AP9214L-AN doesn't turn on - Page 1
Forum section: electronics / projects

author: barvit
author_rank: Newbie
timestamp: November 22, 2022, 02:35:07 pm
content: Hello,I produce some gadget wich is powered by lithium polymer battery. The battery is very small. It is only 8 mA. The charging current is 15 mA. I use AP9214L-AN (Diodes) as a protection for the battery. The power circuit schema is attached.If the battery voltage is less than 3.2V AP9214L-AN turns off the battery and should recover normal status from overdischarge status by charging the battery through the charger.I have 5% warranty return. AP9214L-AN doesn't turn on by charging the battery through the charger.AP9214L-AN has the technical capability (it is not available for consumers) to turn on by shotting S1 and S2 pins. After I shot S1S2 the gadget works properly without any trouble (I discharge and charge it repeatedly).So the problem is that I can't still catch the issue on my table after a lot of testings.Need advice.What could it be?Could it be fixed by changing R1, R4, C1?

author: brumbarchris
author_rank: Regular Contributor
timestamp: November 22, 2022, 03:52:54 pm
content: The AP9214L still draws some microamps from the battery, even wen the load is disconnected. It could be that on those 5% samples the following scenario occurs:1. Battery voltage falls below 3.2v, the AP9214L cuts off hte load2. The overall device is not being immediately charged, so battery continues to be drained by the power down mmode quiescent current of the AP9214L3. The battery drops below 1.5V, which is the minimum operating voltage of the AP9214L4. Subsequent plugging of the charger results in the necessity of going through the cold start procedure of the AP9214L, which imvolves te.porarily shorting the S1 and S2 pins.Could this be the case?

author: barvit
author_rank: Newbie
timestamp: November 22, 2022, 10:33:41 pm
content: brumbarchris thank you for your advise.It was the first thing I thought.But now it seems that it was not a reason.First, testing returned gadgets I learned that the battery residual Voltage in the vast majority of cases was about 3.2V (Voltage when OverDischarge Status turns on). Very often it was even 3.45V-3.50V. Ussualy a battery without a load shows Voltage higher than it was with a load before.Second, AP9214L has integrated option "0V Battery Charge". So it should proceed with "0V" batteries automatically. I checked that many times. It worked fine.It looks like when you make mistake calculating pull up risistors on some microcontroller's pin. And that pin finally has voltage ~ 1.6V. It is neither a stable logical "0" nor a stable logical "1". And even a pulse power adapter (let's say Mac computer) by near may affect on that pin.So the problem is that I can not catch the issue when it begins. If I can I could find the way out by changing resistors step by step in one direction or another.

author: smerrett79
author_rank: Contributor
timestamp: November 23, 2022, 11:33:05 am
content: Funny you should mention this - I've had some prototype boards "die" with this exact problem. There is a safety feature in the charging IC that we're using that was initially also under suspicion but because the symptoms are exactly as you described, I'm now convinced it's the AP9214L.I may try and vary resistor and capacitor values. I have 330 ohms and 100nf on the input and 2.7k ohms on the feedback pin. I also have 10uF across the +P / -P "output" terminals to the wider system.

author: barvit
author_rank: Newbie
timestamp: November 23, 2022, 04:25:26 pm
content: smerrett79, excellent news for me! It would be great if you could try different resistors.It seems there are two options for the current issue1. AP9214L doesn't work at all.We can try to reduce R1. Allowed range is 330-470 Ohms. Nevertheless even Diodes itself use R1=220 Ohms in their datasheet (please take a look at attached screenshot). So we can try 220 Ohms and less. As I understand the bottom value "330" is important only if the battery or charger is connected reversely.2. AP9214L works, but doesn't feel a charger connected.We can try to change R2 (R4) both directions (let's say 300 Ohms and 4kOhms).Let me know what are your prototype board's- charging current- battery capacity

author: smerrett79
author_rank: Contributor
timestamp: December 22, 2022, 01:17:47 pm
content: Hi, apologies for the delayed response. I have been discussing this issue with Diodes Inc application engineer. They asked me to take several traces of different signals during different plug-in-USB etc events. They have made some helpful diagnostic suggestions and we have been iterating over the last few weeks.The main suspicion is that we are in a chicken and egg situation whereby the initial "safe/shipping" mode of the AP9214 means the S1-S2 FET is disconnected, so no potential is seen across BAT+ and S2. Applying charge voltage across BAT+ and S2 (our/your system GND/reference) should make it connect S1-S2 and both charge and discharge should start to work. However, we also have chargers which implement UVLO protection on their outputs. This means in your case that (from a quick scan of the MCP73832 datasheet) a 6uA current is sourced from VBAT. It then tests the voltage at VBAT (connected to BAT+) to see if it is within the VREG+100mV range. My charging IC does something similar to test if a cell is present. If S2 (GND) is not connected to S1 (BAT-), then BAT+ is possibly floating with respect to our system GND reference potentials, so our charging ICs never apply a voltage across BAT+ and S2 to turn the S1-S2 FET on. I'm totally guessing on your side because I haven't got to know your charging IC but ours is looking like this is the issue.I have asked for a proposed safe way to ensure the AP9214 does not fail to trigger charging IC cell detection, because it is affecting at least two different charging ICs from different manufacturers. Please forgive if I don't share my part number because of supply chain sensitivity but I can tell you that I'm charging at under 300 mA and have 4.2V as my cutoff voltage.So far the only apparent alternative to supplying charging voltage across BAT+ and S2 as the AP9214L activation method is to manually short S1-S2. I have provisionally added a momentary switch to my next design revision but I am awaiting Diodes Inc feedback on whether they endorse this as a safe method (and whether there is a method that does not require the user to activate it from inside the enclosure). I hope that gives you some ideas to continue diagnosing your own circuit. I'll try and update when I have more. I have also turned notifications on so hopefully will see if / when you reply.

author: barvit
author_rank: Newbie
timestamp: December 22, 2022, 08:31:05 pm
content: Hi,smerrett79, thank you for your detailed research.1. I met some communicative consumer. After he faced the issue I sent him a replacement unit and ask to keep me updated how it goes step by step. Now I know exactly the issue appeares even if the battery is fully charged and a charger has not been plugged before.According to AP9214L datasheet:"For power-down mode, when first connecting AP9214L system board to the battery, it is necessary to use charger or to short P- to the battery negative polarity."So now it looks like AP9214L periodically loose connection and then see the battery as new connected. And requires the first "activation".R1 is already maximum of the recomended range (470 Ohm). I increased C1 to improve rc filter.Hope it will help and the cunsumer will be still so kind to give me some feedback. He should get the corrected unit in few days.2. About your circuit. As far as you charge at 300 mA our issues may be not the same.My gadget consists of two units. They have two different lipo batteries on bord.Unit 1. Capacity = 8 mA. Charging currrent = 15 mA. Vreg = 4.2 VUnit 2. Capacity = 160 mA. Charging current = 160 mA. Vreg = 4.2 VI faced the issue only with Unit 1 (8 mA). Never with Unit 2 (160 mA). But pay attention my R1 = 470 Ohm.