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Original question:

TLIN1441-Q1: when used in spi mode, i send 0,2,4,6,8,10,12,14,16 to read reg0-reg8, i got the result as follows.

TLIN1441-Q1: Mistakenly entering PIN mode from SPI mode when voltage changes slowly

ying li
Prodigy 70 points
Part Number: TLIN1441-Q1

Dear experts,

As we all kown, LDO outputs voltage not starting from 5V.  And 1441 will check which mode to enter when Vsup >=UVsup, Vcc > UVcc. 

When VCC is increase very slowly at power on or at UVcc event recovery, and our MCU can work normally before VCC < UVcc, there is some chance that 1441 will enter into PIN mode, not SPI mode as expected. Because the nCS pin may be low when the mode check happens. 

How could this problem be solved?

Best, 

Ying

  • TI__Guru 65202 points

    Ying,

    Is PIN mode ever desired in this application? If not, is it possible to place a weak pull-up on pin 9 so that it will have a known state prior to the MCU fully booting up?

    Regards,

    Eric Hackett

  • in reply to Eric Hackett
    Prodigy 70 points

    Hi Eric,

    It's SPI mode. Could you provide the voltage range of PIN9 high and low?

    And if the VCC increase slowly, and the MCU starts communicate with 1441 before UVCC, PIN9 will be low at that time, how so?

    Dose the UVCC monitor can cover this problem?

    Besides, when 1441 jump into sleep mode, the LDO off means no output of VCC or VCC is not 5V, in both PIN mode and SPI mode?

    Best,

    Ying   

  • in reply to ying li
    TI__Guru 65202 points

    Ying,

    I was confused at first, but now I understand, so if your MCU is capable of working prior to the TLIN1441-Q1 fully powering up, couldn't the MCU be used to drive pin 9 high and placing it in SPI mode as VSUP is ramping? Once VSUP crossed the UVVSUP threshold is when the state of pin 9 will be checked.

    Regards,

    Eric Hackett 

  • in reply to Eric Hackett
    Prodigy 70 points

    Hi Eric,

    Sorry for my imprecise expression.

    Our MCU can work normally once VCC is up to 2.7v, and of course PIN9 will be set as high at that time. If MCU need to communicate with 1441, pin9 has to set low. If the mode judgement is finished when the communication starts, SPI mode can enter normally. But if it's not, 1441 may enter in PIN mode, in the case that the judegement happened at pin9 is set low for fullfiling of communication. And if the MCU couldn't konw whether the  mode judegment is finished, when does it start to communicate with 1441? 

    Best,

    Ying

  • in reply to ying li
    TI__Guru 65202 points

    Ying,

    I believe we are addressing this question through email and another thread, so I will be closing this one.

    Regards,

    Eric Hackett