1. DIGITAL PHASE LOCKED LOOP
E E-524 DIGITAL VLSI LABORATORY
SAM VIVIN RAJ KRISHAN
HIMAKAR REDDY GADDAM
NARENDRA NAIDU LINGUTLA
December 12 , 2014

2. OUTLINE
 Introduction
 Specifications
 Design
 Schematics of Major Blocks
 Test Benches of Major Blocks
 Schematic and Test Bench of DPLL
 Challenges

3. INTRODUCTION
Digital Phase Locked Loop:
 Multiply Clock Frequency
 Clock Synchronization
 Less stable than DLL(2nd order)
Applications:
 Telecommunications
 Clock synchronization and multiplication in Micro processors
 Clock generation

4. SPECIFICATIONS
Name Value
Process SS, TT, FF
Supply 1.6V -1.98V
Temperature -40 C – 127 C
Input frequency 100 MHz
Output Frequency 1 GHz, 900MHz , 800MHz
Load 10 pF
SPECIFICATIONS

5. BLOCK DIAGRAM OF PHASE LOCKED LOOP
PHASE
DETECTOR
LOOP
FILTER
DIVIDE BY 10
Fout
Feedback
Signal(Fout/N)
Finput
PUSH
PULL
VCO
UP
Down
Ipd
Vcntrl Vout
CLOCK
BUFFER
DIVIDE BY 8
DIVIDE BY 9
4X1 MUX

6. TEAM CONTRIBUTION
Schematics & Simulation :
 Phase Detector , Push-Pull Charge Pump – Himakar Gaddam
 Loop filter ,Voltage Control Oscillator , Clock Buffer - Sam Vivin Raj
 Frequency Divider , Multiplexer - Narendra Naidu
Overall Simulation and test bench – Sam , Himakar , Narendra

7. DPLL – DESIGN CALCULATIONS
 fin = 100MHz; fout = 1GHz; Supply Voltage = 1.62V; Process - SS
 Loop Bandwidth – ωn
ωn = ωin/50 = 2πfin/50 = 12.57Mrad/sec
Damping Factor – ζ
 C = 10pF, C2 = C/10 = 1pF
 ζ = 1.25 (Slightly over damped, almost critically damped)
 ζ = 0.5ωnRC
 R = ζ/(0.5ωnC)
 R = 19.9KΩ (in loop filter)

8. Contd..
For 5 stage VCO;
Vin = Vctrl =(1.62 + 0.47) / 2 = 1.045V
N = 5, VDD = 1.62V, Vth = 0.47V
ID = 52.97 μA
R = 10.86kΩ;
Kvco = 475Mhz/V ( from the simulation)
6C = 6.54fF;

9. Contd..
where N = 10 =
Icp = 33.26μA
Rlarge =34.57Ω

10. MAJOR BLOCKS SCHEMATIC, TESTBENCH
AND SIMULATIONS

11. PHASE DETECTOR
Desired Parameters:
fin = 100MHz;
fout = 1GHz; fout/10 = 100MHz
fout = 900MHz; fout/9 = 100MHz
fout = 800MHz; fout/8 = 100MHz
During testing
• fclkA = 100MHz
• fclkb = 95MHz

12. PHASE DETECTOR
SCHEMATIC:

13. PHASE DETECTOR
TEST BENCH:
load

14. PHASE DETECTOR
SIMULATION RESULTS:
Fin=100MHz
Fout =95MHz
UP
DOWN

15. Push – Pull Charge pump
Desired parameters :
 For 5 stage VCO;
Kvco = 475MHz/V
 Push pull charge pump
Icp = 33.26μA
Rlarge = 34.57kΩ

16. PUSH-PULL CHARGE PUMP
SCHEMATIC:
Rlarge = 34.57K ohms
Rlarge
UP BAR
DOWN

17. PUSH-PULL CHARGE PUMP
TEST BENCH:
UPBAR
DOWN
Load
UP BAR
DOWN
Load

18. PUSH-PULL CHARGE PUMP
SIMULATION RESULTS:
Ipd
UPBAR
DOWN
Icp
DOWN
UP
Vcntl

19. Vcntl = 1.045V

20. Loop Filter
Desired Parameters :
 Capacitance(C) = 10pF, C2 = 1pF
 Loop Bandwidth – ωn
ωn = 12.57Mrad/sec
 Damping Factor – ζ
ζ = 1.25 (Slightly over damped, almost critically
damped)
R = 19.9kΩ

21. LOOP FILTER SCHEMATIC

22. Voltage Controlled Oscillator(VCO)
Desired Parameters :
For 5 stage VCO;
Vin = Vctrl =(1.62 + 0.47) / 2 = 1.045V
N = 5, VDD = 1.62V, Vth = 0.47V
ID = 52.97 μA
R = 10.86kΩ;
Kvco = 475Mhz/V
6C = 6.54fF;

