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LM51772 Buck-Boost controller I2C configuration


Hi all,

I'm planning on making a high power dc-dc buck boost converter mainly for powering LEDs and I found the LM51772 from TI which looks good. In order to configure different settings on the IC you use resistors on different pins but two of the configuration pins are also used for the I2C when its enabled. As I want to use the I2C on this chip i'm not sure how to configure it.

I was wondering if anyone else has had any experience with this controller or if you've used other IC's that are configured in a similar way?

Or if anyone has suggestions for a different Buck-Boost controller with similar specs? ideally has I2C communication.

I've attached a screenshot of the section from the datasheet where it talks about the CFG pins.

I started looking at it, and I have to say that is by far the worst data sheet I’ve ever seen from TI. :(

Have you also looked at the evaluation board? Those (or their documentation) sometimes explain things more clearly and succinctly than the data sheets. https://www.ti.com/tool/LM51772EVM-HP

For people who don't want to look at the datasheet the CFG3 and CFG4 pins which are used to configure different settings for the IC are shared with the I2C SCL and SDA pins.

After looking at the evaluation board I think that if you plan on using I2C with the IC then you just use CFG1 to enable I2C and then ignore any resistors for the R2D circuit on CFG3 and CFG4 for the IC settings. Just use a normal pull up resistor for normal I2C operation and then the settings which previously had to be configured using the pull down resistors on CFG3 and CFG4 can be changed using I2C.

I'm still not sure if this is actually how it works and as you've seen the datasheet is kind of a mess at the moment and I can't justify paying $400 AUD for an evaluation board. As it is a new IC there isn't any documentation on it other than the unfinished datasheet.

I might have to wait until there is more information or just find a different DC-DC converter.


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