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BQ34Z100-G1: Protection Diode for SDA and SCL

Charles-Elie Demarty
Intellectual 725 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100

Hi, 

My question is about protection diode for communication pin. The document mentions a max voltage of 5.5V max.

However, Your schematic of demo board integrates diodes zener 5.6V (AZ23C5V6-7). It's normal ?? (we could think of putting diodes of smaller voltage)

Moreover, you mention a min voltage of "Vcc-0.5V". And Vcc = -0.3V to 2.75V. But there is not Vcc pin on BQ34z100-G1.

Can you explain to me Vcc please ?

  • 0
    TI__Mastermind 25955 points
    Hi Charles-Elie,

    The supply voltage (V REGIN) of the device must be between 2.45 and 4.5 V for the device to operate. Keep the voltage between 2.7 and 4.5 V for flash writes and 2.45 to 2.7 V with no flash writes.

    Please size the diodes to your application. The clamp circuit may be replaced by your own power rail.

    In this case Vcc may refer to REG25.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Intellectual 725 points

    Hello Bryan, 

    VREGIN is always between 2.45 and 4.5V (we use TPS7A1633DRBT).

    But for your information, pull-up resistors are not integrated in our circuit. Here the schematic :

    "Please size the diodes to your application." => Our goal is to protect the communication pins of the BQ34z100 for a maximum of cases. Applications can be diverse and varied, 

    If I understand correctly: do not have a zener diode under 4.5V and above 5.5V . That's why I was surprised to see 5.6V diode, and I wondered if there was any reason.

    Best regards.

  • 0 in reply to Charles-Elie Demarty
    Intellectual 725 points
    Hi,

    In the datasheet, in part "Absolute Maximum Ratings" - Viod (Open-drain I/O pins (SDA, SCL, HDQ, VEN)) : max voltage = 5.5V.
    And, in part 'Recommended Operating Conditions' - VIH(OD) (Input voltage, high (SDA, SCL,HDQ)) : max voltage = 6V.

    It is amazing to see an operating condition higher than the max conditions.
    It's a mistake ? What is the actual max voltage not to be exceeded? (for SDA, SCL,HDQ)

    Best regards.
  • 0 in reply to Charles-Elie Demarty
    TI__Mastermind 25955 points
    Hi Charles-Elie,

    Thank you for the feedback. The systems team has been notified. Please stick to the Absolute Maximum Ratings Value of 5.5 V.

    Sincerely,
    Bryan Kahler