DS1865T+T&R Maxim Integrated Products, DS1865T+T&R Datasheet - Page 13

• Manufacturer Part Number: DS1865T+T&R
• Description: IC PON CONTROL TRI 28-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of DS1865T+T&R

• Applications: *
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Updates to the TXP-HI, TXP-LO, and BIAS HI quick-trip
alarms do not occur during the burst-enable low time.
Any quick-trip alarm that is detected by default remains
active until a subsequent comparator sample shows the
condition no longer exists.
A second bias-current monitor (BIAS MAX) compares
the DS1865’s BIAS DAC’s code to a digital value stored
in the MAX IBIAS register. This comparison is made
every bias-current update to ensure that a high bias
current is quickly detected.
Monitoring functions on the DS1865 include four quick-
trip comparators and six ADC channels. This monitor-
ing, combined with the interrupt masks, determines
when/if the DS1865 shuts down its outputs and triggers
the TX-F and FETG outputs. All the monitoring levels
and interrupt masks are user programmable.
Four quick-trip monitors are provided to detect potential
laser safety issues. These monitor:
The high and low transmit power quick-trip registers
(HTXP and LTXP) set the thresholds used to compare
against the BMD voltage to determine if the transmit
power is within specification. The HBIAS quick-trip com-
pares the MON1 input (generally from the MAX3643
bias monitor output) against its threshold setting to
determine if the present bias current is above specifica-
tion. The BIAS MAX quick-trip is a digital comparison
that determines if the BIAS DAC indicates that the bias
Figure 3. APC and Quick-Trip Alarm Sample Timing
1) High Bias Current (HBIAS)
2) Low Transmit Power (LTXP)
3) High Transmit Power (HTXP)
4) Max Output Current (MAX IBIAS)
BIAS DAC CODE
SAMPLE TIMES
QUICK-TRIP
Four Quick-Trip Monitors and Alarms
BEN
Monitors and Fault Detection
LAST BURST'S
BIAS SAMPLE
t
FIRST
SAMPLE
BIAS
t
____________________________________________________________________
REP
SAMPLE
BIAS
Monitors
SAMPLE
PON Triplexer Control and
BIAS
SAMPLE
current is above specification. I
exceed the value set in the MAX IBIAS register. When
the DS1865 detects that the bias is at the limit, it sets the
BIAS MAX status bit and holds the bias current at the
MAX IBIAS level. The quick-trips are routed to the TX-F
and FETG outputs through interrupt masks to allow com-
binations of these alarms to be used to trigger these out-
puts. When FETG is triggered, the DS1865 also disables
the MOD and BIAS outputs. See the BIAS and MOD
Output During Power-Up section for details.
The ADC monitors six channels that measure tempera-
ture (internal temp sensor), V
and MON4 using an analog multiplexer to measure
them round-robin with a single ADC. Each channel has
a customer-programmable full-scale range and offset
value that is factory programmed to a default value (see
Table 3). Additionally, MON1–MON4 can right shift
results by up to 7 bits before the results are compared
to alarm thresholds or read over the I
allows customers with specified ADC ranges to cali-
brate the ADC full scale to a factor of 1/2
ified range to measure small signals. The DS1865 can
then right shift the results by n bits to maintain the bit
weight of their specification.
Table 3. ADC Default Monitor Full-Scale
Ranges
BIAS
Temperature (
V
MON1–MON4 (V)
SIGNAL (UNITS)
CC
(V)
SAMPLE
BIAS
Monitoring Circuit
o
C)
SIGNAL
127.996
6.5528
2.4997
+FS
HTXP/LTXP
SAMPLE
SAMPLE
BIAS
Six ADC Monitors And Alarms
CC
7FFF
FFF8
FFF8
HEX
+FS
SAMPLE
HBIAS
, MON1, MON2, MON3,
BIAS
SIGNAL
SAMPLE
is not allowed to
BIAS
-128
-FS
0V
0V
n
2
of their spec-
C bus. This
-FS HEX
8000
0000
0000
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