MIC3001 Datasheet, PDF (24/74 Pages) Micrel Semiconductor – SFP Management IC with Internal Calibration

MIC3001
V_DDA
Saturation Detector
95% V_DDA
5% V_DDA
SATURATION_FAULT
V_COMP
t_FLTTMR
COUNTER
FLTTMR
Figure 10. Saturation Detector
CNTRL
LOS
VRX
LOSFLT
LOSFLTn
D1
2:1
MUX
D0
FLTDAC
OEMCFG3
LOS
DIS
V_DDA
RXLOS
Figure 11. RXLOS Comparator Logic
Micrel
Temperature Measurement
The temperature-to-digital converter for both internal and
external temperature data is built around a switched current
source and an eight-bit analog-to-digital converter. The tem-
perature is calculated by measuring the forward voltage of a
diode junction at two different bias current levels. An internal
multiplexer directs the current source’s output to either an
internal or external diode junction. The value of the ZONE bit
in OEMCFG1 determines whether readings are taken from
the on-chip sensor or from the XPN input. The external PN
junction may be embedded in an integrated circuit, or it may
be a diode-connected discrete transistor. This data is also
used as the input to the temperature compensation look-up
tables. Each time temperature is sampled and an updated
value acquired, new corrective values for I_MOD and the APC
setpoint are read from the corresponding tables, added to the
set values, and transferred to DACs.
Diode Faults
The MIC3001 is designed to respond in a failsafe manner to
hardware faults in the temperature sensing circuitry. If the
connection to the sensing diode is lost or the sense line is
shorted to V_DD or ground, the temperature data reported by
the A/D converter will be forced to its full-scale value (+127°C).
The diode fault flag, DFLT, will be set in OEMCFG1, TXFAULT
will be asserted, and the high temperature alarm and warning
flags will be set. The reported temperature will remain +127°C
until the fault condition is cleared. Diode faults may be reset
by toggling TXDISABLE, as with any other fault. Diode faults
will not be detected at power up until the first A/D conversion
cycle is completed. Diode faults are not reported while
TXDISABLE is asserted.
M9999-082404
24
August 2004