250 MHz Bandwidth
DPD Observation Receiver
AD6641
FEATURES
GENERAL DESCRIPTION
SNR = 65.8 dBFS at fIN up to 250 MHz at 500 MSPS
ENOB of 10.5 bits at fIN up to 250 MHz at 500 MSPS (−1.0 dBFS)
SFDR = 80 dBc at fIN up to 250 MHz at 500 MSPS (−1.0 dBFS)
Excellent linearity
DNL = 0.5 LSB typical, INL = 0.6 LSB typical
Integrated 16k × 12 FIFO
FIFO readback options
12-bit parallel CMOS at 62.5 MHz
6-bit DDR LVDS interface
SPORT at 62.5 MHz
SPI at 25 MHz
High speed synchronization capability
1 GHz full power analog bandwidth
Integrated input buffer
The AD6641 is a 250 MHz bandwidth digital predistortion
(DPD) observation receiver that integrates a 12-bit 500 MSPS
ADC, a 16k × 12 FIFO, and a multimode back end that allows
users to retrieve the data through a serial port (SPORT), the SPI
interface, a 12-bit parallel CMOS port, or a 6-bit DDR LVDS
port after being stored in the integrated FIFO memory. It is opti-
mized for outstanding dynamic performance and low power
consumption and is suitable for use in telecommunications
applications such as a digital predistortion observation path
where wider bandwidths are desired. All necessary functions,
including the sample-and-hold and voltage reference, are
included on the chip to provide a complete signal conversion
solution.
The on-chip FIFO allows small snapshots of time to be captured
via the ADC and read back at a lower rate. This reduces the
constraints of signal processing by transferring the captured
data at an arbitrary time and at a much lower sample rate. The
FIFO can be operated in several user-programmable modes. In
the single capture mode, the ADC data is captured when sig-
naled via the SPI port or the use of the external FILL pins. In
the continuous capture mode, the data is loaded continuously
into the FIFO and the FILL pins are used to stop this operation.
On-chip reference, no external decoupling required
Low power dissipation
695 mW at 500 MSPS
Programmable input voltage range
1.18 V to 1.6 V, 1.5 V nominal
1.9 V analog and digital supply operation
1.9 V or 3.3 V SPI and SPORT operation
Clock duty cycle stabilizer
Integrated data clock output with programmable clock and
data alignment
APPLICATIONS
Wireless and wired broadband communications
Communications test equipment
Power amplifier linearization
FUNCTIONAL BLOCK DIAGRAM
FILL+ FILL– DUMP
CLK+
CLK–
CLOCK AND CONTROL
PCLK+
PCLK–
PARALLEL
VIN+
VIN–
PD[5:0]± IN DDR LVDS MODE
OR PD[11:0] IN CMOS MODE
AND
SPORT
OUTPUTS
FIFO
16k × 12
ADC
SP_SCLK
SP_SDFS
SP_SDO
SPI CONTROL
AND DATA
REFERENCE
FULL
EMPTY
VREF
SCLK, SDIO, AND CSB
Figure 1.
Rev. 0
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