0
\$\begingroup\$

I have designed a project that includes a TP4056 with DW01 protection ic and porwer sharing feature. Now I want to include a fuel gauge and the only one I have found is MAX17048 I have readed the MAX17048 datasheet ant it shows you should connect GND and CTG pins to GND but I have 2 different "grounds" one the BAT- pin and the other one is the "real" common GND.

TP4056 Circuit

I don't know which one should I use because if I use the BAT- then may be a problem when I interface it with the uC because ground isn't the same, but it I connect it to GND I don't know if it will measure the real battery level. Which one should I use and why (if possible)?

MAX 17048 application

Thanks in advance for your help!

PS: I'm sorry if my english is'nt good enough I have done my best.

\$\endgroup\$
2
  • \$\begingroup\$ The MAX17048's application circuit suggests you to where to connect already. The block named "PROTECTION" basically consists of DW01 and the back-to-back NMOSs. \$\endgroup\$ Jul 21, 2022 at 17:50
  • \$\begingroup\$ @RoharKiliç Thanks for your answer! I have seen the protection block but I dont really know which is the protection pin it refers because DW01 is connected to GND in the pin 2 and B- in the pin 6. If i connect it MAX17048 GND to DW01 pin 2 then I'm just shorting BAT- and system GND but if I connect MAX17048 to DW01 pin 6 then MAX17048 ground and system ground are not the same and It can cause problems when interfacing the uC. \$\endgroup\$
    – Emirikol
    Jul 21, 2022 at 18:11

1 Answer 1

0
\$\begingroup\$

but it I connect it to GND I don't know if it will measure the real battery level.

The real gnd is where you need and define 0V, which for logic is the MAX17048 and the uC logic interface.

The 5V connections +/- must be isolated from ground then the SoC measurements are differential on the battery -ve when connected to ground=0V.

If this uC is working during charging, and there is common mode RF noise from the charger 5Vin then a small RF cap may help from OUT- to GND.

The problem with connecting B- and OUT- is when drawing power OUT and charging at the same time, the charger is also sensing OUT power. If that power happens to be more than the cutoff current threshold (? 5% of CC) during CV mode at 4.2V then it may never cutoff and degrade the battery. So by adding a separate current sense resistor charging while using battery power can be used. So the I hope this is correct.

\$\endgroup\$
4
  • \$\begingroup\$ Thanks for your answer. So I must connect MAX GND to System GND isn't it? As far as I know B- and GND is the same unless DW01 disconnect it to avoid discharge right? \$\endgroup\$
    – Emirikol
    Jul 21, 2022 at 18:15
  • \$\begingroup\$ Yes but how are you intending to connect USB and uC with 5V for both circuits? \$\endgroup\$ Jul 21, 2022 at 18:33
  • \$\begingroup\$ What do you mean? I use a boost to get 5v from battery and i use USB power when it's charging. \$\endgroup\$
    – Emirikol
    Jul 21, 2022 at 18:39
  • \$\begingroup\$ I meant is your uC gnd also communicating to the same device with USB providing 5V \$\endgroup\$ Jul 21, 2022 at 18:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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