LP8764-Q1: LP8764-Q1: what are the differences between B4 and B5 parts (LP876411B4RQKRQ1 and LP876411B5RQKRQ1) apart from the I2C addresses?

Hi Ishtiaque ,

Thanks for the update. One candid feedback from an end user perspective here is that it would have been much better if the differences in the orderable part numbers for this part had been specified in the datasheet itself, say as a brief note below the orderable information. I see at least 2 other forum entries for the same part with similar questions which indicates that many more people are likely suffering from the exact same confusion.

Having a brief note in the datasheet on the deltas would save the readers the difficulty of scanning across 2 separate 50 page plus documents to identify these deltas (actually I had already gone through and it was not exactly very straightforward since these docs have quite a lot of info so there was always this fear if I'm missing out on something).

Hope this feedback gets taken by TI in a constructive manner

Thanks,

Anoop

Hi Jari,

Thanks a lot for the extra clarification. Does this mean that "LP876411B5RQKRQ1" cannot be used in a standalone application? I was actually planning a standalone design with this unit, should I consider alternate parts if this cannot be used in this fashion?

Thanks,

Anoop

Hi Anoop,

Yes, power rail settings defined in LP876411B5RQKRQ1 doesn't match your requirement.  You can go through the user guide and see the configurations of the device. 

BR,

Ishtiaque 

Hi Ishtiaque,

I'm afraid it's not clear to me which power rail setting for LP876411B5RQKRQ1 doesn't meet my requirement. The spec sheet says that the input supply range is 2.8V to 5.5V which fits my application (I plan to give a 5V supply). Also the datasheet mentions output voltage: 0.3 V to 3.34 V (0.3 V to 1.9 V for multi-phase outputs) and Maximum output current: 5 A per phase, up to 20 A with 4-phase configuration, both of which meets my requirements as well.

So could you please elaborate on what aspects make this part unfit for my application of building a general purpose buck regulator with the input, output voltage and current specifications that are well within what's mentioned in the part datasheet?

Note that I plan to program the settings such as output voltages etc via the I2C interface and I do not plan to rely on the NVM settings per se.

Thanks,

Anoop

Hi Anoop,

Sorry I misunderstood then since I did not know about your requirements.  Of course, if general spec requirements are fitting to your requirements then you can use that in standalone. But there are  other settings such as power up sequencing , fault handling, interfacing selection such I2C or SPI that you want to look and see those also match your requirements or not. That's why this needs to be looked into more detail that what are your requirements from system level point of and how those can be met. May be your requirement in standalone application might differ than what LP876411B5RQKRQ1 is used for  J721S2.  May I know what is your application? what you will be powering up with LP876411B5RQKRQ1 ? 

BR,

Ishtiaque 

Hi Ishtiaque,

Thanks for the details. Basically my application just needs me to deliver a programmable supply voltage between 0.4V to 1.98V to my DUT which can draw up to 3A from this rail. The LP876411B5RQKRQ1 will be powered by a 5V supply available from an external DC jack that can drive up to 10A. The fact that this IC can deliver output voltages as low as 0.3V is what which really stood out in the choice of this part, and also the fact that it has remote IR drop sensing, pretty low output ripple specs and abilility to handle pretty big capacitive loads (up to 250uF per phase).

I had used a very similar buck (LP875610) very successfully in the past (in 4 phase single output mode) in a very similar application where the lowest voltage output requirement was 0.6V, but for my new application where I needed to deliver voltages as low as 0.4V I couldn't use the LP875610 whose minimum voltage spec was 0.6V, hence gravitated to LP876411B5RQKRQ1 which is rated for output voltages as low as 0.3V. I plan to use the 4 phase single output mode even here in order to maximize the current drive capability from the buck and also minimize the output ripple.

Thanks,

Anoop

Hi Ishtiaque,

I have capability of programming the configuration to any preferred supported configuration via I2C in my application and hence am not restrained by these NVM settings I suppose?

Thanks,

Anoop

Hi Anoop,

Thanks for your reply. I thought we are talking about big volumes here where it gets difficult to re-programmed the device until unless you have mechanism setup in production line which performs this task. What is the lifetime volume for this device use case?

And if you are able to do configuration then yes you can do that and if you already know how to do that. 

BR,

Ishtiaque 

Hi Ishtiaque,

This is not for volume production. The design I'm doing is purely for our in house testing in our lab of our test chips, basically as a programmable supply source (will probably have some 15-20 such boards or so only for internal usage). As such we are required to program the output supply levels for us to perform across supply voltage characterization of our test chips. So we do already have an infrastructure based on a micro-controller platform to perform the I2C programming as needed. We used the same approach without issues for the previous board design based on LP875610 and hope to follow something very similar with necessary modifications in settings programmed based on the register map details of the new part.

Thanks,

Anoop