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參數(shù)資料
| 型號： | MAX3667 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Single LVDS Transmitter 5-SOT-23 -40 to 85 |
| 中文描述： | +3.3V、622Mbps、 SDH/SONET激光驅(qū)動器，帶有自動功率控制 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 138K |
| 代理商： | MAX3667 |
Since the PDJ will change with changes in loop gain, it
is important to choose capacitor values that are as
large as is physically possible. Since each capacitor
represents a different pole, for stability reasons, C
APC
should be kept substantially smaller than C
COMP
. It is
recommended that the value of C
APC
be set 1000 times
smaller than C
COMP
.
The time constant associated with the DC blocking
capacitor on IMOD can also have an effect on PDJ . It is
important that this time constant produce minimum
droop for long consecutive bit streams.
Referring to Figure 3, the droop resulting from long time
periods without transitions can be represented by the
following equation:
APC operation assures that the discharge level for
τ
is
P
AVG
. An overall droop of 6% relative to P
p-p
equates
to a 12% droop relative to P
AVG
. To ensure a droop of
less than 12% (6% relative to P
p-p
), this equation can
be solved for
τ
as follows:
If t
1
equals 100 consecutive unit intervals without a
transition, then the time constant associated with the
DC blocking capacitor needs to be longer than:
τ
AC
≥
R
AC
C
AC
= 7.8 (100 bits) (1.6ns/bit) = 1.25μs
The estimated value of R
AC
is:
R
AC
= 31
R
FILT
(R
DAMP
+ r
LASER
)
Assuming R
FILT
= 22
, R
DAMP
= 4.7
, and r
LASER
= 4
:
R
AC
= 5.2
with C
AC
= 1μF,
τ
AC
= 5.2μs.
Operation without APC (open loop)
When operating without APC, be sure to configure the
MAX3667 as follows:
1) Disconnect APC from BIASSET.
2) Force a voltage of 1V to 2V at APC to prevent the
OTA from saturating.
3) Disconnect the monitor diode.
4) Pull up the MD pin to V
CC
through a 5k
resistor.
5) Pull down the COMP pin to ground through a 30k
resistor.
Remember that the bias-current output is programmed
by adjusting the BIASSET resistor when the APC loop is
disconnected.
Output Current Limits
The MAX3667 is equipped with output current limiting
and short-circuit protection. In +3.3V operation, I
BIAS
is
limited to approximately 170mA open loop, and I
QMOD
is limited to approximately 140mA (see Typical
Operating Characteristics). In +5.0V operation, I
BIAS
is
limited to approximately 300mA, and I
QMOD
is limited
to approximately 140mA.
If BIASSET is shorted to ground, I
BIAS
becomes current
limited. If either APCSET or MODSET is shorted to
ground, the MAX3667 output is turned off. Note that in
5V operation, the I
BIAS
current limit is approximately
300mA. Care should be taken if the MAX3667 is being
used with a laser diode that is sensitive to this current
level.
Interfac e S uggestions
and Laser Compensation
Adding damping resistance in series with the laser
diode (typically 3
to 5
) raises the load resistance,
reduces the load frequency dependence and improves
output aberrations. A series damping resistor of 4.7
is
suggested for the MAX3667.
Series inductance at the cathode of the laser results in
high-frequency loading (V
L
= Ldi/dt) and increased out-
put aberrations. Because of reduced headroom, the
output performance of the transmitted eye diagram can
be significantly impacted during 3.3V operation.
Assuming that laser package series inductance can not
be completely eliminated, a compensation network is
required. With a laser diode load of approximately 4
and 4nH, a series damping resistor of 4.7
, and a cou-
pling capacitor of 0.1μF, a shunt R-C compensation
network of 22
and 0.01μF is recommended (see
Typical Operating Circuit. These values may need to
be adjusted depending on the style of laser used. Note
that it is important to place the compensation network
as close to the load as possible.
[1 - 0.12]
ln
-t
τ
=
= 7.8t
[100% - DROOP] = e
-t
τ
M
+3.3V, 622Mbps S DH/S ONET Laser Driver
with Automatic Power Control
_______________________________________________________________________________________
9
DROOP
t
P
AVG
P
p-p
τ = ∞
τ << τ
AC
τ
AC
t
1
Figure 3. Droop
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX3668 | Single LVDS Transmitter 8-SOIC -40 to 85 |
| MAX3668EHJ | +3.3V, 622Mbps SDH/SONET Laser Driver with Automatic Power Control |
| MAX3669 | Single LVDS Transmitter 8-SOIC -40 to 85 |
| MAX3669EHJ | +3.3V, 622Mbps SDH/SONET Laser Driver with Current Monitors and APC |
| MAX3672 | Low-Jitter 155MHz/622MHz Clock Generator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX3667E/D | 功能描述:激光驅(qū)動器 RoHS:否 制造商:Micrel 數(shù)據(jù)速率:4.25 Gbps 工作電源電壓:3 V to 3.6 V 電源電流:80 mA 最大工作溫度:+ 85 C 封裝 / 箱體:QFN-16 封裝:Tube |
| MAX3667E/D DIE | 制造商:Maxim Integrated Products 功能描述: |
| MAX3667ECJ | 功能描述:激光驅(qū)動器 Integrated Circuits (ICs) RoHS:否 制造商:Micrel 數(shù)據(jù)速率:4.25 Gbps 工作電源電壓:3 V to 3.6 V 電源電流:80 mA 最大工作溫度:+ 85 C 封裝 / 箱體:QFN-16 封裝:Tube |
| MAX3667ECJ+ | 功能描述:激光驅(qū)動器 Integrated Circuits (ICs) RoHS:否 制造商:Micrel 數(shù)據(jù)速率:4.25 Gbps 工作電源電壓:3 V to 3.6 V 電源電流:80 mA 最大工作溫度:+ 85 C 封裝 / 箱體:QFN-16 封裝:Tube |
| MAX3667ECJ+T | 功能描述:激光驅(qū)動器 Integrated Circuits (ICs) RoHS:否 制造商:Micrel 數(shù)據(jù)速率:4.25 Gbps 工作電源電壓:3 V to 3.6 V 電源電流:80 mA 最大工作溫度:+ 85 C 封裝 / 箱體:QFN-16 封裝:Tube |
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