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LDC1612: Questions regarding LDC1612 behaviors

Takashi Onawa
Genius 13200 points
Part Number: LDC1612

Hi Team,

I got following two questions from my customer. Could you tell me how LDC1612 behaves in following case?

1. Address 0x18, STATUS, ERR_CHAN[15:14]

According to the datasheet, ERR_CHAN bits will be as follow when getting something error.
if Ch2 error occurs before Ch1 error  is cleared, what happens to the value of this Bits?

b00: Channel 0 is source of flag or error.
b01: Channel 1 is source of flag or error

2. Changing ADDR after power up

What will happen if I change the ADDR Logic(Like high to low) while the device is running and not during shutdown?

Regards,

Takashi Onawa

  • +1
    TI__Mastermind 18545 points

    Hello Takashi, 

    When a bit field in the STATUS register is set, the entire STATUS register content is held until read or until the DATAx_MSB register is read. If neither of these reads occur, then Ch2 error will not show on the ERR_CHAN bits. 

    Changing the ADDR pin during operation can cause unknown behavior. We can't guarantee any consistency in operation as the impact it will have on the device may be random. It is best to go into shutdown mode if you need to change the ADDR pin. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Genius 13200 points

    hi Beigel-san,

    Thanks for your prompt response on this.

    OK, I understood.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Genius 13200 points

    Hi Beigel-san,

    Sorry, I got one more question from the customer, regarding ADDR switching timing.

    They understood that there is a rink to switch the ADDR logic in active mode but how about in sleep mode? 

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 18545 points

    Hello Onawa-san, 

    If the ADDR pin is switched during sleep mode, there is still the chance for unexpected register behavior. If the pin is toggled, I would recommend either reading all registers to ensure they are still in the proper state, or soft resetting the device and reconfiguring it based on the customer needs. Either way, it is still better to go into shutdown mode to change this. 

    Is there a reason the customer needs to change the ADDR pin? A possible alternative is using an I2C Mux that can switch between the two devices. We have done this in the TIDA-01102 reference design. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Genius 13200 points

    Hi Beigel-san,

    Thanks for your prompt responses.

    Yes, it seems that they wants to switch the address dynamically. but I push I2C switches so many time but they haven't disclose why they want to do that. 

    Sorry, I have three more questions below. Could you help me to answer to the customer?

    1. SD pin wait time

    Could you tell me recovering time from shutdown mode after Lo to high transition? can they refer tWAKEUP for this?
    Please tell me how long they need to wait changing ADDR logic level after high to low transition as well...

    2. tWAKEUP definition

    According to the datasheet, this period indicates "Wake-up Time from SD high-low transition to I2C readback"
    It means the waiting time from the transition to the throwing of the I2C first command, right?

    3. Driving current change procedure

    When changing the drive current setting in Active mode, is it sufficient to change the Is it enough to change the DRIVE_CURRENTx setting?

    Regards,

    Takashi Onawa

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 18545 points

    Hello Onawa-san, 

    1. We don't have the timing requirement for this documented, but waiting the same amount of time for tWAKEUP (2ms) would be sufficient to ensure there isn't any issue in switching the address. 
    2. Yes, the tWAKEUP time is from when the SD pin transitions to when I2C commands can be processed by the device. 
    3. Yes, you can just change the drive current using the register settings. When the RP_OVERRIDE_EN setting is used, the device will automatically adjust the drive current. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Genius 13200 points

    Hi Beigel-san,

    Thanks for your prompt response on this. Sorry, I got one more questions from them today.

    Regarding No.1 question above, they understood that 2ms wait is enough for SD to SLEEP transition but how much do they need to wait for SLEEP to Active mode transition? 

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 18545 points

    Hello Onawa-san, 

    When going into active mode, the main timing delay at the start of sampling is the sensor activation time. 

    This timing changes based on the sensor design and device configuration. 

    Best Regards, 

    Justin Beigel