AD9627-125EBZ Analog Devices Inc, AD9627-125EBZ Datasheet - Page 52

• Manufacturer Part Number: AD9627-125EBZ
• Description: 12Bit 125 Msps Dual 1.8V PB Free ADC
• Manufacturer: Analog Devices Inc

Specifications of AD9627-125EBZ

• Number Of Adc's: 2
• Number Of Bits: 12
• Sampling Rate (per Second): 125M
• Data Interface: Serial
• Inputs Per Adc: 1 Differential
• Input Range: 2 Vpp
• Power (typ) @ Conditions: 900mW @ 125MSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9627
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9627
DEFAULT OPERATION AND JUMPER SELECTION
SETTINGS
The following is a list of the default and optional settings or
modes allowed on the AD9627 evaluation board.
POWER
Connect the switching power supply that is provided in the
evaluation kit between a rated 100 V ac to 240 V ac wall outlet
at 47 Hz to 63 Hz and P500.
VIN
The evaluation board is set up for a double balun configuration
analog input with optimum 50 Ω impedance matching from
70 MHz to 200 MHz. For more bandwidth response, the differ-
ential capacitor across the analog inputs can be changed or
removed (see Table 13). The common mode of the analog inputs
is developed from the center tap of the transformer via the CML
pin of the ADC (see the Analog Input Considerations section).
VREF
VREF is set to 1.0 V by tying the SENSE pin to ground by adding
a jumper on Header J5 (Pin 1 to Pin 2). This causes the ADC to
operate in 2.0 V p-p full-scale range. To place the ADC in 1.0 V p-p
mode (VREF = 0.5 V), a jumper should be placed on Header J4.
A separate external reference option is also included on the evalua-
tion board. To use an external reference, connect J6 (Pin 1 to Pin 2)
and provide an external reference at TP5. Proper use of the VREF
options is detailed in the Voltage Reference section.
RBIAS
RBIAS requires a 10 kΩ resistor (R503) to ground and is used to
set the ADC core bias current.
CLOCK
The default clock input circuitry is derived from a simple balun-
coupled circuit using a high bandwidth 1:1 impedance ratio balun
(T5) that adds a very low amount of jitter to the clock path. The
clock input is 50 Ω terminated and ac-coupled to handle single-
ended sine wave inputs. The transformer converts the single-ended
input to a differential signal that is clipped before entering the
ADC clock inputs. When the AD9627 input clock divider is
utilized, clock frequencies up to 625 MHz can be input into the
evaluation board through Connector S5.
PDWN
To enable the power-down feature, connect J7, shorting the
PDWN pin to AVDD.
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CSB
The CSB pin is internally pulled up, setting the chip into
external pin mode, to ignore the SDIO and SCLK information.
To connect the control of the CSB pin to the SPI circuitry on the
evaluation board, connect J21, Pin 1 to J21, Pin 2.
SCLK/DFS
If the SPI port is in external pin mode, the SCLK/DFS pin sets the
data format of the outputs. If the pin is left floating, the pin is inter-
nally pulled down, setting the default data format condition to
offset binary. Connecting J2, Pin 1 to J2, Pin 2 sets the format to
twos complement. If the SPI port is in serial pin mode, connecting
J2, Pin 2 to J2, Pin 3 connects the SCLK pin to the on-board SPI
circuitry (see the Serial Port Interface (SPI) section).
SDIO/DCS
If the SPI port is in external pin mode, the SDIO/DCS pin sets
the duty cycle stabilizer. If the pin is left floating, the pin is
internally pulled up, setting the default condition to DCS enabled.
To disable the DCS, connect J1, Pin 1 to J1, Pin 2. If the SPI port
is in serial pin mode, connecting J1, Pin 2 to J1, Pin 3 connects
the SDIO pin to the on-board SPI circuitry (see the Serial Port
Interface (SPI) section).
ALTERNATIVE CLOCK CONFIGURATIONS
Two alternate clocking options are provided on the AD9627
evaluation board. The first option is to use an on-board crystal
oscillator (Y1) to provide the clock input to the part. To enable
this crystal, Resistor R8 (0 Ω) and Resistor R85 (10 kΩ) should
be installed, and Resistor R82 and Resistor R30 should be removed.
A second clock option is to use a differential LVPECL clock to
drive the ADC input using the
drive option, the AD9516 charge pump filter components need
to be populated (see Figure 79). Consult the AD9516 data sheet
for more information.
To configure the clock input from S5 to drive the AD9516
reference input instead of directly driving the ADC, the
following components need to be added, removed, and/or
changed.
1.
2.
In addition, unused AD9516 outputs (one LVDS and one LVPECL)
are routed to optional Connector S8 through Connector S11 on
the evaluation board.
Remove R32, R33, R99, and R101 in the default
clock path.
Populate C78 and C79 with 0.001 μF capacitors and
R78 and R79 with 0 Ω resistors in the clock path.
AD9516
(U2). When using this