AD6655BCPZ-125 Analog Devices Inc, AD6655BCPZ-125 Datasheet - Page 60

• Manufacturer Part Number: AD6655BCPZ-125
• Description: IC IF RCVR 14BIT 125MSPS 64LFCSP
• Manufacturer: Analog Devices Inc

Specifications of AD6655BCPZ-125

• Function: IF Diversity Receiver
• Frequency: 450MHz
• Rf Type: Cellular, CDMA2000, GSM EDGE, W-CDMA
• Secondary Attributes: 32-Bit Numerically Controlled Oscillator
• Package / Case: 64-VFQFN, CSP Exposed Pad
• Receiving Current: 705mA
• Frequency Range: 450MHz
• Rf Ic Case Style: LFCSP
• No. Of Pins: 64
• Supply Voltage Range: 1.7V To 1.9V
• Operating Temperature Range: -40°C To +85°C
• Frequency Max: 650MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD6655-125EBZ - BOARD EVAL W/AD6655 & SOFTWARE
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD6655
To avoid this additional DRVDD current, the AD6655 outputs
can be disabled at power-up by taking the OEB pin high. After
the part is placed into LVDS mode via the SPI port, the OEB
pin can be taken low to enable the outputs.
Exposed Paddle Thermal Heat Slug Recommendations
It is mandatory that the exposed paddle on the underside of the
ADC be connected to analog ground (AGND) to achieve the
best electrical and thermal performance. A continuous, exposed
(no solder mask) copper plane on the PCB should mate to the
AD6655 exposed paddle, Pin 0.
The copper plane should have several vias to achieve the lowest
possible resistive thermal path for heat dissipation to flow through
the bottom of the PCB. These vias should be filled or plugged with
nonconductive epoxy.
To maximize the coverage and adhesion between the ADC
and the PCB, a silkscreen should be overlaid to partition the
continuous plane on the PCB into several uniform sections.
This provides several tie points between the ADC and the PCB
during the reflow process. Using one continuous plane with no
partitions guarantees only one tie point between the ADC and
the PCB. See the evaluation board for a PCB layout example.
For detailed information about packaging and PCB layout of
chip scale packages, refer to Application Note AN-772, A Design
and Manufacturing Guide for the Lead Frame Chip Scale Package
(LFCSP) (see www.analog.com).
Rev. A | Page 60 of 88
CML
The CML pin should be decoupled to ground with a 0.1 μF
capacitor, as shown in Figure 48.
RBIAS
The AD6655 requires that a 10 kΩ resistor be placed between
the RBIAS pin and ground. This resistor sets the master current
reference of the ADC core and should have at least a 1% tolerance.
Reference Decoupling
The VREF pin should be externally decoupled to ground with
a low ESR, 1.0 μF capacitor in parallel with a low ESR, 0.1 μF
ceramic capacitor.
SPI Port
The SPI port should not be active during periods when the full
dynamic performance of the converter is required. Because the
SCLK, CSB, and SDIO signals are typically asynchronous to the
ADC clock, noise from these signals can degrade converter
performance. If the on-board SPI bus is used for other devices,
it may be necessary to provide buffers between this bus and the
AD6655 to keep these signals from transitioning at the converter
inputs during critical sampling periods.