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參數(shù)資料
| 型號： | MAX3969 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 2x2 Crosspoint Switch : LVDS Outputs 16-SOIC -40 to 85 |
| 中文描述： | 200Mbps SFP限幅放大器 |
| 文件頁數(shù)： | 6/11頁 |
| 文件大?。?/td> | 724K |
| 代理商： | MAX3969 |
M
Power Detector
Each amplifier stage contains a logarithmic FWD, which
indicates the RMS input signal power. The FWD outputs
are summed together at the FILTER pin where the sig-
nal is filtered by an external capacitor (C
FILTER
) con-
nected between FILTER and V
CC
. The FILTER signal
generates the RSSI output voltage (V
RSSI
), which is
proportional to the input power in decibels. When LOS
is low, V
RSSI
is approximated by the following equation:
V
RSSI
(V) = 1.2V + 0.5log (V
IN
)
where, V
IN
is the data input voltage measured in mV
P-P
.
This relation translates to a 25mV increase in V
RSSI
for
every 1dB increase in V
IN
. The RSSI output is reduced
approximately 120mV when LOS is high.
Typically the RSSI output is connected to an A/D con-
verter for diagnostic monitoring. This output can be left
open if not required in the application. The RSSI output
is designed to drive a minimum load resistance of 10k
to ground, and a maximum capacitance of 10pF. A
10k
series resistor is required to buffer loads greater
than 10pF.
Signal-Strength Comparator
A comparator is used to indicate the input signal
strength relative to a user-programmable threshold.
One of the comparator inputs is connected to the RSSI
output signal, and the other is connected to the thresh-
old voltage (V
TH
), which is set externally and provides
a trip point for signal-strength indication. When the sig-
nal strength is above the threshold, the SD output
asserts high and the LOS output deasserts low.
Likewise, when the signal strength falls below the
threshold, SD deasserts low and LOS asserts high. To
ensure chatter-free operation, the comparator is
designed with approximately 5dB of hysteresis.
Squelch
The squelch function disables the data outputs by forc-
ing OUT- low and OUT+ high when the input signal is
below the programmed threshold. This function
ensures that when there is a loss of signal, the limiting
amplifier and all downstream devices do not respond to
input noise. Connect SQUELCH to GND or leave it
unconnected to disable squelch. Connect SQUELCH to
V
CC
to enable squelch.
PECL Outputs
The data outputs (OUT+, OUT-) and signal-detect out-
put (SD) are supply-referenced PECL outputs. See
Figure 2 for the equivalent output circuit.
Both data outputs must be terminated for proper opera-
tion, but the SD output can be left open if not required
in the application. The proper termination for a PECL
output is 50
to (V
CC
- 2V), but other standard termina-
tion techniques can be used. For more information on
PECL terminations and how to interface with other logic
families, refer to Maxim Application Note
HFAN-01.0:
Introduction to LVDS, PECL, and CML.
TTL Outputs
The LOS outputs (LOS,
LOS
) are implemented with
open-collector, Schottky-clamped, ESD-protected, TTL-
compatible outputs. See Figure 3 for the equivalent out-
put circuit. The LOS outputs require external pullup
resistors for proper operation. Resistor values between
4.7k
and 10k
are recommended.
If the LOS outputs are not required for the application,
they can be left open.
Design Procedure
Program the Power-Detect Threshold
The suggested procedure for setting the power-detect
threshold is given below and is illustrated in Figure 4.
1) Determine the maximum receiver sensitivity
(RX_MAX) in dBm and the PIN-TIA responsivity (G)
in V/W.
2) Calculate the differential voltage swing (VIN_SEN) at
the MAX3969 inputs while operating at sensitivity.
V
IN_SEN
= 10
(RX_MAX / 10)
x 2 x G
3) Calculate the threshold voltage (V
IN_TH
) at which
LOS must be low (SD must be high) by allowing
3.6dB (1.8dB optical) margin for power-detector
accuracy.
V
IN_TH
= V
IN_SEN
x 0.66
4) Use V
IN_TH
and the line labeled (SD HIGH / LOS
LOW) in the Power-Detect Threshold vs. R2 graph
in the
Typical Operating Characteristics
to deter-
mine the value of R2. Select R1=100k
.
200Mbps SFP Limiting Amplifier
6
_______________________________________________________________________________________
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX3969E/D | 功能描述:限幅放大器 RoHS:否 制造商:Micrel 輸入電壓范圍（最大值）:3.6 V 工作電源電壓:3.3 V 電源電流:40 mA 工作溫度范圍:- 40 C to + 85 C 封裝 / 箱體:MSOP-10 封裝:Tube |
| MAX3969E/D DIE | 制造商:Maxim Integrated Products 功能描述: |
| MAX3969E/D+ | 功能描述:限幅放大器 RoHS:否 制造商:Micrel 輸入電壓范圍（最大值）:3.6 V 工作電源電壓:3.3 V 電源電流:40 mA 工作溫度范圍:- 40 C to + 85 C 封裝 / 箱體:MSOP-10 封裝:Tube |
| MAX3969ETP | 功能描述:限幅放大器 270Mbps SFP LED RoHS:否 制造商:Micrel 輸入電壓范圍（最大值）:3.6 V 工作電源電壓:3.3 V 電源電流:40 mA 工作溫度范圍:- 40 C to + 85 C 封裝 / 箱體:MSOP-10 封裝:Tube |
| MAX3969ETP+ | 功能描述:限幅放大器 270Mbps SFP LED RoHS:否 制造商:Micrel 輸入電壓范圍（最大值）:3.6 V 工作電源電壓:3.3 V 電源電流:40 mA 工作溫度范圍:- 40 C to + 85 C 封裝 / 箱體:MSOP-10 封裝:Tube |
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