JESD204B serial interface has 3 subclasses called Sub class 0 , sub | ||
Analog Interface needs for RF Sampling data converters : |
class 1 and sub class 2 . Sub class 2 uses SYNC as timing signal and due to SYNC timing constraints , it can be used only for data |
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As the RF sampling ADCs handling the direct RF input frequencies , |
converters sampling rates upto 500MSPS . For RF sampling ADCs |
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the input stage of the ADCs needs to handle very high |
and DACs , the sub class1 which uses the SYSREF is required . |
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frequencies . The high speed Amplifier ( ex . LMH5401 or |
Deterministic Latency is supported in JESD204B subclass 1 and 2 |
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LMH6401 ) or Balun is typically used in the front end stage of ADC |
which is critical for applications like beam forming etc . where |
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for converting the single ended input to differential conversion |
multiple data converters are used in the system and |
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and similarly for DAC output stage for differential to single ended |
synchronization between these multiple data converters is |
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conversion . There are tradeoffs between using the |
needed . The inherent advantage of JESD204B is that they are no |
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Balun / transformer Vs Amplifier for this purpose and the designer |
length matching requirements for the data outputs from ADC to |
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needs to carefully select between these two options based on the |
processor / FPGA . |
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system performance tradeoffs . Baluns are not suited for wide bandwidth and it will have large insertion loss and varies with frequency compared to wideband high speed amplifiers . Baluns doesn ’ t have any power gain as impedance matching and voltage / current gain are dependent whereas amplifiers supports power gain as impedance matching and gain are independent .
Amplifiers provide buffering whereas Baluns require previous stage to drive filter and ADC input load . But Amplifier adds noise
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The clocking is important device for JESD204B data converters clocking along with clocking FPGA / processor by providing Device clock and SYSREF clock . TI LMK0482x clocking devices are specifically designed for this purpose and widely used in the industry for JESD204B clocking .
How system designers can quick start designs with RF sampling ADCs ?
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compared to Balun . The selection between the Balun and |
There are multiple TI reference designs using RF sampling ADCs |
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Amplifier needs to be done based on the above parameters and |
and DACs interfacing with FPGAs / processor . Many technical |
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system performance tradeoffs for interfacing with the specific |
publications , application notes are also available to understand |
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ADC and DAC . |
JESD204B interface and deterministic latency and designing the |
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Digital Interface needs for RF Sampling data converters :
As these RF sampling ADCs and DACs have sampling rates of
4GSPS and beyond , traditional LVDS interface will not be possible to connect these data converters with Processors and FPGAs . For examples , ADC32RF45 is a 14 bit 3GSPS dual Channel ADC . LVDS interface cannot directly support 3gsps interface speed . We need to have new interface type which can support these high data rates . The JESD204B serial interface is developed for solving this interface problem . ADC output or DAC input can connect with
FPGA or Processors over JESD204B interface with the speeds upto
12.5Gbps as per present standard and the speeds might be enhanced further in future as the data converter speeds are going
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solutions to achieve deterministic latency . The following are some of the examples of reference designs .
1 .
TIDEP00081 : TI Design showing Wideband receiver solution using TI processor 66AK2L06 ( multicore processor DSP + ARM ) interfacing directly with ADC32RF80 over JESD204B
( http :// www . ti . com / tool / tidep0081 ).
2 .
TIDA-00826 : TI Design with RF sampling ADC and its analog front end solution using High speed Amplifiers
( http :// www . ti . com / tool / TIDA-00826 ).
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TIDA-00432 : TI Design showing the synchronization of
JESD204B Giga sample ADC with FPGA for Phased array radar systems ( http :// www . ti . com / tool / TIDA-00432 ).
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to increase further in coming years . Texas Instruments is fully |
The following application notes will be useful for understanding |
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committed to this new interface standard and offers a compelling |
the JESD204B interface , its benefits , deterministic latency and |
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data converter roadmap with state of the art devices to support |
usage for high speed data converters . |
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it . The application note SLYY057B ( www . ti . com / lit / SLYY057 ) |
1 . |
SLYT628 : JESD204B multi-device synchronization : Breaking |
provides the details on what all you need to know while you are |
down the requirements . |
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transitioning to JESD204B interface . |
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JESD Blog stories : This has very useful JESD204B based blogs |
In LVDS and CMOS systems , package size , board area and power |
for system designers . |
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consumption dominated by output buffers rather than the data |
http :// e2e . ti . com / tags / JESD204B % 2bseries |
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converter itself . JESD204B Interface key benefit over existing |
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LVDS / CMOS interface is reduced IC package pin count for data |
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