SPV1050 Battery charging in case of loading

[PPats.1]

Hello there,

I am planning to design an environmental IoT sensor node and i would like to incorporate the SPV1050 IC since it covers my project needs.

I did extensive reading of the datasheet and there are some things I would like to get cleared:

1. does the dc-dc converter have a dedicated bus for BATT charging?

2. if no (probably that's the case as I understood) what happens if there is a load connected to the store pin like an mcu, under voltage is triggered and pass element get open, how the battery is going to charge. what happens if voltage at the pin never manages to trigger over-voltage threshold for the pass transistor to close and charge the battery. That could happen because of the load consuming Cstore.

Is there something I am missing about the battery charging system.

Kind Regards

Patsaoglou Pantelis, GR

[Peter BENSCH]

1: no

2: The undervoltage detection is carried out via the UVP pin, which in turn is connected to the STORE pin via a voltage divider.

If a load is currently being charged, the energy at the input should actually be high enough to supply the load and thus maintain the charge of the battery. However, if the load is exceptionally greater, the battery is slowly discharged, which then triggers the UVP through the still closed pass transistor. This opens the pass transistor, which causes the voltage at STORE to rise. Once this voltage has reached the overvoltage limit, the pass transistor closes again and can then charge the battery with the stored energy from Cstore. Please don't forget: the load is connected to the battery, not to STORE.

Take a look at Fig 3 and the text above it in the data sheet, which may also help you with your design.

Does it answer your questions?

Regards
/Peter

[PPats.1]

Good morning!

Appreciate the fast response! Datasheet states page 5 STORE pin ''Tank capacitor connection pin. Application load, if any, should be connected to STORE or LDOs pins''. That's why I got confused!?

So as I described the case above, ldos power up only if voltage parameters from battery or dc to dc are covered as specified in the step up power sequence details.

Kind regards

Patsaoglou Pantelis, GR

[Peter BENSCH]

Interesting catch! This addition was not yet included in the data sheet versions prior to rev 8.

If I had a board with the SPV1050, I'd check it out. If someone from our Analog Division jumps in, please feel free to correct my statement.

Regards
/Peter

[PPats.1]

Thanks.

Looking forward for the update.

Few last questions I am curious about:

1) Is the 3v3 ldo performance reasonable when there is an Wireless application? Are there any tests made. I started all this discussion because I don't feel LDO can handle transmits with more that 200ma bursts. That's why I am searching for the unregulated topology, to be save currentwise:grinning_face:. Let me know on that.

2)So I wait for clearance on the unregulated topology? Am I save from the assumption I made in the first post? Let me know of any details!

Thanks again 

Best regards

Patsaoglou P.

[Peter BENSCH]

1. The SPV1050 was launched in 2013, at a time when such wireless applications were still somewhat in their nappies. In this respect, nobody has been able to measure the performance of the LDO for such applications. However, I could imagine that it might be possible to buffer with sufficiently large capacitors for burst transfers.

2. I don't know what you mean by "unregulated topology". Surely the battery voltage is regulated and charging is interrupted once EOC is reached?

[PPats.1]

I meant not using LDO regulation. Straight power from battery power while having the uvp, eoc functionality.

Btw, i haven't come across any other ics for these applications by st(excepting the SPV lineup)

Regards

Patsaoglou P.

[PPats.1]

Hello,

Is it possible to clear out the configuration when load is connected to the cStore pin as stated to the datasheet by forwarding it to the analog department. Is it safe from issues as I stated at the top of the thread? I would like to know that, in order to opt the best configuration to continue the project.

Thanks again!

Best regards,

Patsaoglou Pantelis, GR