We've got a couple of AD9361 PCB design questions that I figured would be best to bundle into a single post.
1) What is the maximum TX and RX data trace slack, assuming the maximum sample rate of 61.44Msps? In other words, what is the maximum length/TOF delay between A_P1_D0, A_P1_D1, A_P1_D2, etc...
2) What is the recommended bypass capacitor configuration? Right now we're using the ADP1755 with a configuration of ferrite -> 0.1uF -> small power plane (to minimize parasitic inductance) for all 1.3V digital and analog supplies. Does adding a 10uF capacitor or doing 0.1uF -> ferrite -> 0.1uF -> power plane significantly improve the 9361's performance?
3) What is the nominal peak-to-peak voltage for the SYNC_IN signal? We couldn't much information on this in the wiki or datasheet.
1. Please refer UG-570 for data timing constrains . (table 49, CMOS and table 51 for LVDS)
2. You can refer , Evaluation board reference schematics for reference. Additional filtering requirements will be benificial if your board has other digital parts other than AD9361.
3. Will get back on the level for sync_in. It should be same as reference clock. Sync_in details are available in UG-570 section under BASEBAND SYNCHRONIZATION.
Thanks, Vinod. A couple of follow-ups:
1) We saw table 49 - it's helpful for determining clock-data requirements, but not data-data. Our current design has 10mm of TOF delay between two of the P0 bus pins, for example. Is within acceptable timing parameters for the AD9361, CMOS mode?
2) The evaluation board uses 0201 capacitors, if I am not mistaken - we're trying to avoid 0201 components to minimize manufacturing cost, hence our current design.
3) We saw that section but did not find any information on p2p voltage. I assumed it should be equal to 1.3V but wanted to make sure.
1. From UG 570:
Transmit data is driven on P0_D[11:6] by the BBP such that the setup and hold times between FB_CLK and P0_D[11:6] allow the AD9361 to use FB_CLK to capture the data. Receive data is driven on P0_D[5:0] by the AD9361 such that the setup and hold times between DATA_CLK and P0_D[5:0] arriving at the BBP enable the BBP to use DATA_CLK to capture the data
Each data line has to meet the individual timing requirement as specified .
Please refer below link for interface tuning.
Digital Interface Timing Verification [Analog Devices Wiki]
2. 0402 components will have lower ESR and can be placed closer to the pins. You can use any package for decaps . Care must be taken in their placement.
3. yes it is 1.3V.
Great, this works for us. Thanks, Vinod.