BQ78350-R1: IN_SYSTEM_SLEEP required for device sleep

Hi JP,

The device should be able to go into sleep without activating IN_SYSTEM_SLEEP. Are all of the conditions satisfied for the device to go into sleep (no communication on SMBUS, DA_Config[SLEEP] = 1, Current() < Sleep Current, Voltage Time > 0 , etc.?

Matt

Hi Matt,
As far as I can tell all other conditions are satisfied. According to the technical document, even IN_SYSTEM_SLEEP needs all the regular sleep conditions met before the device goes to sleep. And in in system sleep it goes to sleep when SMBUS is removed. When I turn IN_SYSTEM_SLEEP off, remove ground from the PRES pin, and remove the SMBUS, the system does not go to sleep (PWRM stays high).

JP,

Can you check the GaugeConfiguration[PWRMSleep] setting? This is probably not the issue since it is 0 by default.
Also, can you let me know your settings for the Sleep Subclass Data Flash parameters (Sleep Current, Voltage Time, Current Time)? Are the SMB low timeout bits (BLT1:0) set to a non-zero value? Are there pullups holding the SMBUS high?
Are you using the ManufacturerAccess() Sleep mode command?

Sorry for all of the questions. The device should be able to go into sleep without using IN_SYSTEM_SLEEP.

Matt

Hi Matt,
No worries. I appreciate the questions. It helps solve the issue/ narrow down potentials.

PWRMSleep= 0
Sleep Current = 1mA
BusTimeout = 1s
Voltage Time = 255s
Current Time = 255s
There are no pullups on the SMBus lines
I'm not using the MAC sleep command. I'm disconnecting the Bus and removing gnd from the PRES pin to get it to go into sleep mode (or try at least).

Thanks,

JP

Hi JP,
Matt is on vacation this week so we apologize for the delay in responding to your latest information. He will get back to you next week.

Hi JP,

It looks like everything is okay with your settings and I cannot see anything that would prevent the device from entering Sleep. Are you still working to debug this issue?

Thanks,
Matt

Hi Matt,
Yes, this issue is still on the "really important" list. Is there anything on the schematics that you see that may cause this? I've tried everything and I just can't seem to get it to sleep.

Thanks Matt 

Hi JP,

I looked through the schematic and I don't see any issues. Can you measure the PRES pin and the SMBUS pins to make sure they are being pulled to the correct voltages? Is the device in RELAX state when these signals are removed? I believe SLEEP mode is entered from RELAX. You can check the REST bit to see if it is in this state before disconnecting the SMBus.

Have you checked the PFStatus, PFAlert, and SafetyAlert bits to make sure no faults were detected preventing sleep? Are you physically removing a battery pack for this check?

Thanks,
Matt

Hi Matt,
Right now we have this setup:
1) When the cable that connects to the EV2400 is plugged in the pres pin is automatically tied to ground and is low and the SMBUS is pulled high and has activity.
2) When I unplug the cable and disconnect from the EV2400 the pres pin is low but pulses to 2.5V every 250mS and both SMBD and SMBC are low with no activity.
3) The REST bit (the one that is part of Gauging Status) is NOT set before I unplug the SMBUS.
4) While it is plugged in no status or alert bits are being set.
5) Right now for this setup I have my power supply connected to the battery terminals and a resistor ladder representing the cells. For this check I am disconnecting everything from the output pins which are: SMBUS pins, a pin that is tied directly to the battery to check voltage, the pres pin which is floating once the connection is removed, and pack + and pack-.

Hi JP,

This is still very puzzling. I talked to one of my colleagues about this issue and there should not be anything preventing the device from going into SLEEP if IN_SYSTEM_SLEEP is working okay. One thing to investigate is whether there is any noise on your PRES pin that is causing a false reading. Is it possible there are any leakage currents that may be affecting the PRES voltage or current readings?

Thanks,
Matt

Hi Matt, What I'm seeing on the PRES pin when I disconnect is a 2.5V pulse every 250mS. If that is normal then the signal waveform looks fine to me.

Hi JP,

I assume this issue is still ongoing? I'm sorry we haven't been able to find the cause of it yet. Are there any other leakage currents in your system that might trigger an exit of the Sleep condition? Do your status bits show that the device is charging or discharging when you try to enter sleep mode (I'm asking because you indicated the REST bit is not set).

How are you determining whether the device is in Sleep mode?

Let me know the latest status and I can investigate further from my end.

Thanks,
Matt

Hi Matt,
I guess my main issue is that I'm able to sleep while in system sleep is activated. I can see PWRM change state and then after a minute it shuts down based on auto ship time. When I turn of in system sleep none of those things happen. Am I correct in saying that the PRES pin is the only difference between in system sleep and regular sleep? Because in order to go to sleep while in system sleep, it says that you have to satisfy the requirements for sleep mode. Based on my description, is the PRES pin behaving normally?

Hi Matt,
Please look at my post: e2e.ti.com/.../724367 and tell me if there is a possibility that these two issues can be related.

Thanks,
JP

Hi JP,

I think there is definitely a possibility that these two issue are related. I'll start looking into the questions on the 2nd post now.

Matt

My only issue is that the battery isn't loaded at the time so there is no high current on that path and pres on the scope seems to be fine.

JP,

That's really great to hear. If you discover at some point what what causing the issue, please let us know. I'm sure we can learn from it.

thanks!
Matt