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參數(shù)資料
| 型號(hào)： | MAX3665 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Single LVDS Transmitter 5-SOT-23 -40 to 85 |
| 中文描述： | 622Mbps、超低功耗，3.3V互阻前置放大器，用于SDH/SONET |
| 文件頁數(shù)： | 5/12頁 |
| 文件大小： | 584K |
| 代理商： | MAX3665 |
Paraphase Amplifier
The paraphase amplifier converts single-ended inputs to
differential outputs, and introduces a voltage gain. This
signal drives a differential pair of transistors, Q2 and Q3,
which form the output stage. Resistors R1 and R2 provide
back-termination at the output, absorbing reflections
between the MAX3665 and its load.
The differential outputs are designed to drive a 100
load between OUT+ and OUT-. They can also drive
higher output impedances, resulting in increased gain
and output voltage swing.
DC Cancellation Loop
The DC cancellation loop removes the DC component
of the input signal by using low-frequency feedback.
This feature centers the signal within the MAX3665’s
dynamic range, reducing pulse-width distortion on
large input signals.
The output of the transimpedance amplifier is sensed
through resistors R3 and R4 and then filtered, amplified,
and fed back to the base of transistor Q4. The transistor
draws the DC component of the input signal away from
the transimpedance amplifier’s summing node.
Connect a 400pF or larger capacitor (C
FILT
) between
FILT and case ground for TO header, die-mounted oper-
ation. Increasing C
FILT
improves PSRR. The DC cancel-
lation loop can sink up to 300μA of current at the input.
The MAX3665 minimizes pulse-width distortion for data
sequences that exhibit a 50% mark density. A mark
density other than 50% causes the device to generate
pulse-width distortion.
DC cancellation current is drawn from the input and
adds noise. For low-level signals with little or no DC
component, this is not a problem. Preamplifier noise will
increase for signals with a significant DC component.
___________Applications Information
The MAX3665 is a low-noise, wide-bandwidth transim-
pedance amplifier that is ideal for 622Mbps SDH/
SONET receivers. Its features allow easy design into a
fiber optic module, in three simple steps.
Step 1: Selecting a Preamplifier for a 622Mbps
Receiver
Fiber optic systems place requirements on the band-
width, gain, and noise of the transimpedance preampli-
fier. The MAX3665 optimizes these characteristics for
SDH/SONET receiver applications that operate at
622Mbps.
In general, the bandwidth of a fiber optic preamplifier
should be 0.6 to 1 times the data rate. Therefore, in a
622Mbps system, the bandwidth should be between
375MHz and 622MHz. Lower bandwidth causes pat-
tern-dependent jitter and a lower signal-to-noise ratio,
while higher bandwidth increases thermal noise. The
MAX3665 typical bandwidth is 470MHz, making it ideal
for 622Mbps applications.
The preamplifier’s transimpedance must be high
enough to ensure that expected input signals generate
output levels exceeding the sensitivity of the limiting
amplifier (quantizer) in the following stage. The
MAX3676 clock recovery and limiting amplifier IC has an
input sensitivity of 3.6mVp-p, which means that
3.6mVp-p is the minimum signal amplitude required to
produce a fully limited output. Therefore, when used
with the MAX3665, which has an 8k
transimpedance,
the minimum detectable photodetector current is
450nAp-p.
It is common to relate peak-to-peak input signals to
average optical power. The relationship between opti-
cal input power and output current for a photodetector
is called the responsivity (
ρ
), with units amperes per
watt (A/W). The photodetector peak-to-peak current is
related to the peak-to-peak optical power as follows:
Ip-p = (Pp-p)(
ρ
)
Based on the assumption that SDH/SONET signals
maintain a 50% mark density, the following equations
relate peak-to-peak optical power to average optical
power and extinction ratio (Figure 2):
Average Optical Power = P
AVG
= (P0 + P1) / 2
Extinction Ratio = r
e
= P1 / P0
Peak-to-Peak Signal Amplitude = Pp-p = P1 - P0
M
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
_______________________________________________________________________________________
5
POWER
TIME
P0
P1
P
AVG
Figure 2. Optical Power Definitions
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX3665EUA | 622Mbps, Ultra-Low-Power, 3.3V Transimpedance Preamplifier for SDH/SONET |
| MAX3667ECJ | +3.3V, 622Mbps SDH/SONET Laser Driver with Automatic Power Control |
| MAX3667 | Single LVDS Transmitter 5-SOT-23 -40 to 85 |
| MAX3668 | Single LVDS Transmitter 8-SOIC -40 to 85 |
| MAX3668EHJ | +3.3V, 622Mbps SDH/SONET Laser Driver with Automatic Power Control |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX3665E/D | 制造商:Maxim Integrated Products 功能描述:622MBPS, ULTRA-LOW-POWER, 3.3V TRANSIMPEDANCE - Gel-pak, waffle pack, wafer, diced wafer on film 制造商:Maxim Integrated Products 功能描述:622MBPS ULTRA-LOW-POWER 3.3V TRANSIMPEDA |
| MAX3665E/D-B3D | 制造商:Maxim Integrated Products 功能描述:622MBPS,ULTRA-LOW-POWER,3.3V TRANSIMPEDANCEPREAMPLIFIER - Bulk |
| MAX3665EUA | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
| MAX3665EUA+ | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
| MAX3665EUA+T | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
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