LM75B / about I2C digital switching characteristics

Toshiyuki

Other Parts Discussed in Thread: LM75B, TMP75B

Hi,

Customer is considering LM75B. Then, the device is assured t1,SCL Period (MIN)=2.5us. It is 400kHz(MAX) in other words.

If SCL clock has 50% duty, the low of t1≒1.25us for 400kHz. However, tlow is defined as 1.3us(min) as follows. I believe that the setting seems to violate I2C specification.

http://www.nxp.com/documents/user_manual/UM10204.pdf

Could the LM75B be used with SCL=400kHz(Duty=50%)?

Best Regards,

Kato

over 7 years ago

0 Ren Schackmann over 7 years ago

TI__Mastermind 35895 points

Yes, The LM75B can be used with SCL=400kHz 50% duty cycle.

Ren

0 Toshiyuki over 7 years ago in reply to Ren Schackmann

Mastermind 7075 points

Hi Ren - san,

Thank you for the reply. Would you provide us information of the following I2C spec ?

・LOW period of the SCL clock of Fast mode = 1.2us(Min)

Since customer is considering that they must ensure the I2C spec, they doubt that LM75B is used with SCL=400kHz 50% duty cycle.

Best Regards,

Kato

0 Ren Schackmann over 7 years ago in reply to Toshiyuki

TI__Mastermind 35895 points

Our spec would be tLOW = 1.25uS at 400kHz.

If this explanation is not satisfactory for your customer, could you please suggest TMP75B instead? It is drop-in replacement for LM75B with a more robust serial interface. It can achieve 3MHz communication and has lower current consumption.

Ren

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LM75B / about I2C digital switching characteristics