_REF x [(1 + DBR)/(R x (1 + RDIV2))]
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* R = 1
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* DBR = 0
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* RDIV2 = 0
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*
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* => f_PFD = 50 MHz
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*
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*
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* f_RFOUT < 3 GHz:
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* - To go to < 3 GHz, f_VCO has to be divided.
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* f_RFOUT = f_VCO / DIVA
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*
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* - We just divide by 2 for now
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* DIVA = 2
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* => f_RFOUT = f_VCO / 2
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*
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* - Relationship between f_PFD (fixed) and f_VCO (variable)
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* N + (F/M) = f_VCO/ f_PFD
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*
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* - Insert relationship between f_RFOUT and f_VCO:
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* N + (F/M) = (f_RFOUT * 2) / f_PFD
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* f_RFOUT = (N + F/M) * f_PFD / 2
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*
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* - Limits for N, M and F from the datasheet:
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* 19 <= N <= 4091
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* 2 <= M <= 4095
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* F < M
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*
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* - Plug in constants:
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* f_RFOUT = (N + F/M) / 2 * 50 MHz
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*
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* - Given the range of N, we can go to:
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* f_RFOUT range: 475 MHz - 3 GHz
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*
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* - N steps in 25 MHz increments:
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* N = floor(f_RFOUT / 50 MHz * 2)
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* => N = (f_RFOUT * 2) / 50 MHz (uses integer math)
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*
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* - Calculate the error:
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* f_int_ERROR = f_RFOUT - (N * 50 MHz) / 2
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* f_int_ERROR range: 0 MHz - 24 MHz
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*
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* - Use the fraction to get to the correct frequency:
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* (F/M) / 2 * 50 MHz = f_int_ERROR
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*
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* - Fix M:
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* M = 25
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*
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* - Calculate F:
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* (F/25) / 2 * 50 MHz = f_int_ERROR
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* F = f_int_ERROR / 1 MHz
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*
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* - Calculate the new error:
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*
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* f_ERROR = f_RFOUT - (N + F/M) / 2 * 50 MHz
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* f_ERROR range: 0 MHz - 1 MHz
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*
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*
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* f_RFOUT > 3 GHz:
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* - Do not divide the VCO output
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* DIVA = 1
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* => f_RFOUT = f_VCO
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*
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* - Relationship between f_PFD (fixed) and f_VCO (variable)
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* N + (F/M) = f_VCO/ f_PFD
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*
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* - Insert relationship between f_RFOUT and f_VCO:
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* N + (F/M) = f_RFOUT / f_PFD
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* f_RFOUT = (N + F/M) * f_PFD
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*
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* - Limits for N, M and F from the datasheet:
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* 19 <= N <= 4091
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* 2 <= M <= 4095
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* F < M
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*
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* - Plug in constants:
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* f_RFOUT = (N + F/M) * 50 MHz
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*
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* - Given the range of N and the VCO limits, we can go to:
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* f_RFOUT range: 3000 MHz - 6000 MHz
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*
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* - N steps in 50 MHz increments:
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* N = floor(f_RFOUT / 50 MHz)
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* => N = f_RFOUT / 50 MHz (uses integer math)
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*
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* - Calculate the error:
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* f_int_ERROR = f_RFOUT - N * 50 MHz
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* f_int_ERROR range: 0 MHz - 49 MHz
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*
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* - Use the fraction to get to the correct frequency:
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* (F/M) * 50 MHz = f_int_ERROR
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*
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* - Fix M:
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* M = 50
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*
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* - Calculate F:
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* (F/50) * 50 MHz = f_int_ERROR
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* F = f_int_ERROR / 1 MHz
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*
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* - Calculate the new error:
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*
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* f_ERROR = f_RFOUT - (N + F/M) * 50 MHz
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* f_ERROR range: 0 MHz - 1 MHz
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*
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*/
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