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Original question:

INA236: VIL threshold confirmation

TCA9511A: I2C level converter IC selection for INA236

Masami Akazawa
Intellectual 535 points
Part Number: TCA9511A
Other Parts Discussed in Thread: INA236, , TCA9803, ISO1643

Hi team!

1.Could you please tell me whether the TCA95711 really recognizes low level at 0.3*Vcc?

2. I would like to use the INA236 to communicate with an isolator whose VOL is 0.6 to 0.8V.
Will this be possible if I use the TCA9511A? 

In other words:
Isolator <-> TCA9511A <-> INA236 (Vcc and VS are 5V)

isolator:VIL=0.5V, VOL=0.6 to 0.8V

TCA9511A:VIL=0.3*Vcc(1.5V), VOL=0.4V

INA236: VIL=0.4V, VOL=0.3V

Best regards 

  • +1
    TI__Guru 54798 points

    Hi Masami,

    Masami Akazawa said:
    1.Could you please tell me whether the TCA95711 really recognizes low level at 0.3*Vcc?

    The internal rise-time accelerators trigger when VIL = 0.6V. The VIL of the TCA9511A is ~ 0.6V - VOS to 0V. 

    For example, if your VOL = 100mV on SDAIN/SCLIN, then SDAOUT/SCLOUT = VOL + VOS = 100mV + 60 mV = 160 mV. 

    The acceptable VIL range is therefore the RTA threshold voltage - offset voltage (max). 0.6V - 100mV = 0.5V. 

    0V < VIL < 0.5V is the VIL range for this buffer. 

    Masami Akazawa said:

    2. I would like to use the INA236 to communicate with an isolator whose VOL is 0.6 to 0.8V.
    Will this be possible if I use the TCA9511A? 

    In other words:
    Isolator <-> TCA9511A <-> INA236 (Vcc and VS are 5V)

    isolator:VIL=0.5V, VOL=0.6 to 0.8V

    TCA9511A:VIL=0.3*Vcc(1.5V), VOL=0.4V

    INA236: VIL=0.4V, VOL=0.3V

    In this case, the isolator's output voltage is too large to work with TCA9511A. 

    Have you considered using TCA9803 with A-side facing the isolator and B-side facing the INA236 device? 

    The TCA9803 B-side requires no external PU resistors exist on B-side as it uses an internal current source for the PU current. It's VOLB is very low and within the spec of the INA device. One downside is that this device is only rate for 3.6V. VILA = 0.3 x VCCA. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Intellectual 535 points

    Hi Tyler,

    Thank you.

    Your post made me understand that there is a problem with the TCA9511.

    I am planning to change the isolator and make Side2 of the ISO1643 the INA side. Is this okay? :

    [Vcc is 5V] Host<-->(SIDE1)ISO1643(SIDE2)<-->INA236 [Vcc and VS are 5V]

    Host: VIL=0.3*Vcc(1.5V),VOL(actual value)=0.1V

    ISO1643 (SIDE1): VIL=0.48V, VOL=0.4V

    ISO1643 (SIDE2): VIL=0.3*Vcc(1.5V), VOL=0.4V

    INA236: VIL=0.4V, VOL=0.3V

    I will also consider the TCA9803.

    Best regards,

    Masami

  • 0 in reply to Masami Akazawa
    TI__Guru 54798 points

    Hi Masami,

    This implementation looks better. 

    As long as the VOL's of the ISO164x device are compatible to the logic levels of the INA236 and Host controller, we are good. 

    Masami Akazawa said:

    [Vcc is 5V] Host<-->(SIDE1)ISO1643(SIDE2)<-->INA236 [Vcc and VS are 5V]

    Host: VIL=0.3*Vcc(1.5V),VOL(actual value)=0.1V

    ISO1643 (SIDE1): VIL=0.48V, VOL=0.4V

    ISO1643 (SIDE2): VIL=0.3*Vcc(1.5V), VOL=0.4V

    INA236: VIL=0.4V, VOL=0.3V

     I don't support the isolated buffers, but based off the EC table of the datasheet, it looks good. 

    Regards,

    Tyler