MAX3996 Ver la hoja de datos (PDF) - Maxim Integrated
Número de pieza
componentes Descripción
Fabricante
MAX3996 Datasheet PDF : 16 Pages
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3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
Table 2. RTC and RMOD Selection Table
TEMPCO
(ppm/°C)
3500
3000
2500
2000
1500
1000
500
iMOD = 30mA
RMOD (kΩ)
RTC (kΩ)
17.1
1.85
8.04
2.19
5.20
2.68
3.81
3.42
2.98
4.64
2.44
7.08
2.05
14.4
iMOD = 15mA
RMOD (kΩ)
RTC (kΩ)
34.4
3.94
16.3
4.64
10.6
5.62
7.86
7.08
6.21
9.53
5.12
14.4
4.34
29.1
iMOD = 5mA
RMOD (kΩ)
RTC (kΩ)
104
12.3
49.5
14.4
32.4
17.4
24.1
21.8
19.1
29.1
15.9
43.8
13.5
87.8
Table 3. Circuit Responses to Various Single-Point Faults
PIN NAME
CIRCUIT RESPONSE TO OVERVOLTAGE OR
SHORT TO VCC
CIRCUIT RESPONSE TO UNDERVOLTAGE OR
SHORT TO GROUND
TC
Does not affect laser power.
Fault state* occurs.
FAULT
Does not affect laser power.
Does not affect laser power.
TX_DISABLE Modulation and bias current are disabled.
Normal condition for circuit operation.
PORDLY
Does not affect laser power.
Modulation and bias current are disabled.
IN+, IN-
Does not affect laser power.
Does not affect laser power.
MON1
Fault state* occurs.
Does not affect laser power.
MON2
Fault state* occurs.
Does not affect laser power.
COMP
A fault is detected at either the collector or the emitter
of the internal bias transistor, and a fault state* occurs.
If the shutdown circuitry is used, bias current is shut off.
Disables bias current.
MD
SHDNDRV
BIAS
OUT+, OUT-
Disables bias current.
Does not affect laser power. If the shutdown circuitry is
used, bias current is shut off.
In this condition, laser forward voltage is 0V and no
light is emitted.
Does not affect laser power.
The APC circuit responds by increasing bias current
until a fault is detected at the emitter or collector of the
bias transistor, and then a fault* state occurs.
Does not affect laser power.
Fault state* occurs. If the shutdown circuitry is used,
bias current is shut off.
Does not affect laser power.
MODSET Does not affect laser power. Fault* state may occur.
Fault state* occurs.
*A fault state asserts the FAULT pin, disables the modulator outputs, disables the bias output, and asserts the SHDNDRV pin.
IC pins. See Table 3 to view the circuit response to vari-
ous single-point failures. The shutdown condition is
latched until reset by a toggle of TX_DISABLE or VCC.
Fault Detection
All critical nodes are monitored for safety faults, and
any node voltage that differs significantly from its
expected value results in a fault (Table 1). When a fault
condition is detected, the laser is shut down. See the
Applications Information for more information on laser
safety.
Shutdown
The laser driver offers redundant bias shutdown. The
SHDNDRV output drives an optional external transistor.
The bias and modulation drivers have separate internal
disable signals.
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