DS1878T+T&R Maxim Integrated Products, DS1878T+T&R Datasheet - Page 16

• Manufacturer Part Number: DS1878T+T&R
• Description: IC CTLR SFP W/DGTL LDD RX 28TQFN
• Manufacturer: Maxim Integrated Products
• Type: SFP+ Controllerr

Specifications of DS1878T+T&R

• Input Type: *
• Output Type: *
• Interface: *
• Current - Supply: *
• Mounting Type: Surface Mount
• Package / Case: 28-WFQFN exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SFP+ Controller with Digital LDD Interface
An APC sample that requires an update of the BIAS
register causes subsequent APC samples to be
ignored until the end of the 3-wire communication that
updates the laser driver’s BIAS DAC, plus an additional
16 sample periods (t
Monitoring functions on the device include five quick-trip
comparators and six ADC channels. This monitoring
combined with the alarm enables (Table 01h/05h) deter-
mines when/if the device turns off the Maxim laser dri-
ver’s DACs and triggers the TXFOUT and TXDOUT
outputs. All the monitoring levels and interrupt masks are
user programmable.
Five quick trip monitors are provided to detect potential
laser safety issues and LOS status. These monitor the
following:
1) High Bias Current (HBATH), causing QT BIAS HI
2) Low Transmit Power (LTXP), causing QT TXP LO
3) High Transmit Power (HTXP), causing QT TXP HI
4) Max Output Current (IBIASMAX), causing QT BIAS
5) Loss of Signal (LLOS), causing QT LOS LO
The high and low transmit power quick-trip registers
(HTXP and LTXP) set the thresholds used to compare
against the MON2 voltage to determine if the transmit
power is within specification. The HBATH quick trip
compares the MON1 input (generally from a Maxim
laser driver bias monitor output) against its threshold
setting to determine if the present bias current is above
specification. The user can program up to eight differ-
ent temperature-indexed threshold levels for HBATH
(Table 02h, Registers D0h–D7h).
The BIAS MAX quick trip compares the BIAS register
with the MON2 voltage and determines if the BIAS reg-
ister is above specification. The BIAS register is not
allowed to exceed the value set in the IBIASMAX regis-
ter. When the device detects the bias is at the limit, it
sets the BIAS MAX status bit and holds the BIAS regis-
ter setting at the IBIASMAX level.
Table 3. ADC Default Monitor Full-Scale Ranges
16
Temperature (°C)
V
MON1–MON4 (V)
CC
MAX
(V)
______________________________________________________________________________________
SIGNAL (UNITS)
Five Quick-Trip Monitors and Alarms
Monitors and Fault Detection
REP
).
+FS SIGNAL
Monitors
127.996
6.5528
2.4997
The LOS LO quick trip compares the MON3 input
against its threshold setting (LLOS) to determine if the
present received power is below the specification. The
LOS RANGING register allows the LOS threshold value
to scale. The LOS LO quick trip can be used to set the
LOSOUT pin. LOS HI does not set LOSOUT. See the
description of the LOS LO and LOS HI bits (Table 01h,
Register FBh) for further details of operation.
The quick trips are routed to create TXFOUT through
interrupt masks to allow combinations of these alarms
to be used to trigger the outputs.
The ADC monitors six channels that measure tempera-
ture (internal temp sensor), V
using an analog multiplexer to measure them round
robin with a single ADC (see the ADC Timing section).
The five voltage channels have a customer-programma-
ble full-scale range and all channels have a customer-
programmable offset value that is factory programmed to
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
bus. This allows customers with specified ADC ranges to
calibrate the ADC full scale to a factor of 1/2
specified range to measure small signals. The device
can then right-shift the results by n bits to maintain the bit
weight of their specification (see the Right-Shifting ADC
Result and Enhanced RSSI Monitoring (Dual-Range
Functionality) sections).
The ADC results (after right-shifting, if used) are com-
pared to the alarm and warning thresholds after each
conversion, and the corresponding alarms are set,
which can be used to trigger the TXFOUT output.
These ADC thresholds are user programmable, as are
the masking registers that can be used to prevent the
alarms from triggering the TXFOUT output.
There are six analog channels that are digitized in a
round-robin fashion in the order shown in Figure 5. The
total time required to convert all six channels is t
the Analog Voltage Monitoring Characteristics for
details).
+FS HEX
7FFF
FFF8
FFF8
-FS SIGNAL
Six ADC Monitors and Alarms
-128
0
0
CC
, and MON1–MON4
-FS HEX
ADC Timing
8000
0000
0000
n
RR
of their
(see
2
C