EYE ON NPI - Diodes Inc's AP3377 series USB PD3.1 Sink Controllers

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8d ago 9:47

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This week's EYE ON NPI will extend your power supply options, it's Diodes Inc's AP3377 series USB PD3.1 Sink Controllers (https://www.digikey.com/en/product-highlight/d/diodes/ap3377-usb-sink-controllers) a pair of chips that take the USB Type Power Delivery Sink specification to new highs with extended voltage ranges and two methods of configuration: the AP33772S (https://www.digikey.com/short/59d9mbvm) has I2C control interface while the AP33771C (https://www.digikey.com/short/022nd0fp) has two resistors to set the voltage and current limit. We've covered USB Power delivery sink controllers on EYE ON NPI before (https://www.digikey.com/short/59d9mbvm) with chips that can be configured to request higher voltages than 5V from a USB port. This is a boon for getting rid of DC jacks with various voltage and current ratings. It also helps prevent accidents where folks plug in a 12V power supply into a 5V port just because the plug is the same size. With classic USB power delivery, the client device communicates over the CC pins to the upstream computer or power plug to request any of the standard voltages: 5V, 9V, 12V (optional), 15V, or 20V and from 1A up to 5A. With software negotiation, the sink can figure out what power supply voltages are available then accept or reject to get the best power supply efficiency and performance. As we see adoption across many industries to use standard USB C, the power needs have also been expanded! As of USB PD v3.1 there is now Extended Power Range (https://www.usb.org/usb-charger-pd) which adds "three new fixed voltages: 28V (above 100W), 36V (above 140W) and 48V (above 180W)" for charging bigger devices like laptops or electric scooters. Plus a "new adjustable voltage mode enabling a range from 15V to one of three maximum voltages (28V, 36V, or 48V) depending on the available power allowing the device being powered to request specific voltages to a 100 mV resolution." That first quote is pretty clear: we now just have bigger voltages available so we can keep under the 5A current limit that fixes how much current the contacts themselves can handle with standard USB C ports/cables. The second is interesting because it implies we can now select voltages that are outside the standard issue. Now AVS only allows adjustment over 15V, probably this was a compromise since there's big jumps between 28/36/48V. There's also a separate variable-voltage specification called Programmable Power Supply (https://hackaday.com/2025/03/24/pps-is-the-hottest-usb-c-feature-you-didnt-know-about/) a.k.a PPS a.ka. "Fast Charge" (https://www.usb.org/node/585) which allows finer resolution from 3.3V up to 21V - or whatever is the max voltage on the power adapter - in 20mV voltage steps and 50mA current steps. Popularized by tablet/phone maker Samsung but now is appearing on other devices, it recognizes that often times charging speed is limited by the thermal dissipation capabilities of the charging circuitry. That is to say, even with buck converters, if they use tiny SMT parts there's still an 'optimal' voltage and current level that will give the best efficiency and thus charge rate. Just like not all voltages are always supported by USB PD power supplies, PPS support is not required so check the side of the adapter or the manual, to see if it mentions PPS and the voltage/current range. For PPS support, you need to use the AP33772S (https://www.digikey.com/short/59d9mbvm) because there's fine tuning required. But if you just want 'every day' AVS/PD support, where you can select the voltage and current required, the AP33771C (https://www.digikey.com/short/022nd0fp) is much simpler. Instead of having a full I2C setup and configuration, two resistors are queried on power up and used to auto-negotiate. The onboard LED can provide some basic feedback on whether negotiation succeeded. According to the AP33772S datasheet, there is a variant of the chip, AP33772SDKZ-13-FA02 (https://www.digikey.com/en/products/detail/diodes-incorporated/AP33772SDKZ-13-FA02/27346457) that supports having VSEL resistor for initial voltage configuration - that part is available for special order only. If you want a simple, low-cost way to add USB Type C power delivery with extended voltage support and PPS capabilities, the the AP33772S (https://www.digikey.com/short/59d9mbvm) and AP33771C (https://www.digikey.com/short/022nd0fp) are easy ways to make customizable or stand-alone power supplies easy. Now there's no excuse to not convert your next design to run on USB and ditch that confusing DC power plug for good! Whichever one you choose, they're both in stock right now at DigiKey for immediate shipment. There's even eval boards (https://www.digikey.com/en/product-highlight/d/diodes/ap3377-usb-sink-controllers) to get your design kick-started fast. Order today and you'll have fresh chips in hand by tomorrow to make your power delivery dreams come true.

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