ADN2871ACPZ-RL7 Analog Devices Inc, ADN2871ACPZ-RL7 Datasheet - Page 18

• Manufacturer Part Number: ADN2871ACPZ-RL7
• Description: IC,Laser Diode/LED Driver,LLCC,24PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of ADN2871ACPZ-RL7

• Data Rate: 4.25Gbps
• Number Of Channels: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 32mA
• Current - Modulation: 90mA
• Current - Bias: 100mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-VFQFN, CSP Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADN2871
ALARMS
The ADN2871 has a latched, active high monitoring alarm
(FAIL). The FAIL alarm output is an open drain in conformance
to SFP MSA specification requirements.
The ADN2871 has a three-fold alarm system that covers
•
•
•
The bias current alarm trip point is set by selecting the value
of resistor on the IBMON pin to GND. The alarm is triggered
when the voltage on the IBMON pin goes above 1.2 V. FAIL is
activated when the single-point faults in Table 5 occur. The
Table 5. ADN2871 Single-Point Alarms
Alarm Type
Bias Current
MPD Current
Crucial Nodes
Table 6. ADN2871 Response to Various Single-Point Faults in AC-Coupled Configuration (as shown in Figure 35)
Pin
CCBIAS
PAVSET
PAVREF
RPAV
PAVCAP
DATAP
DATAN
ALS
ERSET
IMMON
ERREF
IBMON
FAIL
IMODP
IMODN
IBIAS
Use of a bias current higher than expected, probably as a
result of laser aging.
Out-of-bounds average voltage at the monitor photodiode
(MPD) input, indicating an excessive amount of laser
power or a broken loop.
Undervoltage in the IBIAS node (laser diode cathode) that
would increase the laser power.
Fault state occurs
Does not increase laser average power
Voltage mode: Fault state occurs
Does not increase laser average power
Short to V
Fault state occurs
Fault state occurs
Voltage mode: Fault state occurs
Resistor mode: Tied to V
Voltage mode: Fault state occurs
Resistor mode: Tied to V
Does not increase laser average power
Does not increase laser average power
Output currents shut off
Does not affect laser power
Resistor mode: Tied to V
Fault state occurs
Fault state occurs
Does not increase laser average power
Fault state occurs
Mnemonic
IBMON
PAVSET
ERREF (the ERRREF
designed tied to
V
setting mode)
IBIAS
CC
in resistor
CC
CC
CC
CC
Overvoltage or Short to V
Alarm if > 1.2 V typical (±10% tolerance)
Alarm if > threshold (typical threshold: 1.5 V to 2.1 V)
Alarm if shorted to V
voltage setting mode only)
Ignore
CC
Short to GND
Fault state occurs
Fault state occurs
Fault state occurs
Fault state occurs
Fault state occurs
Does not increase laser average power
Does not increase laser average power
Normal currents
Does not increase laser average power
Does not increase laser average power
Voltage mode: Does not increase
average power
Resistor mode: Fault state occurs
Does not increase laser average power
Does not increase laser average power
Does not increase laser average power
Does not increase laser average power
Fault state occurs
(the alarm is valid for
Rev. A | Page 18 of 20
CC
Condition
circuit in Figure 37 can be used to indicate that FAIL has been
activated while allowing the bias and modulation currents to
remain on. The transistor’s V
1.3 V disabling the automatic shutdown of bias and modulation
currents. If an alarm has triggered and FAIL is activated, ALS
can be brought high and then low to clear the alarm.
Undervoltage or Short to GND Condition
Ignore
Alarm if < threshold (typical threshold: 0.6 V to 1.1 V)
Ignore
Alarm if shorted to GND
ADN2871
Figure 37. FAIL Indication Circuit
FAIL
Open
Does not increase laser average power
Fault state occurs
Fault state occurs
Circuit designed to tie to V
setting mode, so no open case
Voltage mode: Fault state occurs
Resistor mode: Does not increase
average power
Fault state occurs
Does not increase laser average power
Does not increase laser average power
Output currents shut off
Does not increase laser average power
Does not increase laser average power
Does not increase laser average power
Does not increase laser average power
Does not increase laser average power
Does not increase laser average power
Does not increase laser power
Fault state occurs
BE
clamps the FAIL voltage to below
10kΩ
R1
V
CC
Q1
NPN
R2
330Ω
LED
D1
CC
in resistor