ADF4355

Comparing the "Features" block on the first page

of the two data sheets reveals the following lines

that are different:

ADF4355:

RF output frequency range: 54 MHz to 6800 MHz

Analog and digital power supplies: 3.3 V

Charge pump and VCO power supplies: 5.0 V typical

ADF4355-3:

RF output frequency range: 51.5625 MHz to 6600 MHz

All power supplies: 3.3 V

The "General Description" block on the right-hand side

of the data sheet reveals the following sentences that are

different (and also add new information):

ADF4355:

The ADF4355 has an integrated VCO with a fundamental output frequency ranging from 3400 MHz to 6800 MHz.

The ADF4355 operates with analog and digital power supplies ranging from 3.15 V to 3.45 V, with charge pump and VCO supplies from 4.75 V to 5.25 V

ADF4355-3:

The ADF4355-3 has an integrated VCO with a fundamental output frequency ranging from 3300 MHz to 6600 MHz

The ADF4355-3 operates with analog, digital, charge pump, and VCO power supplies ranging from 3.1515 V to 3.4485 V

Comparing the "Features" block on the first page

of the two data sheets reveals the following lines

that are different:

ADF4355:

RF output frequency range: 54 MHz to 6800 MHz

Analog and digital power supplies: 3.3 V

Charge pump and VCO power supplies: 5.0 V typical

ADF4355-3:

RF output frequency range: 51.5625 MHz to 6600 MHz

All power supplies: 3.3 V

The "General Description" block on the right-hand side

of the data sheet reveals the following sentences that are

different (and also add new information):

ADF4355:

The ADF4355 has an integrated VCO with a fundamental output frequency ranging from 3400 MHz to 6800 MHz.

The ADF4355 operates with analog and digital power supplies ranging from 3.15 V to 3.45 V, with charge pump and VCO supplies from 4.75 V to 5.25 V

ADF4355-3:

The ADF4355-3 has an integrated VCO with a fundamental output frequency ranging from 3300 MHz to 6600 MHz

The ADF4355-3 operates with analog, digital, charge pump, and VCO power supplies ranging from 3.1515 V to 3.4485 V

Thanks. But the differences seem to me to be insufficient to warrant a separate chip design!

It's unlikely the ADF4355-3 required a new photomask set.

Modern mixed-signal chips have ways to permanently

modify the behavior of the chip post-fabrication [1].

What likely happened here was that a customer wanted to

use the ADF4355 in a design that did not have a 5V rail available,

and asked ADI if it was possible to trim a version of the chip that

worked with all rails at 3.3V with reduced specifications.  Once

the work was done, there was no reason not to offer the chip

variant to the entire customer base. 

[1] www.analog.com/.../digitrim-technology.html