LTC2927 Powersequencing

Question

In electrical characteristics section of the datasheet of the LTC2947, it is mensioned that the OVDD should be applied earlier or at the same time as AVCC/DVCC. In our application however the OVDD is generated from the Input supply we want to monitor. This input supply is also connected to AVCC/DVCC like the example in "Typical Application" of the datasheet. 
 Furthermore in the "Digital Interface" section following is mentioned: 
 Selecting SPI or I2C Serial Interface The serial interface of the LTC2947 can operate in either SPI or I2C mode. To select SPI mode, tie AD0 to OVDD. To select I2C mode, connect AD0 according to Table 3. The LTC2947 selects SPI or I2C mode by reading pin AD0 when DVCC is powered up. To ensure proper mode detection, OVDD should be powered up before DVCC. 
 In our case we would like to use I2C mode and will connect AD0 to GND. Does the LTC2927 work properly in I2C mode if we apply OVDD after AVCC/DVCC 
 Regards, 
 Marcel

blovell · Accepted Answer

Greetings Marcel, 
 It should be fine for you to bring up OVDD after AVCC/DVCC in this specific case, where you are using I2C and have AD0 tied to GND. This would not work in SPI mode however. In your case, the I2C communication will not come up instantaneously, as the part needs to come out of UVLO before it can begin checking what it's address is. After that, the part should operate normally. Let me know if you have any further questions! 
 Thank you and best regards, 
 Brad)

blovell · Answer

Hi Brian, 
 It should. Just as above though, it will not come up instantaneously. 
 Thank you and best regards, 
 Brad

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LTC2927 Powersequencing