MIC3001 Datasheet, PDF (18/74 Pages) Micrel Semiconductor – SFP Management IC with Internal Calibration

MIC3001
B/ Internal Calibration
If the INTCAL bit in OEMCFG3 is set to 1 (internal calibration
selected), the MIC3001 will process each piece of data
coming out of the A/D converter before storing the result in
memory. Linear slope/offset correction will be applied on a
per-channel basis to the measured values for voltage, bias
current, TX power, and RX power. Only offset correction is
applied to temperature.
The user must store the appropriate slope/offset parameters
in memory at the time of transceiver calibration. In the case
of RX power, a look-up table is provided that implements
eight-segment piecewise-linear correction. This correction
may be performed as temperature compensation or as simple
slope/offset correction. If static slope/offset correction for RX
power is desired, the eight coefficient sets can simply be
made the same. The memory maps for these coefficients are
shown in Table 8 and Table 9.
The slopes allow for the correction of gain errors. Each slope
coefficient is an unsigned, sixteen-bit, fixed-point binary
number in the format:
[mmmmmmmm.llllllll], where m is a data bit (5)
in the most-significant byte and l is a data
bit in the least significant byte
Slopes are always positive. The binary point is in between the
two bytes, i.e., between bits 7 and 8. This provides a numeri-
cal range of 1/256 (0.00391) to 255 in steps of 1/256. The
most significant byte is always stored in memory at the lower
numerical address.
The offsets correct for constant errors in the measured data.
Each offset is a signed, sixteen-bit, fixed-point binary num-
ber. The bit-weights of the offsets are the same as that of the
final results. In the case of temperature, the offset’s least
significant byte (LSB) is always zero since the MIC3001 does
not deal with fractional temperature values. The sixteen bit
offsets provide a numerical range of –32768 to +32767 for
voltage, bias current, transmit power, and receive power. The
numerical range for the temperature offset is –32513 (–128°)
to +32512 (+127°) in increments of 256 (1°). The format for
offsets is:
Micrel
[Smmmmmmmllllllll], where S is the sign bit (6)
(1 = positive, 0 = negative), m is a data bit in
the most-significant byte and l is a data bit in
the least significant byte
The most significant byte is always stored in memory at the
lower numerical address.
Calibration of voltage, bias current, and TX power are per-
formed using the following calculation:
RESULTn = ADC_RESULTn × SLOPEn +
(7)
OFFSETn
Calibration of temperature is performed using the following
calculation:
RESULT = ADC_RESULT + OFFSET
(8)
Calibration of RX power is performed using the following
calculation:
RESULT = ADC_RESULT ×SLOPE(m) +
(9)
OFFSET(m)
where m is the appropriate value from the RX power
calibration look-up table.
The results of these calculations are rounded to sixteen bits
in length. If the seventeenth most significant bit is a one, the
result is rounded up to the next higher value. If the seven-
teenth most significant bit is zero, the upper sixteen bits
remain unchanged. The bit-weights of the offsets are the
same as that of the final results. For SFF-8472 compatible
applications, these bit-weights are given in Table 7.
Parameter
Magnitude of LSB
Temperature
1.0°C⁽¹⁾
Voltage
100µV
Bias Current
2µA
TX Power
0.1µW
RX Power
0.1µW
Table 7. LSB Values of Offset Coefficients
Note:
1. The LSByte of the temperature is always zero.
Address(es)
HEX
DEC
48–49 72–73
4A–4B 74–75
4C–4D
4E–4F
50–51
52–53
54–55
56–57
76–77
78–79
80–81
82–83
84–85
86–87
Field Size
Name
Description
2
RESERVED
Reserved. (There is no slope for temperature.) Do not write; reads unde-
fined.
2
TOFFh:TOFFl
Temperature offset; signed fixed point; LSB is always zero; MSB is at lower
physical address.
2
VSLPh:VSLPl
Voltage slope; unsigned fixed-point; MSB is at lower physical address.
2
VOFFh:VOFFl
Voltage offset; signed fixed point; MSB is at lower physical address.
2
ISLPh:ISLPl
Bias current slope; unsigned fixed-point; MSB is at lower physical address.
2
IOFFh:IOFFl
Bias current offset; signed fixed point; MSB is at lower physical address.
2
TXSLPh: TXSLPl TX power slope; unsigned fixed-point; MSB is at lower physical address.
2
TXOFFh: TXOFFl TX power offset; signed fixed point; MSB is at lower physical address.
Table 8. Internal Calibration Coefficient Memory Map – Part I
M9999-082404
18
August 2004