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REFERENCE CLOCK: application on Sysol ME and Dragon Fly

REFERENCE CLOCK: application on Sysol ME and Dragon Fly. VYn_ps12660 CS - Philips Semiconductors Le Mans. Introduction : Importance of the reference clock. Reference clock: Motor of the mobile All mobile functions depend on it

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REFERENCE CLOCK: application on Sysol ME and Dragon Fly

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  1. REFERENCE CLOCK: application on Sysol ME and Dragon Fly VYn_ps12660 CS - Philips Semiconductors Le Mans

  2. Introduction: Importance of the reference clock • Reference clock: Motor of the mobile • All mobile functions depend on it • Bad reference clock’s performances means bad mobile’s performances

  3. Training Content: • Reference clock presentation • Reference clock contents • Reference clock on Sysol ME • Reference clock working on Sysol ME • Reference clock performances to check • Problems linked to reference clock • Reference clock on Dragon Fly

  4. Training Content: • Reference clock presentation • Reference clock contents • Reference clock on Sysol ME • Reference clock working on Sysol ME • Reference clock performances to check • Problems linked to reference clock • Reference clock on Dragon Fly

  5. REFERENCE CLOCK PRESENTATION

  6.  Heart of the mobile:

  7. For Base-Band: - Clock for processor - Generation of all clocks

  8. For the Radio part: Reference clock for the synthetisers (PLL) With Fout= N x Fref

  9. In Sysol 2

  10.  Frequency of the reference clock • Fref = N x 13 MHz • For ALL GSM mobiles • 13000 kHz/48 = 270.833 kbits/s 48 clock cycle = 1 time bit 12 clock cycle = 1 quarter bit (time unity in mobiles) System clock must allow to have complete quarter bits. It is this with 3.25, 6.5, 13, 26 MHz

  11. Training Content: • Reference clock presentation • Reference clock contents • Discrete or integrated • Reference clock on Sysol ME • Reference clock working on Sysol ME • Reference clock performances to check • Problems linked to reference clock • Reference clock on Dragon Fly

  12. REFERENCE CLOCK CONTENTS

  13. Reference clock purpose: • Provide a sinusoidal signal with a stable frequency of Nx13 MHz: No square waves generator  32 kHz of BB is not enough - Not enough stable - Can’t provide easily Nx13 MHz

  14. Use of a Crystal-based oscillator

  15. Description of a quartz • The piezo electrical quartz crystal is deformed by the application of an electrical voltage. The crystal behaves like an electrical resonance circuit .  • Z: Quartz impedance with no load

  16. Oscillation conditions • The quartz is not perfect. It has losses  Oscillations can not appear • Losses must be compensated • « Negative resistor » (amplifier) needed

  17. Let’s see electrical characteristics of a crystal

  18. Crystal has others defaults: • Tolerance on components value  Frequency initial adjustment: RefCal Done on the production line • Frequency shift vs. temperature  Temperature compensation • Frequency shift with age  Frequency adjustment: AFC

  19. Crystal temperature deviation 416 Hz deviation 520 Hz deviation 156 Hz deviation

  20. Influence of V supply (Pushing)  Regulated supply • Influence of load (Pulling)  Load adjustment + Buffers + Frequency drift with time  Frequency enslavement: AFC

  21. Final overview of the clock Output BB AFC Output RF RefCal

  22. Discrete vs integrated clock • Two ways to implement the clock: • Discrete. Each function is done with discrete components • Module. Reference clock is generated by a component containing all functions

  23. Advantages Nber of components Reduced bulkiness Nber of supply Nber of signals Easy to implement Disadvantages Cost (twice discrete’s) No possible adaptation Module clock

  24. Disadvantages Nber of components Bulkiness Nber of supply Nber of signals difficult to implement Technical limits Advantages Cost (half module) Possible adaptation Discrete clock

  25. Discrete clock is limited to GPRS class 10, 2 Tx slots (due to PA heat) • Synchronisation algorithm is common • Temperature compensation:  hardware way for discrete  Integrated in the module • Temperature and load compensation are made internally for the module: RefCal not needed. • Consumption is a little bit important for module (~ 1 mA).

