BQ25750EVM: Switch time from VIN to Battery for VSYS Power

Looking at the Studio screenshot, it says not charging and not power good. Just confirming that is because there is no VIN when this capture was taken ?

In our experiments, we have noticed that the ACDRV takes 3ms while the VSYS takes less than 1ms to switch after handover. The 1.3s number does not seem right.

Hello Expert.

When VIN is disconnected and switching from VOUT/VBAT to VSYS through BAT_DRV there is a delay time of approximately 1.3 seconds.

When using the AUTO REV_function, a delay of approximately 3ms was confirmed.

We would like to use the BAT_DRV function.

I would like to know how to switch without delay using BAT_DRV.

VIN: 9~36VDC
VBAT: 28VDC

Hi,

The AUTO_REV function is for the reverse mode operation of the device. It does not control the power path transfer. The ACDRV and BATDRV timings should be very similar and waveforms should be opposite. In our tests, we have seen power path transfer happen in a few miliseconds. I believe maybe there is a problem with the setup or we are missing something here if you see 1.3s. Could you please plot IBAT, ACDRV, VSYS and BATDRV on the scope for both VAC--> VBAT and VBAT--> VAC transfer and share with us ? For the same VIN and VOUT voltages. Furthermore, do you have a load ?

Hi,
I am attaching the waveform you requested.
It operates normally at 0A, but does not operate at over 0.5A.

# Could you please give me the demo board you have?

CH1(YELLOW):VAC
CH2(RED):ACDRV
CH3(BLUE): BATDRV
CH4(GREEN): VSYS

<0A LOAD>

<0.5A LOAD>

* Created: Thu Mar 07 10:15:28 KST 2024
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* BQZ Container: Charger_1_00-bq25750.bqz
*
Charge Voltage Limit	00	10
Charge Current Limit	02	140
Input Current DPM Limit	06	640
Input Voltage DPM Limit	08	348
Reverse Mode Input Current Limit	0A	640
Reverse Mode System Voltage Limit	0C	1C20
Precharge Current Limit	10	50
Termination Current Limit	12	A0
Precharge and Termination Control	14	0F
Timer Control	15	4D
Three-Stage Charge Control	16	00
Charger Control	17	C9
Pin Control	18	C0
Power Path and Reverse Mode Control	19	00
MPPT Control	1A	20
TS Charging Threshold Control	1B	96
TS Charging Region Behavior Control	1C	57
TS Reverse Mode Threshold Control	1D	40
Reverse Undervoltage Control	1E	00
VAC Max Power Point Detected	1F	00
Charger Status 1	21	06
Charger Status 2	22	80
Charger Status 3	23	02
Fault Status	24	00
Charger Flag 1	25	00
Charger Flag 2	26	00
Fault Flag	27	00
Charger Mask 1	28	00
Charger Mask 2	29	00
Fault Mask	2A	00
ADC Control	2B	60
ADC Channel Control	2C	0A
IAC ADC - Use Field View	2D	00
IBAT ADC - Use Field View	2F	00
VAC ADC	31	00
VBAT ADC	33	00
VSYS ADC	35	00
TS ADC	37	00
VFB ADC	39	00
Gate Driver Strength Control	3B	00
Gate Driver Dead Time Control	3C	00
Part Information	3D	02
GM Adjust	61	30
Reverse Mode Battery Discharge Current	62	02

Looking at your results, I must ask what components are you using ? I feel that they might not be sufficient to handle power path transfer. Are you using the same components as the datasheet available on our website or do you hve your own components on your own board ? Power path transfer is dependent heavily on the SOA of the MOSFETs used and also the supporting inductor, capacitor etc. Please let me know your system specfications including switching frequency as well. Please refer to this link for our datasheet to see the parameters and also order a demo board if needed.

www.ti.com/.../BQ25750

Hi Sung, are you using the default BQ25750 EVM from TI ? That is the same one I am using. My ACFETs and BATFETs are AONS6276.

hi,
We did not change any part of the demo board.
I would like to request a waveform that switches.

After completing charging from VAC to VBAT, take a picture of the waveform output to VSYS through BATDRV_FET when VAC is turned off.

Please provide BQ-Studio registration file.

VAC_MIN: 9VDC
VAC_MAX: 36VDC
VSYS: 5A
VBAT:LI-ION_7S1P

Hi Sung, I will try to recreate the same condition that you have in the lab and get back to you with the waveform next week.

hi.
When can I receive the requested waveform?

Hi Yun,

Thank you for being patient. I am very busy with a lot of work but have procured a board to perform the desired tests. I will try to get you the waveform before the end of this week. Sorry for the delay.

Hi Yun, please see attached some basic waveforms. Before I proceed with your specific waveforms, I want to confirm, do you want 5A load or 0.5A load. Earlier you mentioned 0.5A and later 5A so I just wanted to check and make sure.

HI. Gupta,

I requested VSYS_5A load.

If you look at the uploaded waveform, you can see that after VIN is turned off, VSYS is also turned off.
It has not entered BAT mode.
I would like to see the voltage output across the BAT DRV_FET after VIN is turned off.

Please take a picture of the following waveform.

CH 1 : VIN_28VDC

CH 2 : VSYS

CH3 :  VOUT(battery)_24VDC

CH4 : VSYS_Current_5A

Hi, I will get back to you with that waveform this week.

hi,
Thanks for your reply.
Please provide the "bqStudio Registers" file you tested.

I will get back to you on this.

Hi, we are using some experimental settings to achieve the results I shared with you. These settings are not final yet and cannot be modified by the user. These settings are set at the factory.