How to read an analog and RF IP datasheet

Start with the conditions, not the headline

Every number on an IP datasheet belongs to a set of conditions. Supply voltage, temperature, process corner, load, frequency and source impedance all change the result. A noise figure measured at one bias and one temperature may not hold at the corner you need to ship.

So find the conditions table before you read the summary page. Then check that each number you care about is quoted under conditions close to your own. If it is not, write the question down and ask the vendor.

The fields that matter

• Process node and foundry: the IP only exists on the processes it was built for. Porting is a project, not a recompile.
• Area: the die area the block takes, including any required keep-out or guard ring.
• Supply: voltage range and current draw at the stated operating point.
• Bandwidth: the usable frequency range, and whether the edges are 3 dB points or something looser.
• Noise: input-referred noise density in nV per root hertz, or noise figure in dB, and at what frequency.
• Gain: in dB, with the load and the flatness across the band.
• Input range: the minimum and maximum signal level the block handles, in dBm or volts.
• Efficiency: for rectifiers and power amplifiers, how much input power ends up as useful output.
• Return loss (S11): how well the input is matched to the source impedance.

Noise units trip people up. Nanovolts per root hertz is a density: you multiply it by the square root of your bandwidth to get total noise. A part that is quiet per root hertz can still be loud over a wide band. Compare parts at your bandwidth, not at one frequency.

A worked example: Current RF's RF IP family

Current RF publishes datasheets for five RF blocks, the CC-201IP to CC-205IP. They make a good practice set because they cover amplifiers, inductors, power amplifiers and rectifiers. All figures below are the company's own, taken from its Radio Frequencies page, so treat them as claims to check against the datasheet.

• CC-201IP and CC-202IP: an ultra-low-noise single-cell amplifier family. The page lists approximately 30 dB of gain with 1.3 nV per root hertz noise, and for the CC-202IP about 70 dB with 8 nV per root hertz.
• CC-203IP: a super inductor. Current RF reports Q rising from 20% to over 100% of what typical on-chip inductors reach.
• CC-204IP: a power amplifier covering 6 MHz to 5.8 GHz, with a basic cell of 300 um by 400 um.
• CC-205IP: a wideband CMOS rectifier covering 6 MHz to 5.8 GHz, with an input range of -18 dBm to over +33 dBm, 40% to 90% conversion efficiency, and an S11 of -40 dB per the homepage.

Questions this example teaches

Look at the amplifier line. The 8 nV per root hertz figure is higher than 1.3 nV per root hertz, but the gain is higher too. A designer would ask whether the two figures belong to one part at different settings, or to two parts. The datasheet should answer that. If it does not, ask.

Look at the bandwidth too. The Radio Frequencies page gives the CC-202IP range as 200 MHz to 5.8 GHz in one place and 6 MHz to 5.8 GHz in another. That could reflect two operating modes or two settings. This is exactly the kind of gap you resolve by reading the datasheet's conditions table, and by writing to the vendor if it is still unclear.

The rectifier line has a range of -18 dBm to over +33 dBm, a span of more than 50 dB. Ask how the efficiency varies across that span. A single 40% to 90% range hides the shape of the curve. You want the plot, with the points marked where the part is spec'd.

For the inductor, ask what the Q is measured against, at what frequency, and with what substrate and metal stack. Q depends on all of them. A percentage comparison to typical on-chip inductors is only as useful as the reference it uses.

Check the process and the package of the IP itself

Ask for the process node the RF IP was characterized on. Current RF states that its CC-100 power IC is produced on the GlobalFoundries CM018RF process, and the datasheet for any given block should state its own. Ask what deliverables ship: layout views, a netlist, timing and noise models, a test report, and a list of verification runs.

Ask whether silicon data exists, and in what form. A simulation plot and a measured plot look alike on a datasheet. Only one of them comes from a part you can hold. Current RF says evaluation boards and reference designs are available on request, which is the practical way to turn a claim into a measurement of your own.

A short checklist

• Is every number tied to a stated supply, temperature and corner?
• Does the quoted bandwidth match the conditions for the gain and noise figures?
• Is the data simulation, silicon, or both, and does the sheet say which?
• Does the part work on your process, or is a port required?
• What do evaluation boards and reference designs cover?

The full set of RF IP datasheets, from the CC-201IP to the CC-205IP, is on the Datasheets page, and the block overview is on the Radio Frequencies page.