  26. Overview of a module clock No RefCal

  27. Training Content: • Reference clock presentation • Reference clock contents • Reference clock on Sysol ME • Reference clock working on Sysol ME • Reference clock performances to check • Problems linked to reference clock • Reference clock on Dragon Fly

  28. REFERENCE CLOCK ON SYSOL ME

  29. Topology of the 26MHz • The topology of the 26MHz oscillator is from Pierce principle as follows. 3537

  30. Characteristics of the ref. clock on SSME • Frequency: 26 MHz  Radio: UAA3537. Need 26 MHz  BBand: OM6357-7 (50874-6): 26 MHz • Quartz: NDK NX4025DA 26 MHz • Semi-integrated clock: Three blocks are in 3537: - RF buffer - BB buffer - Negative resistance

  31. Supply for the clock: not needed. Negative resistance and buffers supplies are provided by 3537 with an internal regulator. • Signals: 2 signals are needed:  AFC: provided by BB  Clkfdbx: provided by 3537 • RefCal signal is generated by a register of 3537. (CAFC register)

  32. Crystal NX4025DA specifications

  33. Internal regulator Clkfdbk from 3537 Temperature compensation Negative resistance AFC: from BB RF Buffer VariableLoading Quartz BB Buffer

  34. Training Content: • Reference clock presentation • Reference clock contents • Reference clock on Sysol ME • Reference clock working on Sysol ME • Reference clock performances to check • Problems linked to reference clock • Reference clock on Dragon Fly

  35. REFERENCE CLOCK WORKING ON SYSOL ME

  36. Some hard parameters • Magnitude of the clock:  Input of 3537: 670 mVpp  Provided by 3537: 1.2 Vpp • DC value: 1.2 V 3537 specifications.

  37. Input of 3537 F=26 MHz (Refin pin) Output of 3537 F=26MHz

  38. Synchronisation with network • Step 1: wake up of the 26 MHz  26 MHz is not the real frequency.  Clock is not enslaved • Step 2: Mobiles goes in Rx mode to receive the FCB DESPITE the clock is not at 26 MHz (FCB: Frequency Control Burst) • Step 3: with FCB, mobile can correct its frequency error.

  39. After synchronisation with network • Regularly, mobile measures the frequency error with FCB  Frequency Offset Information (FOI) • Software value, given by tracer or a communication tester (CMD) • Coded with 16 bits (2 bytes). • Positive FOI value = negative frequency error. • Negative FOI value = positive frequency error. • Using FOI information, mobile adjusts AFC.

  40. How mobile adjusts AFC: FOI_STEP • Using FOI information, mobile increases or decreases AFC. • Since AFC is provided by AuxDAC2 on 50732, it can change only step by step. Foi_step

  41. FOI_STEP Calculation • Take the specified minimum voltage range of the AFC DAC defined by ΔV ( unit in V). • The correction per LSB is derived by: ΔV/(2n) for a n bits DAC (unit in V). • Then, the TCXO slope needs to be measured on a statistical quantity of units (> 30). The slope is expressed by S (unit in ppm/V).

  42. FOI_STEPphy is equal to (ΔV x S x F)/ 2n(unit in Hz/LSB) Where F is the middle Rx RF frequency corresponding to the band used for the calculation881.4 x 106 Hz for the GSM850 (channel 189). 942.4 x 106 Hz for the GSM900 (channel 62). 1842.6 x 106 Hz for the GSM1800 (channel 699). 1960 x 106 Hz for the GSM1900 (channel 661). • The correction is: (FOI/ FOI_STEPphy) (unit in LSB)

  43. BUT: a division between an integer and a real number is an inconvenient operation for soft Parameter FOI_step FOI_STEP = 216/(FOI_STEPphy)(unit LSB/Hz) • Thus, we have: [216/(FOI_STEPphy)] x [FOI / 216]=[FOI_STEP] x [FOI / 216] Instead of:FOI / FOI_STEPphy One multiplication better than a division One division with an integer One division between one integer and one real number

  44. What will happen if initial frequency error is too important? Mobile can not synchronize Use of an Initial FOI (FOInit)

  45. DSP has a Rx frequency window (+/- 25 kHz). It comes from DSP firmware. • Mobile can synchronize only if frequency error is in this window • FOI_Init put frequency error in the synchronization range

  46. Settings of this parameters • REF_Cal, FOI_Init, FOI_Step are stored in EEPROM • It is possible to see and change their value with TAT software • Ref_Cal and FOI_Init are tuned for each mobile. • Ref_Cal is first tuned, then Foi_Init. • FOI is a soft parameter. Value accessible only with TRACER or Communication TESTER

  47. FoiStep: One per band Foi-Init: Needs an HWL reset (init button) RefCal

  48. Values for Sysol ME (updated on W347) • FOIinit: 2340 * • RefCal: 78 ** • FOIstep GSM850: 8082 • FOIstep GSM900: 7759 • FOIstep GSM1800: 3856 • FOIstep GSM1900: 3634 * : Depends on layout, quartz, diode… ** : Statistical value * & **: Defaults values – Tuned in production

  49. GSM standard requirements: • In all bands, in normal conditions, frequency error must not be greater than 0.1 ppm • For GSM 850: 85 Hz • For GSM 900: 90 Hz • For DCS 1800: 180 Hz • For PCS 1900: 190 Hz

  50. Training Content: • Reference clock presentation • Reference clock contents • Reference clock on Sysol ME • Reference clock working on Sysol ME • Reference clock performances to check • Problems linked to reference clock • Reference clock on Dragon Fly

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