BQ34Z100: LEDs not working when LED_ON bit is clear

Bhavil Nagar

    Are you using an EVM or a self designed board? if it is a self designed board, can you upload the schematic?

I am using a self-designed board. I will send you the schematic over the DM.
I have also created a breadboard version by using figure 8.1 present in the BQ34Z100 datasheet.

Bhavil Nagar

    The push button shall be used to connect SW and VEN, not REGIN and VEN, your schematic is for External LEDs with I2C, what is the setting for LED/COMM Configration??

Hi Steven Yao
I have a separate LED connector board which I am connecting with the BQ34Z100. If you see the "LED Connector" Part in the schematic, the SW and VEN will be connected when the pushbutton is pressed. See the schematic of the LED board that I am using.

The Hex value I get under LED/COMM Configuration is 53. I am using 6 LEDs(EXT_LED0 and EXT_LED2 are set) and LED Mode_1 and LED Mode0 are set.

Bhavil Nagar

    Can you try with MAC command 0x0030, 0x0031 to turn on and turn off the LED manually see if it works? i.e., send 0x0030 to 0x00, send 0x0031 to 0x00

Hi Steven Yao

No, the LEDs are still off after sending the commands. Please see a screenshot from the BQStudio below to verify if I am doing it correctly.

Bhavil Nagar

    The bytes sent should be reversed in the sequence of 30 00

Thanks Steven,

The LEDs are working with the MAC Command. It replicates 100% SOC.

Hi Steven Yao

Please find the oscilloscope readings across VEN and GND



Image 1- When the button is not pressed. I have tried to see the readings on VEN and REGIN pin before on the oscilloscope, but have never observed such erratic readings.



Image 2- When the button is pressed. The max reading is about 2.32/2.4V which explains why the LED is not working on button press. The REGOUT is showing 2.5 volts, the voltage drop seems to be across the wires connecting my LED board and the bq34z100 or the switch.

I have another board. I will connect that and see if the same issue persists, because I have created a breadboard setup, and reading the voltages on the same shows me that the VEN pin gets 2.54V but the LEDs does not light up.

Hi Steven Yao

I tested my setup on another board that I have which has Identical settings. I even used the same LED Board with this one. Image 1- When the button is not pressed VEN at 600mV

Image 2 - When the button is pressed. VEN is at 2.5V

Hi Steven,

The voltage stays up at 2.5 as long as I hold the button.

I do not have the EVM. I want to order the EVM but, I guess the payment gateway for my country is disabled for some reason and will resume after 31 August.

Bhavil Nagar

    I mean how long do you hold the button down, could it be approximate 1s or so.

    When you press down the push button, there should be clock pulses observed on P2, P1 should also flips at the same time. Could you see such pulses?

Hi Steven Yao,

I usually try to hold the button for 1-2 seconds. both P1 and P2 are set at 2.5V regardless of whether the button is pressed or not.

Bhavil Nagar

    You should be able to observe pulse train when you press down the button, can you?

    Otherwise, you may need to check the signal from the source end by probing directly at P2 and P1 pin of bq34z100

Bhavil Nagar

    Please also check LED Hold Time is set too short to observe the LED being lit on, you can set it longer so that the LED lit on can be observed.

Steven Yao

No, There is no Pulse in P1 and P2. They stay constant at 2.5V regardless of me pressing/holding the button or not. I have increased the LED Hold Time to 10 from 4. Still no LEDs. I am checking the signal on Pin1 and 3 for P2 and P1 respectively on the BQ34z100.

Another thing that I have noticed is that the Voltage at my LED1...6 pins is equal to whatever the voltage is at my REGIN pin.

Hi Steven Yao

Do you have any updates?

Hi Steven Yao

At the moment We are using a 1S system and hence not using the diode. The max voltage given to REGIN pin is 4.2V

Bhavil Nagar

    The schematic you sent to me is not for single LED usage, can you send the schematic you are using for single cell application?

Hi Steven Yao,

I am sending you one over the DM. Please check it

Hi Steven Yao

Thanks I'll have a look into it,

I just have another doubt. Is there a voltage difference at the Data and Clock pin of SN74 created by bq34z100 when the LED_ON bit is set vs when it is clear.

Because I can have the LEDs working properly, when  the LED_ON is high but not when it is LOW. Can this one register bit bypass the 75% VCC requirement?

Bhavil Nagar

    This could be due the High level on data and clock being marginal, have you tried by lowering down the VREGIN see if LED can be lit on by pressing down the button?

Hi Steven Yao

Yes, I have tried different voltages ranging from 2.8V to 4.2 V. I now think that this might have something to do with the PCB/Schematic. I will be working on a new schematic taking reference from the EVM as opposed to the schematics in the bq34z100 datasheet. Would you be able to help me doing a review of the same some time later?

Thank you for your time and support on this one.

Thanks Steven Yao

I'll also get an EVM for comparision

Hi Steven Yao,

I just got the EVM. When I first gave power to the EVM all the 10 LEDs lit up. At this point, the board had the same firmware in which it was shipped.

After that I just changed the LED_Comm Configuration to "9b" as shown in the pic below, and the LEDs stayed on and displayed the actual SOC which it calculated. At this point the SOC shown on the app was 5%

But when I change the LED_Comm Configuration to "93" and clear the "LED_ON" bit, the LEDs can not be controlled using the button on the board.

Can you check if the jumpers are placed correctly?

Bhavil Nagar

    The jumper on J1 should be removed, others shall be OK, what is voltage on REGIN?

Steven Yao,

I have removed the J1 Jumper, but still the same thing. REGIN is at 4V at the moment. Yesterday I tried at 3.6V REGIN

Do I need to change any other register or settings as the only thing I have changed in the EVM is the LED_Comm Configuration?

Hi Steven Yao

My CLK Signal is continuously on 2.5V or near about when the "LED_ON" bit is clear. I have tried holding the button for 1/2/3/4 seconds with no difference in my output.

I will try to import your gg file and will amp up my BAT+ to 14.8 volts and tell you if there is any difference.

Steven Yao said:

When press down the button, the first series pulse string on the CLK input of SN74HC164 is a 5-pulse string

Just to confirm you are measuring this with respect to BAT-?

Bhavil Nagar

    Yes, all above signals are measured with respect to BAT-

Thanks, Steven Yao
Interestingly, the LEDs started working after I imported the Data Flash settings you sent and the Firmware file. Guess I set some of the registers the wrong way. Thanks for your time. I appreciate it.

One last thing, the app shows that the voltage of my battery is 16832 mV as opposed to the 14.8Vs I am providing. I read the documentation a month or so ago, but I suppose there is a multiplier register that I have to set, which will sort this out for me?

Edit: The voltage on REGIN is 3.7Vs

Steven Yao

Thank you so much for all your time.

Thanks, Steven Yao,

maybe yeah, I will try this with my other boards as well and see if anything changes.