DS1864T+ Maxim Integrated Products, DS1864T+ Datasheet - Page 22

• Manufacturer Part Number: DS1864T+
• Description: IC LASER CTRLR 1CHAN 5.5V 28TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Controller (Fiber Optic)r

Specifications of DS1864T+

• Number Of Channels: 1
• Voltage - Supply: 2.97 V ~ 5.5 V
• Current - Supply: 3mA
• Operating Temperature: -40°C ~ 95°C
• Package / Case: 28-WFQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SFP Laser Controller and
Diagnostic IC
Table 04h (Table 01h in DS1859 configuration) is the
location of the LTXP programmable threshold. Register
DDh of Table 04h (Table 01h in DS1859 configuration)
is the location of the LOS programmable threshold.
There are ten comparators for alarms and ten compara-
tors for warnings for the five analog channels: V
Temperature, MON1, MON2, and MON3. These com-
parators have high and low threshold limits, which are
used to determine when alarm and warning flags are
triggered. A high alarm flag occurs when a comparator
determines if the monitored analog value is above a
programmable threshold. A low alarm flag occurs when
a comparator determines if the monitored analog value
is below a programmable threshold. The same applies
for high and low warning flags, though warning flags
are typically set to trip prior to the alarm flags. The pro-
grammable thresholds have a 2-byte set point in the
same format as the ADC values stored in Lower
Memory bytes 60h through 69h. The programmable
high and low thresholds for both alarms and warnings
are located in Lower Memory bytes 00h through 27h.
The status bits for the alarm flags are located in Lower
Memory bytes 70h and 71h. The status bits for the
warning flags are located in Lower Memory bytes 74h
and 75h. A high alarm or warning flag is set to a 1 when
the corresponding digital value exceeds the user pro-
grammed high threshold. A low alarm or warning flag
is set to a 1 when the corresponding digital value
goes below the user-programmed low threshold.
Comparisons of all measured values with high and low
alarm and warning limits are done automatically.
The MASK bits control which flags can assert the mask-
able interrupt bit, MINT (bit 0, address 71h of the Lower
Memory). The MASK bits are located in Table 01h,
bytes F8h through FBh, or Table 05h, bytes F8h
through FBh, depending on the state of the MASK bit
(Table 04h (Table 01h in DS1859 configuration), byte
DAh, bit 0). If the MASK bit is 0, then the values in
addresses F8h through FBh in Table 05h will determine
which flags will assert MINT. If the MASK bit is 1, then
the values in addresses F8h through FBh in Table 01h
(Table 00h in DS1859 configuration) will determine
which flags will assert MINT.
The TX-F pin is used to indicate a DAC shutdown and/or
laser fault. See the logic diagram in Figure 12. The
TXDC control bit (bit 6, byte 6Eh of the Lower Memory)
is a software-controllable shutdown feature. It not only
triggers TX-F to go active when set to a 1, but will also
disable the DACs, shutting down the laser. The TX-D pin
acts like a hardware version of the TXDC bit, triggering
22
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TX-F, INTX-F, and TX-D
Alarms and Warnings
CC
,
the TX-F pin and disabling the DACs when set high. The
MINT interrupt bit discussed earlier also can trigger the
TX-F pin if configured to enable when one of its alarm or
warning flags goes high. Four fast-trip flags also can
trigger TX-F to go active. The INTX-F pin, used for trig-
gering from an externally generated transmit fault sig-
nal, can also be used to trigger the TX-F pin. The INV bit
(bit 2, byte 89h, Table 04h (Table 01h in DS1859 config-
uration)) is used to invert the polarity of the TX-F pin.
TXF bit (bit 2, byte 6Eh, Lower Memory) is a status bit
that indicates the state of the output pin TX-F. The TX-F
pin is not latched, except in the case of a shutdown
fault. The status of TX-F will reset to inactive upon
removal of the causes of the alarms, or upon resetting of
the shutdown fault. The TX-F pin is open drain.
The RX-LOS pin is used to indicate a loss of received
signal on the MON3 (Received Power) input. RX-LOS
can be triggered by either the external signal, INLOS,
or the internal alarm, LOS flag. INLOS is an input pin
that can be used to indicate a loss of signal generated
from an external source. LOS flag (bit 2, byte 73h of
Lower Memory) can also be used to indicate a loss of
signal. LOS flag is active high when the value of MON3
goes below its threshold, set by programming byte
DDh of Table 04h (Table 01h in DS1859 configuration)
to the desired limit. To configure which signal triggers
RX-LOS, the LOSC bit (bit 6, byte 89h, Table 04h
(Table 01h in DS1859 configuration)) is used. If LOSC
= 1, INLOS is used to trigger the RX-LOS indicator. If
LOSC = 0, then the LOSC flag is used. The final control
bit for this logic is the INVL bit. The INVL bit (bit 0, byte
89h, Table 04h (Table 01h in DS1859 configuration)) is
used to invert the polarity of the RX-LOS pin. The RX-
LOS pin is open drain. See Figure 13 for details.
An auxiliary shutdown signal FETG can be asserted
during a safety fault to disconnect the laser from its
supply as a laser safety disconnect. The polarity of this
signal is determined by the FPOL bit (bit 7, byte DAh in
Table 04h (Table 01h in DS1859 configuration)). If
FPOL is 1, then FETG is high in a shutdown condition. If
FPOL is 0, then FETG is low in a shutdown condition.
A safety fault is a latched event that is generated from
the fast-trip flags (LTXP, HBAL, and HTXP). These flags
can be independently configured to initiate a safety
fault using the enable bits (bits 4, 5, and 6 in byte DAh
of Table 04h (Table 01h in DS1859 configuration)). A 1
for these bits enables that specific flag to generate a
safety fault, while a 0 masks the flag. When a safety
fault is generated, the DACs are disabled (forced to a
high-impedance state), FETG is disabled (driven low),
FETG Laser Safety Features
RX-LOS and INLOS