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TPS546A24A: The reason of differtial output voltage sense and PMBus

Part Number: TPS546A24A

Hi expert,

Two simple questions below:

1. I notice that all this 'SWIFT' series buck converters, have differtial sense of Vo, e.g. TPS546A24, what is the reason for it? Why not use single-end voltage sense like typical buck converter? 

2. Why we add PMBus only for high output current 'SWIFT' buck converters? What it the typical load type for PoL, when PMBus is needed? 


    1) Differential Remote Sense, or Remote Sense is often added to higher performance converters where output voltage regulation accuracy is important and the effects of voltage drop, either in the primary power path (VOUT) or in the return (GND) could affect regulation accuracy.  As system consumption currents have increased and critical supply voltages have decreased, the performance and noise margin impacts of voltage measurements errors have become greater while the design margins for them have gotten smaller.

    As little as 10 years ago, Remote Sense features were often limited to very high current application delivering tens to even hundreds of Amperes of current, but as time and technology have progresses, the need for precision supply voltage regulation has increased.  While a low current I/O rail might not deliver a large current, a core supply that does could be located between critical load and the I/O's supply converter, so the high ground current from the core creates a shift in the ground at the critical device and single-ended monitoring and regulation of the output voltage can not compensate for this ground shift.

    2) Digital interfaces such as I2C, PMBus, AVSVBus and others add interface pins, silicon area and design complexity that adds cost to the device.  As a result, devices with digital interfaces have higher prices associated with them.  The value of having PMBus increases with the total power of the rail while the percentage overhead cost decreases as the cost to support higher currents increases, so the focus for PMBus solutions has started at the higher current applications, especially Core processor supply voltages where output voltage adjustment (AVS) offers greater return in terms of optimizing power dissipation and utilization (efficiency)

    As the technology has increased and the added cost and complexity has decreased the currents were digital interface solutions like PMBus have decreased, like the TPS546A24A.