For telemetry and configuration parameters, the TPS1689 supports DIRECT format. Digital codes for telemetry or configuration parameters can be converted to their equivalent real world units using Equation 11 and Equation 12.

• Interpreting received values:

  The host system uses Equation 11 to convert the value received from the PMBus® device into a reading of V, A, °C, or W:

  Equation 11. $X=\frac{1}{m}\left(Y\times {10}^{-R}-b\right)$

  Where:

  • X, is the calculated, “real world” value in the appropriate units (V, A, °C, or W);

  • m, the slope coefficient, is a two byte, two’s complement integer;

  • Y, is a two byte two’s complement integer received from the PMBus® device;

  • b, the offset, is a two byte, two’s complement integer; and

  • R, the exponent, is a one byte, two’s complement integer.

• Sending a value:

  To send a value, the host must use Equation 12 to find the value of Y:

  Equation 12. $Y=\left(mX+b\right)\times {10}^R$

  Where:

  • Y is the two byte two’s complement integer to be sent to the unit;

  • m, the slope coefficient, is the two byte, two’s complement integer;

  • X, a “real world” value, in units such as V, A, °C, or W, to be converted for transmission;

  • b, the offset, is the two byte, two’s complement integer; and

  • R, the exponent, is the decimal value equivalent to the one byte, two’s complement integer.