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PDF MAX3665 Data sheet ( Hoja de datos )
| Número de pieza | MAX3665 | |
| Descripción | 622Mbps / Ultra-Low-Power / 3.3V Transimpedance Preamplifier for SDH/SONET | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX3665 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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19-1601; Rev 0; 1/00
EVAALVUAAILTAIOBNLEKIT
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
________________General Description
The MAX3665 low-power transimpedance preamplifier
for 622Mbps SDH/SONET applications consumes only
70mW at VCC = 3.3V. Operating from a single +3.3V or
+5.0V supply, it converts a small photodiode current to a
measurable differential voltage. A DC cancellation circuit
provides a true differential output swing over a wide
range of input current levels, thus reducing pulse-width
distortion. The differential outputs are back-terminated
with 50Ω per side.
The overall transimpedance gain is nominally 8kΩ. For
input signal levels beyond approximately 50µAp-p, the
amplifier will limit the output swing to 250mV. The
MAX3665’s low 55nA input noise provides a typical
sensitivity of -33.2dBm in 1300nm, 622Mbps receivers.
The MAX3665 is designed to be used in conjunction
with the MAX3676 clock recovery and data retiming IC
with limiting amplifier. Together they form a complete
3.3V or 5.0V 622Mbps SDH/SONET receiver.
In die form, the MAX3665 is designed to fit on a header
with a PIN diode. It includes a filter connection that pro-
vides positive bias for the photodiode through a 1.5kΩ
resistor to VCC. The device is available in an 8-pin
µMAX package.
____________________________Features
o +3.3V or +5.0V Single-Supply Operation
o 55nARMS Input-Referred Noise
o 70mW Power Consumption at VCC = 3.3V
o 8kΩ Gain
o 450µA Peak Input Current
o 260ps max Deterministic Jitter
o Differential Output Drives 100Ω Load
o 470MHz Bandwidth
_______________Ordering Information
PART
MAX3665EUA
MAX3665E/D
TEMP. RANGE
-40°C to +85°C
(see Note)
PIN-PACKAGE
8 µMAX
Dice
Note: Dice are designed to operate over a -40°C to +140°C
junction temperature (Tj) range, but are tested and guaranteed
at TA = +25°C.
________________________Applications Pin Configuration appears at end of data sheet.
SDH/SONET Receivers
PIN Photodiode Preamplifiers and Receivers
Regenerators for SDH/SONET
__________________________________________________Typical Application Circuit
3.3V
0.01µF
RFILT
VCC
1.5k MAX3665
CFILT
FILT
IN
OUT+
50Ω
50Ω
OUT-
GND
0.1µF
0.1µF
3.3V
LIMITING
AMP
MAX3676
CLOCK
AND
DATA
RECOVERY
CLK
DATA
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
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 100Ω
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 (CFILT) between
FILT and case ground for TO header, die-mounted oper-
ation. Increasing CFILT 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 8kΩ 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 = PAVG = (P0 + P1) / 2
Extinction Ratio = re = P1 / P0
Peak-to-Peak Signal Amplitude = Pp-p = P1 - P0
POWER
P1
PAVG
P0
Figure 2. Optical Power Definitions
TIME
_______________________________________________________________________________________ 5
5 Page 
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
NOTES
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX3665.PDF ] | |
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