AD9522-5BCPZ Analog Devices Inc, AD9522-5BCPZ Datasheet - Page 34

• Manufacturer Part Number: AD9522-5BCPZ
• Description: 12- Channel Clock Generator With Integra
• Manufacturer: Analog Devices Inc
• Type: Clock Generator, Fanout Distributionr

Specifications of AD9522-5BCPZ

• Pll: Yes
• Input: CMOS, LVDS, LVPECL
• Output: CMOS, LVDS
• Number Of Circuits: 1
• Ratio - Input:output: 2:12, 2:24
• Differential - Input:output: Yes/Yes
• Frequency - Max: 2.4GHz
• Divider/multiplier: Yes/No
• Voltage - Supply: 3.135 V ~ 3.465 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LFCSP
• Frequency-max: 800MHz
• Ic Interface Type: I2C, SPI
• Frequency: 2.4GHz
• No. Of Outputs: 12
• No. Of Multipliers / Dividers: 4
• Supply Voltage Range: 3.135V To 3.465V
• Digital Ic Case Style: LFCSP
• No. Of Pins: 64
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9522-5
Automatic/Internal Holdover Mode
When enabled, the automatic/internal holdover mode auto-
matically puts the charge pump into a high impedance state
when the loop loses lock. The assumption is that the only
reason that the loop loses lock is due to the PLL losing the
reference clock; therefore, the holdover function puts the charge
pump into a high impedance state to maintain the VCO
frequency as close as possible to the original frequency before
the reference clock disappeared.
A flowchart of the automatic/internal holdover function
operation is shown in Figure 34.
HIGH IMPEDANCE
HIGH IMPEDANCE
WHEN DLD WENT
LD PIN == HIGH
CHARGE PUMP
CHARGE PUMP
EDGE AT PFD?
PLL ENABLED
DLD == HIGH
DLD == LOW
REFERENCE
RELEASE
LOW?
WAS
YES
YES
YES
Figure 34. Flowchart of Automatic/Internal Holdover Mode
NO
NO
NO
NO
YES
Rev. 0 | Page 34 of 76
LOOP OUT OF LOCK. DIGITAL LOCK
DETECT SIGNAL GOES LOW WHEN THE
LOOP LEAVES LOCK AS DETERMINED
BY THE PHASE DIFFERENCE AT THE
INPUT OF THE PFD.
ANALOG LOCK DETECT PIN INDICATES
LOCK WAS PREVIOUSLY ACHIEVED.
(0x01D[3] = 1; USE LD PIN VOLTAGE
WITH HOLDOVER.
0x01D[3] = 0; IGNORE LD PIN VOLTAGE,
TREAT LD PIN AS ALWAYS HIGH.)
CHARGE PUMP IS MADE
HIGH IMPEDANCE.
PLL COUNTERS CONTINUE
OPERATING NORMALLY.
CHARGE PUMP REMAINS HIGH
IMPEDANCE UNTIL THE REFERENCE
RETURNS.
TAKE CHARGE PUMP OUT OF
HIGH IMPEDANCE. PLL CAN
NOW RESETTLE.
WAIT FOR DLD TO GO HIGH. THIS TAKES
5 TO 255 CYCLES (PROGRAMMING OF THE DLD
DELAY COUNTER) WITH THE REFERENCE AND
FEEDBACK CLOCKS INSIDE THE LOCK WINDOW AT
THE PFD. THIS ENSURES THAT THE HOLDOVER
FUNCTION WAITS FOR THE PLL TO SETTLE AND LOCK
BEFORE THE HOLDOVER FUNCTION CAN BE
RETRIGGERED.
The holdover function senses the logic level of the LD pin as a
condition to enter holdover. The signal at LD can be from the
DLD, ALD, or current source LD (CSDLD) mode. It is possible
to disable the LD comparator (0x01D[3]), which causes the hold-
over function to always sense LD as being high. If DLD is used,
it is possible for the DLD signal to chatter while the PLL is
reacquiring lock. The holdover function may retrigger, thereby
preventing the holdover mode from terminating. Use of the
current source lock detect mode is recommended to avoid this
situation (see the Current Source Digital Lock Detect (CSDLD)
section).