23. VOLTAGE-CONTROLLED OSCILLATOR
SCHEMATIC:
R = 6.39K ohms
Vcntrl = 1.045 V
VDD = 1.62V ; VSS = 0

24. VOLTAGE CONTROL OSCILLATOR
TEST BENCH:

25. VOLTAGE CONTROL OSCILLATOR
SIMULATION RESULTS:
Freq = 1GHz

26. VOLTAGE CONTROL OSCILLATOR
SIMULATION RESULTS:
Kvco = 475Mhz/V

27. VOLTAGE CONTROL OSCILLATOR
SIMULATION RESULTS:
Freq = 900MHzR = 8.62K ohms
Vcntrl = 1.045 V
VDD = 1.62V ; VSS = 0

28. VOLTAGE CONTROL OSCILLATOR
SIMULATION RESULTS:
Kvco = 596Mhz/V

29. VOLTAGE CONTROL OSCILLATOR
SIMULATION RESULTS:
R = 11.17K ohms
Vcntrl = 1.045 V
VDD = 1.62V ; VSS = 0
Freq = 800MHz

30. Kvco = 663Mhz/V
VOLTAGE CONTROL OSCILLATOR
SIMULATION RESULTS:

31. CLOCK BUFFER
Design:
H=Cout / Cin = 10pF/3.27fF = 3058.1
G = 1, B = 1
F = GBH = 1*1*3058.1 = 3058.1. Taking ρ= 4;
N = Log43058 = 5.789
N = 6 stages
= 3.81

32. CLOCK BUFFER TEST BENCH
SCHEMATIC:

33. Clock Buffer Test Bench
Test bench:

34. CLOCK BUFFER TEST BENCH
SIMULATION RESULTS:
IN

35. Frequency Divider
Design :
 Divide by 10,9,8
 Components used:
XOR Gate , Nor2x1 , Nand2x1
Flip – Flops
AND Gate

36. DIVIDE BY 10 CIRCUIT
SCHEMATIC:

37. DIVIDE BY 10 CIRCUIT
TEST BENCH:

38. DIVIDE BY 10 CIRCUIT
SIMULATION RESULT:

39. DIVIDE BY 9 CIRCUIT
SCHEMATIC:

40. DIVIDE BY 9 CIRCUIT
TEST BENCH:

41. DIVIDE BY 9 CIRCUIT
SIMULATION RESULT:

42. DIVIDE BY 8 CIRCUIT
SCHEMATIC:

43. DIVIDE BY 8 CIRCUIT
TEST BENCH:

44. DIVIDE BY 8 CIRCUIT
SIMULATION RESULT:

45. 4X1 MULTIPLEXER :
SCHEMATIC :

46. 4X1 MULTIPLEXER :
TESTBENCH :

47. 4X1 MULTIPLEXER :
WAVEFORM 1 : S0 = 1; S1 = 0
Y = D1 = In2

48. 4X1 MULTIPLEXER :
WAVEFORM 2 :
S0 = 0; S1 = 1
Y = D2 = In3

49. 4X1 MULTIPLEXER :
WAVEFORM 3 :
S0 = 0; S1 = 0
Y = D0 = In1

50. SIMULATION OF ENTIRE PROJECT

51. DIGITAL PHASE LOCKED LOOP
SCHEMATIC:

52. DIGITAL PHASE LOCKED LOOP
TEST BENCH: Load = 10pF

53. DIGITAL PHASE LOCKED LOOP IN LOCK
SIMULATIONS: Freq = 1GHz
Process corner –> SS; VDD –> 1.62; T = 125C

54. DIGITAL PHASE LOCKED LOOP IN LOCK
SIMULATIONS: Freq = 1GHz
Process corner –> tt; VDD –> 1.8; T = 27C

55. DIGITAL PHASE LOCKED LOOP IN LOCK
SIMULATIONS:
Freq = 900MHz
Process corner – SS; VDD – 1.62; T = 125C

56. DIGITAL PHASE LOCKED LOOP IN LOCK
SIMULATIONS: Freq = 800Hz
Process corner –> SS; VDD –> 1.62; T = 125C

57. Results
Fout = 1GHz Fout = 900Mhz Fout = 800Mhz
Vcntl 1.045 1.045 1.045
Frequency divider N = 10 N = 9 N =8
Icp 33.26μA 23.85μA 19.1μA
Rlarge 34.57Kohm 48.21Kohm 60.20Kohm
R at VCO 6.39Kohm 8.62Kohm 11.17Kohm
At Process Corner – SS ; VDD – 1.62 ; T = 125’C

58. CHALLENGES
 Adjusting R in VCO to get the required Frequency
 Frequency dividers for divide by 9,10 circuits

59. Thank you