Datasheet

Data Sheet AD9557
Rev. B | Page 77 of 92
DPLL PROFILE REGISTERS (REGISTER 0x0700 TO REGISTER 0x0766)
Note that the default value of the REFA profile is as follows: input frequency = 19.44 MHz, output frequency = 622.08 MHz/155.52 MHz,
loop bandwidth = 400 Hz, normal phase margin, inner tolerance = 5%, and outer tolerance = 10%.
The default value of REFB profile is as follows: input frequency = 8 kHz, output frequency = 622.08 MHz/155.52 MHz, loop bandwidth =
100 Hz, normal phase margin, inner tolerance = 5%, and outer tolerance = 10%.
REFA Profile (Register 0x0700 to Register 0x0726)
Table 75. Reference Period—REFA Profile
Address Bits Bit Name Description
0x0700
[7:0] Nominal reference period (fs) Nominal reference period bits[7:0] (default: 0xC9)
0x0701
[7:0] Nominal reference period bits[15:8] (default: 0xEA)
0x0702 [7:0] Nominal reference period bits[23:16] (default: 0x10)
0x0703
[7:0] Nominal reference period bits[31:24] (default: 0x03)
0x0704
[7:0] Nominal reference period bits[39:32] (default: 0x00)
Default for Register 0x0700 to Register 0x0704 = 0x000310EAC9 = 51.44 ns (1/19.44 MHz)
Table 76. Reference Period Tolerance—REFA Profile
Address Bits Bit Name Description
0x0705
[7:0] Inner tolerance Input reference frequency monitor inner tolerance bits [7:0] (default: 0x14).
0x0706
[7:0] Input reference frequency monitor inner tolerance bit [15:8] (default: 0x00).
0x0707
[7:4] Reserved Reserved.
[3:0] Inner tolerance Input reference frequency monitor inner tolerance bits[19:16].
Default for Register 0x0705 to Register 0x0707 = 0x000014 = 20 (5% or 50,000 ppm).
The Stratum 3 clock requires inner tolerance of ±9.2 ppm and outer tolerance of ±12 ppm;
an SMC clock requires an outer tolerance of ±48 ppm.
The allowable range for the inner tolerance is 0x0000A (10%) to 0xFFFFF (1 ppm).
The tolerance of the input frequency monitor is only as accurate as the system clock
frequency.
0x0708
[7:0] Outer tolerance Input reference frequency monitor outer tolerance bits [7:0] (default: 0x0A).
0x0709
[7:0] Input reference frequency monitor outer tolerance bits[15:8] (default: 0x00).
0x070A [7:4] Reserved Reserved.
[3:0]
Outer tolerance Input reference frequency monitor outer tolerance bits[19:16] .
Default for Register 0x0708 to Register 0x070A = 0x00000A = 10 (10% or 100,000 ppm).
The Stratum 3 clock requires an inner tolerance of ±9.2 ppm and outer tolerance of
±12 ppm; an SMC clock requires an outer tolerance of ±48 ppm.
The outer tolerance register setting should always be smaller than the inner tolerance.
Table 77. Reference Validation Timer—REFA Profile
Address Bits Bit Name Description
0x070B
[7:0] Validation timer (ms) Validation timer bits[7:0] (default: 0x0A).
This is the amount of time a reference input must be valid before it is declared valid by
the reference input monitor (default: 10 ms).
0x070C [7:0] Validation timer bits[15:8] (default: 0x00).
Table 78. Reserved Register
Address Bits Bit Name Description
0x070D
[7:0] Reserved Default: 0x00
Table 79. DPLL Base Loop Filter Selection—REFA Profile
Address Bits Bit Name Description
0x070E
[7:1]
Reserved
Default: 0x00
0 Sel high PM base loop filter 0 = base loop filter with normal (70°) phase margin (default)
1 = base loop filter with high (88.5°) phase margin
(≤0.1 dB peaking in the closed-loop transfer function for loop bandwidths ≤ 2 kHz;
setting this bit is also recommended for loop bandwidths > 2kHz)