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參數(shù)資料
| 型號(hào)： | MAX3665EUA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 數(shù)字傳輸電路 |
| 英文描述： | 622Mbps, Ultra-Low-Power, 3.3V Transimpedance Preamplifier for SDH/SONET |
| 中文描述： | ATM/SONET/SDH SUPPORT CIRCUIT, PDSO8 |
| 封裝： | MO-187C-AA, MICRO MAX PACKAGE-8 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 584K |
| 代理商： | MAX3665EUA |
M
Therefore,
P
AVG
= Pp-p (1 / 2)[(r
e
+ 1) / (r
e
- 1)]
Sensitivity is a key specification of the receiver module.
The ITU/Bellcore specifications for SDH/SONET
receivers require a link sensitivity of -27dBm with a bit
error rate (BER) of 10
-10
. There is an additional 1dB
power penalty to accommodate various system losses;
therefore, the sensitivity of a 622Mbps receiver must be
better than -28dBm.
Although several parameters affect sensitivity (such as
the quantizer sensitivity and preamplifier gain, as previ-
ously discussed), most fiber optic receivers are designed
so that noise is the dominant factor. Noise from the high-
gain transimpedance amplifier, in particular, determines
the sensitivity. The noise generated by the MAX3665 can
be modeled with a Gaussian distribution. In this case, a
BER of 10
-10
corresponds to a peak-to-peak signal
amplitude to RMS noise ratio (SNR) of 12.7. The
MAX3665’s typical input-referred noise, i
n
, (bandwidth-
limited to 470MHz) is 55nA
RMS
. Therefore, the minimum
input for a BER of 10
-10
is (12.7
·
55nA) = 699nAp-p.
Rearranging the previous equations in these terms
results in the following relationship:
Optical Sensitivity (dBm) =
10log[(i
n
/
ρ
)(SNR)(1/2)(r
e
+ 1) / (r
e
- 1)(1000)]
At room temperature, with r
e
= 10, SNR = 12.7, i
n
=
55nA, and
ρ
= 0.9A/W, the MAX3665 sensitivity is
-33.2dBm. For worst-case conditions, noise increases
to 72nA and sensitivity decreases to -32.1dBm. The
MAX3665 provides 5.1dB margin over the SDH/SONET
specifications, even at +85°C.
The MAX3665’s overload current (I
MAX
) is greater than
450μAp-p. The pulse-width distortion and input current
are closely related. If the clock recovery circuit can
accept more pulse-width distortion, a higher input current
might be acceptable. For worst-case responsivity and
extinction ratio,
ρ
= 1A/W and r
e
=
∞
, the input overload
is:
Overload (dBm) = -10log (I
MAX
)(1 / 2)(1000)
For I
MAX
= 450μA, the MAX3665 overload is -6.5dBm.
Step 2: Designing Filters
The MAX3665’s noise performance is a strong function
of the circuit’s bandwidth, which changes over temper-
ature and varies from lot to lot. The receiver sensitivity
can be improved by adding filters to limit this band-
width. Filter designs can range from a one-pole filter
using a single capacitor, to more complex filters using
inductors. Figure 3 illustrates two examples: the simple
filter provides moderate roll-off with minimal compo-
nents, while the complex filter provides a sharper roll-
off. Parasitics on the PC board will affect the filter char-
acteristics. Refer to the MAX3665 EV kit data sheet for a
layout example of the filter shown in Figure 3b.
Supply voltage noise at the cathode of the photodiode
produces a current I = C
PHOTO
(
V/
t), which reduces
the receiver sensitivity. C
PHOTO
is the photodiode
capacitance.
The FILT resistor of the MAX3665, combined with an
external capacitor (see
Typical Operating Circuit
) can
be used to reduce this noise. The external capacitor
(C
FILT
) is placed in parallel with the photodiode.
Current generated by supply noise is divided between
C
FILT
and C
PHOTO
. The input noise current due to sup-
ply noise is (assuming the filter capacitor is much larger
than the photodiode capacitance):
I
V
C
C
)(
R
(
NOISE
NOISE
PHOTO
FILT
FILT
=
(
)(
)
)
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
6
_______________________________________________________________________________________
MAX3665
C1
5pF
22nH
22nH
R
L
100
a)
SIMPLE, 1-POLE, 530MHz FILTER
50
50
1.2pF
MAX3665
4pF
5pF
R
L
100
b)
3-POLE, 515MHz FILTER
50
50
1.2pF
REFER TO THE MAX3665 EV KIT DATA SHEET
FOR THE FILTER LAYOUT EXAMPLE.
Figure 3. Filter Design Examples
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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 |
| 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 |
| MAX3665EVKIT | 制造商:Maxim Integrated Products 功能描述:Amplifier IC Development Tools MAX3665EVKIT |
| MAX3667E/D | 功能描述:激光驅(qū)動(dòng)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 |
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