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LM73-Q1: Start-Up Related Questions

Kenichiro
Mastermind 9165 points
Part Number: LM73-Q1
Other Parts Discussed in Thread: LM73

[ LM73-Q1 ] Start-Up Related Questions

Hi,

Can you help me to address some start-up questions below?

<Q1>:

Are there any wait time requirements after power-up before starting I2C communication?


<Q2>:

My customer would perform following initialization sequence together with full power down reset.
Do you see any problems?

  1. Power-Up
  2. Write 0xC0 to 0x01(Pointer Address)
  3. Wait 500mS or 1000mS
  4. Write 0x40 to  0x01(Pointer Address) 
  5. Write 0x2A80 (85deg C for upper limit with 11bit)
  6. Write 0x2800 (-80deg C for lower limit with 11bit)
  7. Write 0x48 to 0x01(Pointer Address)

<Q3>:

Any of requirements on maximum duration of hold time of Full Power Down bit 1?
As per datasheet, hold time should be around 14mS.
If customer hold it long as several hundred ms (such as 500mS, 1000mS as above), does this cause any of issues?



Thank you for your support in advance.
Regards,
Ken


<Other Reference Posts, Before Posting>:

LM73 / software reset sequence
e2e.ti.com/.../530548

  • 0
    TI__Mastermind 36930 points
    Hi Ken,

    Question 1: When the device reaches to POR voltage: 1.66V (-40°C), 1.7V (25°C), and 2.1V (150°C) or POR during 2.7V to 3.3V, it is required 1ms and additonal one temperature converstion time depends on the resolution/conversion rate you are setting to.

    Question 2: Everything looks fine except item 6 and 7. For item 6, the device only support down to -40°C, setting to -80°C for Tlow the device will never trip. For item 7, the ALERT pin is an open drain otuput pin where it is being pull-up with a resistor, setting bit D3 will place ALERT pin to low and clear the status.

    Question 3: You are correct ath the underline in red indicated that you must provide at least 14ms in order to complete the POR. I would suggest that taking to 120ms or 500ms should be fine, but 1000ms might be too long.

    Hope this helps.
    Aaron
  • 0 in reply to Aaron Heng
    Mastermind 9165 points
    Thanks, Aaron!