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Delivering Next Generation Technology Series
FGSD12SR6003*A
3-14.4Vdc Input, 3A, 0.45-5.5Vdc Output
Http://www.fdk.com Ver 2.3 Oct. 26, 2016
Data Sheet
Measurement of Output Current, Output
Voltage and Input Voltage
The module is capable of measuring key module
parameters such as output current and voltage and
input voltage and providing this information through the
PMBus interface. Roughly every 200us, the module
makes 16 measurements each of output current,
voltage and input voltage. Average values of of these
16 measurements are then calculated and placed in
the appropriate registers. The values in the registers
can then be read using the PMBus interface.
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.
Measuring Output Voltage Using the PMBus
The 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:
Measuring Input Voltage Using the PMBus
The 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 a
11-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
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