0
\$\begingroup\$

I want to use MCP73833 as a charger IC with the ability to route STAT1, STAT2, PG to RaspberryPi GPIO. Those are open-drain outputs and should be pull-up, according to datasheet. The datasheet also says that PG can't be pull-up to the MCP73833's output but only to the input due to IC's internal schematic.

My question: how should the pins be pulled-up correctly keeping in mind that GPIO has 3.3V level and MCP73833's input is around 5V?

RESOLUTION

Below is my final schematic. Thanks to Maple. enter image description here

\$\endgroup\$
  • \$\begingroup\$ Data sheet link? \$\endgroup\$ – Andy aka Jun 22 '18 at 17:59
  • \$\begingroup\$ @hanni76 I deleted my answer since it had some mistakes. Sorry. \$\endgroup\$ – mguima Jun 22 '18 at 20:20
  • \$\begingroup\$ @Andyaka Here is the datasheet ww1.microchip.com/downloads/en/DeviceDoc/22005a.pdf \$\endgroup\$ – hanni76 Jun 22 '18 at 20:45
  • \$\begingroup\$ Looks good, should work. Thank you for updating with your final schematics, might help somebody else one day \$\endgroup\$ – Maple Jun 25 '18 at 19:45
0
\$\begingroup\$

Simply add 4.7~10k pull-ups to 3.3V for STAT pins and use voltage divider on PG pin, with 1.2k resistor to 5V and 2k resistor to ground.

UPDATE

Your comment made me think of what is really going on inside that chip with PG pin. I still believe that voltage divider should work, but in case it will disrupt the functioning of the MCP somehow, you can leave the pull-up resistor only and add a buffer between output and RPi, something like NL17SH17

UPDATE 2

MOSFET or JFET can be used instead of buffer. Here are some examples, inverting and non-inverting.

enter image description here

\$\endgroup\$
  • \$\begingroup\$ Thank you. That makes sense. Could you explain, please, why PG pin can be only used with voltage divider? What is different with it ? \$\endgroup\$ – hanni76 Jun 22 '18 at 20:43
  • \$\begingroup\$ Unfortunately the internal schematics does not show details, so I would simply go with datasheet explanation and pull-up to 5V as they suggest (that's top part of voltage divider). It seems they are using it internally for other purposes too, the datasheet is talking about "pulsing PG to determine if battery is present" whatever that might be. Don't worry about it, just follow datasheet recommendation. \$\endgroup\$ – Maple Jun 22 '18 at 21:08
  • \$\begingroup\$ Try resistors first. If doesn't work then sure, MOSFET can be used. I'll update an answer. \$\endgroup\$ – Maple Jun 24 '18 at 11:19
  • \$\begingroup\$ I think a buffer is a better solution as it is a single component not needing extra parts. For example, TI's SN74LV1T34 is a tiny SOT23-5 IC. \$\endgroup\$ – hanni76 Jun 24 '18 at 18:38
  • \$\begingroup\$ It's funny, that is exactly the reason I suggested buffer in the first place. I hate having more components on PCB than absolutely necessary. \$\endgroup\$ – Maple Jun 24 '18 at 19:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.