Wow, this baby is complex.
Read this first…L6470 presentation

I bought two eval kits from digikey/mouser $25 each. (mouser: 511-EVAL6470H-DISC )
It  has a USB interface, JTAG interface and some buttons. The eval software for the board is  comprehensive. There is alot to this chip- it is NOT for the non engineering types.

It is not just a fancy bridge driver, it is a stepper /motion control ‘co-processor’ you tell it where you want to go and it goes and manages it… SPI interface…

In a nutshell- on my steppers this chip is smooth. I mean REALLY smooth on microsteps.
it uses Voltage Mode drive (rather than current mode drive) with BEMF compensation, and from my non stepper standpoint, voltage drive is much preferable for driving this sort of device.

I have steppers clamped to my steel bench for eval, so any vibration gets amplified through the bench…. I tested steppers with inertial load, and without.

The results are chalk-and-cheese against my other stepper drivers 8825, 6620 etc.This chip does not want to do anything BUT microsteps. I found compared to the other drivers, the microsteps were pretty much within the 5% of a full step tolerance.

and, as expected, the microstep performance was vastly improved by having some sort of load on the shaft. This is why i think the component rotation application is going poorly for some users  – no load and undamped resonances and vibrations. IE needs a chunk of steel on the shaft.
(And even worse with the abrupt current mode chopper drivers I am used to_

Its a good eval kit (Discovery kit), but before you start, you MUST read at least the eval datasheet, the eval software manual, upgrade the software on the board etc.

Then you MUST READ (because results will be disappointing otherwise)  AN4144. I say again. MUST READ.

Then be sure to read AN4241, UM1691, AN3991, then, optionally, AN4290, DT0055, DT0056.