AD9518-0_15 Datasheet, PDF (24/64 Pages) Analog Devices – 6-Output Clock Generator with Integrated 2.8 GHz VCO

AD9518-0
Data Sheet
Internal VCO and Clock Distribution
When using the internal VCO and PLL, the VCO divider must
be employed to ensure that the frequency presented to the channel
dividers does not exceed their specified maximum frequency of
1600 MHz (see Table 3). The internal PLL uses an external loop
filter to set the loop bandwidth. The external loop filter is also
crucial to the loop stability.
When using the internal VCO, it is necessary to calibrate the
VCO (Register 0x018[0]) to ensure optimal performance.
For internal VCO and clock distribution applications, use the
register settings that are shown in Table 23.
Table 23. Settings When Using an Internal VCO
Register
Function
0x010[1:0] = 00b PLL normal operation (PLL on).
0x010 to 0x01D PLL settings. Select and enable a reference
input; set R, N (P, A, B), PFD polarity, and ICP
according to the intended loop configuration.
0x018[0] = 0b, Reset VCO calibration. This process is not
0x232[0] = 1b required the first time after power-up, but it
must be performed subsequently.
0x1E0[2:0]
Set VCO divider to divide-by-2, divide-by-3,
divide-by-4, divide-by-5, or divide-by-6.
0x1E1[0] = 0b Use VCO divider as the source for the
distribution section.
0x1E1[1] = 1b Select VCO as the source.
0x018[0] = 1b, Initiate VCO calibration.
0x232[0] = 1b
REF_ SEL
VS GND
RSET
REFMON
REFIN (REF1)
REFIN (REF2)
BYPASS
LF
CLK
CLK
PD
SYNC
RESET
REF1
REF2
REFERENCE
SWITCHOVER
STATUS
STATUS
LOW DROPOUT
REGULATOR (LDO)
VCO
DIGITAL
LOGIC
DISTRIBUTION
REFERENCE
R
DIVIDER
VCO STATUS
P, P + 1
PRESCALER
A/B
COUNTERS
N DIVIDER
PROGRAMMABLE
R DELAY
PROGRAMMABLE
N DELAY
DIVIDE BY
2, 3, 4, 5, OR 6
10
DIVIDE BY
1 TO 32
SCLK
SDIO
SDO
CS
SERIAL
CONTROL
PORT
DIVIDE BY
1 TO 32
DIVIDE BY
1 TO 32
AD9518-1
CPRSET VCP
LOCK
DETECT
PHASE
FREQUENCY
DETECTOR
HOLD
CHARGE
PUMP
LVPECL
LVPECL
LVPECL
Figure 29. Internal VCO and Clock Distribution
LD
CP
STATUS
OUT0
OUT0
OUT1
OUT1
OUT2
OUT2
OUT3
OUT3
OUT4
OUT4
OUT5
OUT5
Rev. C | Page 24 of 64