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SLDM-06D1Ax

tech.support@psbel.com

belpowersolutions.com

51. MEASURING OUTPUT CURRENT USING THE PMBUS

The module measures current by using the inductor winding resistance as a current sense element. The inductor winding resistance is then the

current gain factor used to scale the measured voltage into a current reading. This gain factor is the argument of the IOUT_CAL_GAIN

command, and consists of two bytes in the linear data format. The exponent uses the upper five bits [7:3] of the high data byte in two-s

complement format and is fixed at –15 (decimal). The remaining 11 bits in two’s complement binary format represent the mantissa.

The current measurement accuracy is also improved by each module being calibrated during manufacture with the offset in the current reading.

The IOUT_CAL_OFFSET command is used to store and read the current offset. The argument for this command consists of two bytes composed

of a 5-bit exponent (fixed at -4d) and a 11-bit mantissa. This command has a resolution of 62.5mA and a range of -4000mA to +3937.5mA.

During manufacture, each module is calibrated by measuring and storing the current gain factor and offset into non-volatile storage.

The READ_IOUT command provides module average output current information. This command only supports positive or current sourced from

the module. If the converter is sinking current a reading of 0 is provided. The READ_IOUT command returns two bytes of data in the linear data

format. The exponent uses the upper five bits [7:3] of the high data byte in two-s complement format and is fixed at –4 (decimal). The remaining

11 bits in two’s complement binary format represent the mantissa with the 11th bit fixed at 0 since only positive numbers are considered valid.

Note that the current reading provided by the module is not corrected for temperature. The temperature corrected current reading for module

temperature TModule can be estimated using the following equation

where IOUT_CORR is the temperature corrected value of the current measurement, IREAD_OUT is the module current measurement value,

TIND is the temperature of the inductor winding on the module. Since it may be difficult to measure TIND, it may be approximated by an estimate

of the module temperature.

52. Measuring Output Voltage Using the PMBus

The SLDM-06D1Ax module can provide output voltage information using the READ_VOUT command. The command returns two bytes of data

all representing the mantissa while the exponent is fixed at -10 (decimal).

During manufacture of the module, offset and gain correction values are written into the non-volatile memory of the module. The command

VOUT_CAL_OFFSET can be used to read and/or write the offset (two bytes consisting of a 16-bit mantissa in two’s complement format) while

the exponent is always fixed at -10 (decimal). The allowed range for this offset correction is -125 to 124mV. The command VOUT_CAL_GAIN

can be used to read and/or write the gain correction - two bytes consisting of a five-bit exponent (fixed at -8) and a 11-bit mantissa. The range of

this correction factor is -0.125V to +0.121V, with a resolution of 0.004V. The corrected output voltage reading is then given by:

53. MEASURING INPPUT VOLTAGE USING THE PMBUS

The SLDM-06D1Ax module can provide output voltage information using the READ_VIN command. The command returns two bytes of data in

the linear format. The upper five bits [7:3] of the high data form the two’s complement representation of the mantissa which is fixed at –5

(decimal). The remaining 11 bits are used for two’s complement representation of the mantissa, with the 11th bit fixed at zero since only positive

numbers are valid.

During module manufacture, offset and gain correction values are written into the non-volatile memory of the module. The command

VIN_CAL_OFFSET can be used to read and/or write the offset - two bytes consisting of a five-bit exponent (fixed at -5) and a11-bit mantissa in

two’s complement format. The allowed range for this offset correction is -2 to 1.968V, and the resolution is 32mV. The command VIN_CAL_GAIN

can be used to read and/or write the gain correction - two bytes consisting of a five-bit exponent (fixed at -8) and a 11-bit mantissa. The range of

this correction factor is -0.125V to +0.121V with a resolution of 0.004V. The corrected output voltage reading is then given by:

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