MIC3000 Datasheet, PDF (24/68 Pages) Micrel Semiconductor – SFP Management IC

MIC3000
The LUTOFF register determines the range of measured
temperatures that are actually spanned by the tables. The
temperature span of the tables versus the value of LUTOFF
is given in Table 16.
LUTOFF
00h
Temperature Span
t_COMP(min) – t_COMP(max)
0°C to +127°C
01h
–2°C to +125°C
02h
–4°C to +123°C
·
·
·
·
·
·
0Fh
–30°C to +97°C
Table 16. Range of Temperature Compensation
Tables vs. LUTOFF
The internal state machine calculates a new table index each
time a new average temperature value becomes available.
This table index is derived from the average temperature
value and LUTOFF. The table index is then converted into a
table address for each of the four look-up tables. These
operations can be expressed as:
Micrel
INDEX = ^TAVG(n) + LUTOFF
2
(7)
where TAVG(n) is the current average temperature; and
TABLE _ ADDRESS = INDEX + BASE _ ADDRESS
where BASE_ADDRESS is the physical base address of
each table, i.e., 00_h, 40_h, 80_h, or C0_h (all tables reside in the
I2CADR+4 page of memory).
At any given time, the current table index can be read in the
LUTINDX register.
Figures 11 and 12 illustrate the operation of the temperature
compensation tables.
Figure 11 is a graphical illustration of the use of the LUTOFF
register to control the temperature range spanned by the
temperature compensation tables. Note that, if the LUTINDX
becomes greater than 63 or less than zero, the maximum or
minimum table value is used, respectively. The tables do not
“roll over.”
LUT(LUTINDX)
+127
(a)
0
63
LUT(t), LUTOFF=0
+127
–128
LUT(t), LUTOFF=07_h
+127
LUT(t), LUTOFF=0F_h
+127
(b) ^{–30°C 0}
–128
+127°C
(c) ^{–30°C 0}
–128
+127°C
+113°C
(d) ^{–30°C 0}
–128
Figure 11. Examples of LUTOFF Operation
+127°C
+98°C
M9999-101204
24
October 2004