AD9522-5BCPZ Analog Devices Inc, AD9522-5BCPZ Datasheet - Page 30

• 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
PLL External Loop Filter
An example of an external loop filter for a PLL is shown in
Figure 29. A loop filter must be calculated for each desired PLL
configuration. The values of the components depend on the VCO
frequency, the K
the desired loop bandwidth, and the desired phase margin. The
loop filter affects the phase noise, the loop settling time, and the
loop stability. A basic knowledge of PLL theory is necessary for
understanding loop filter design. ADIsimCLK can help with the
calculation of a loop filter according to the application requirements.
PLL Reference Inputs
The AD9522 features a flexible PLL reference input circuit that
allows a fully differential input, two separate single-ended inputs,
or a 16.62 MHz to 33.33 MHz crystal oscillator with an on-chip
maintaining amplifier. An optional reference clock doubler
can be used to double the PLL reference frequency. The input
frequency range for the reference inputs is specified in Table 2.
Both the differential and the single-ended inputs are self-biased,
allowing for easy ac coupling of input signals. To increase
isolation and reduce power, each single-ended input can be
independently powered down.
Either a differential or a single-ended reference must be specifically
enabled. All PLL reference inputs are off by default.
The differential input and the single-ended inputs share two pins,
REFIN (REF1) and REFIN (REF2). The desired reference input
type is selected and controlled by 0x01C (see
In single-ended mode, the AD9522 features a dc offset option.
Setting 0x018[7] to 1b shifts the dc offset bias point down 140 mV.
This option eliminates the risk of the reference inputs chattering
when they are ac-coupled and the reference clock disappears.
When using the reference switchover, the single-ended reference
inputs should be dc-coupled CMOS levels (with the AD9522 dc
offset feature disabled). Alternatively, the inputs can be ac-coupled,
and the dc offset feature can be enabled. The user should keep in
mind, however, that the minimum input amplitude for the
reference inputs is greater when the dc offset is turned on.
When the differential reference input is selected, the self-bias
level of the two sides is offset slightly to prevent chattering of
the input buffer when the reference is slow or missing. The
specification for this voltage level can be found in Table 2.
The input hysteresis increases the voltage swing required of
the driver to overcome the offset.
Figure 29. Example of External Loop Filter for PLL
AD9522
VCO
CHARGE
PUMP
, the PFD frequency, the charge pump current,
CLK/CLK
CP
C1
EXTERNAL
VCO/VCXO
R1
Table 43
C2
R2
C3
and
Table 47
Rev. 0 | Page 30 of 76
).
The differential reference input receiver is powered down when
it is not selected or when the PLL is powered down. The single-
ended buffers power down when the PLL is powered down or
when their respective individual power-down registers are set.
When the differential mode is selected, the single-ended inputs
are powered down.
In differential mode, the reference input pins are internally self-
biased so that they can be ac-coupled via capacitors. It is possible to
dc couple to these inputs. If the differential REFIN is driven by
a single-ended signal, the unused side ( REFIN ) should be
decoupled via a suitable capacitor to a quiet ground.
shows the equivalent circuit of REFIN.
Crystal mode is nearly identical to differential mode. The user
enables a maintaining amplifier by setting the enable XTAL OSC
bit, and putting a series resonant, AT fundamental cut crystal
across the REFIN/ REFIN pins.
Reference Switchover
The AD9522 supports dual single-ended CMOS inputs, as well
as a single differential reference input. In the dual single-ended
reference mode, the AD9522 supports automatic and manual
PLL reference clock switching between REF1 (on Pin REFIN)
and REF2 (on Pin REFIN ). This feature supports networking
and other applications that require hitless switching of
redundant references. When used in conjunction with the
automatic holdover function, the AD9522 can achieve a worst-
case reference input switchover with an output frequency
disturbance as low as 10 ppm.
REFIN
REFIN
REF1
REF2
Figure 30. REFIN Equivalent Circuit for Non-XTAL Mode
10kΩ
10kΩ
85kΩ
85kΩ
12kΩ
10kΩ
VS
VS
150Ω
150Ω
Figure 30
VS