LTC3351 without Vin

Hi there,

I'm working with the DC2464A-B (with the LTC3351) demo board and Linduino DC2026.

It's working fine: with the PC GUI V1.2.9.0 I can access to all registers and they are updated continuously with the "AutoUpdateEnabled" button.

The problem comes when I unplug the power, I mean I unplug the Vin on the DC2464A-B; THEN the PC GUI is freeze and stop to update!!!!!

I have done some test:

->With Vin=25v:

On LTC3351: INTVCC=4.7V;  Vout=25V   ; vcc2p5=2,5V

On DC2026: Rx(D4) and Tx (D5) blinking continuously: On 0.3S, OFF 0.7S approximately.

On SMBus: ACK from the Slave device. (Verified with a sniffer)

On PC GUI: values updated constantly.

->With Vin unplugged:

On LTC3351: INTVCC=4.7V;  Vout=18.06V (boost working)  ; vcc2p5=2,5V

On DC2026: Rx(D4) and Tx (D5) blinking continuously: On 0.3S, OFF 0.7S approximately.

On SMBus: ACK from the Slave device. (Verified with a sniffer)

On PC GUI: values freezed!!!!!

I have sniffed the SMBus communication with a sniffer and apparently there is no difference, I can see the ACK bit in both cases. If you want I can send you some images.

Seems that without Vin the PC GUI is freeze; NEVERTHELESS the LTC3351 SMBus communications are working.

MY QUESTION IS:

Can you assert that the LTC3351 SMBus communications will work meanwhile its boost is working, and Vin is unplug?

Thanks

Parents Reply Children
  • 0
    •  Analog Employees 
    on Jul 8, 2021 5:24 PM in reply to galo

    No, The default is with most of the ADC channels disabled in backup mode. I was just making sure they were turned on. I don't recall seeing this problem before so I was just thinking of what could cause this. 

    The time the ADC are sampled can be changed for charge mode or backup mode. What is the sample time for backup mode set to?

    This shouldn't matter but what is JP1 set to?

  • Hi Marty,

    I have done several test:

    With all AD channels on. With only the Vin AD chanel. With sample time to 40mS, with sample time to 400mS, restoring all the sheet to "default settings".

    With an old DC2464A-B updated manually (Vin range, Vout, L...); and with an absolutely new DC2464A-B. 

    ALWAYS with the same results. The PC GUI "SEEMS" freeze.

    As I told you the I2C communications seems work even without Vin. Before to design my schematic I need to assert that the LTC3351 will answer the I2C commands even without Vin. 

    Attach a GUI and I2C screenshoot.

    thanks

  • 0
    •  Analog Employees 
    on Jul 9, 2021 12:44 PM in reply to galo

    Hi, The attached screen shot shows all the ADC enabled in charge mode and disabled in backup mode. When VIN is lost all the ADCs will be disabled. Please select the desired ADCs to turn on in the backup column.

  • Hi Marty.

    Fixed. you are absolutely right. With all the AD chanels ON in backup mode, the PC GUI works without problems.

    Again, thanks a lot. Bravo for you.