I am trying to design a charging circuit which support QuickCharge but also I want to add USB-UART bridge to communicate with on board MCU. How can I establish voltage level safe communication through UART bridge while VBus level is controlled by fast charge IC? What I mean, VBus would be get higher as 20V. Generally found USB-UART bridges are just handling 5V max. Lets look CP2102. This IC has actually self-powered configuration through Vdd but that still needs to be connected to VBus with threshold 5V. There should be some simple solution I could not think.
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\$\begingroup\$ The simple solution may very well be to not mix fast charger capability with a USB comms capability. It would seem that your not being sure of how to handle the situation suggests that you should leave well enough alone. \$\endgroup\$– Michael KarasNov 7, 2018 at 3:26
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1\$\begingroup\$ Would a 5-V voltage regulator work for you? What kind of reference designs are available from QC control ICs manufacturers to guide you? \$\endgroup\$– Ale..chenskiNov 7, 2018 at 6:48
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\$\begingroup\$ only 3.3V is needed for the UART beridge, perhaps there's an LDO regulator that can handle 20V in \$\endgroup\$– Jasen Слава УкраїніNov 7, 2018 at 7:44
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\$\begingroup\$ what sort of USB-UART bridge is capable of also negotiating fast charge? \$\endgroup\$– Jasen Слава УкраїніNov 7, 2018 at 7:46
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1\$\begingroup\$ @Jasen, USB-UART bridges don't negotiate QuickCharge, true, but power circuits around it can. However, there seems to be one little problem with QC: it uses DC levels on USB data lines to negotiate fast charge, and gets disabled if you need to use USB for data transfer. I have found no indication that QC and data sync can work simultaneously. I would be glad to hear otherwise. \$\endgroup\$– Ale..chenskiNov 8, 2018 at 19:19
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2 Answers
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You should use a USB 3 PD controller (sink role). These devices pass the D+ and D- while implementing the power levels negotiations with the host.
answered Apr 6, 2022 at 19:35
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power the UART from the battery.
answered Nov 7, 2018 at 7:46
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\$\begingroup\$ Sorry my mistake; deleted the automatic remark. \$\endgroup\$ Nov 7, 2018 at 9:23
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\$\begingroup\$ Would it be a problem to connect all data lines then? USB-UART Bridge would be CP2102 and quick charge IC is CHY103D. \$\endgroup\$– meakceyNov 7, 2018 at 9:45
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1\$\begingroup\$ CHY103 goes inside the charger, what do you have inside the device to call for fast charge? \$\endgroup\$ Nov 7, 2018 at 9:52
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\$\begingroup\$ CHY103 makes it fast charger by communicating with the connected device through data lines. Voltage feedback network is controlled by it. \$\endgroup\$– meakceyNov 7, 2018 at 10:14