ATA06212AD1C.pdf 데이터시트 (총 8 페이지) - 파일 다운로드 ATA06212AD1C 데이타시트 다운로드

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ATA06212AD1C
AGC Transimpedance Amplifier
Preliminary - Rev 1
FEATURES
Single +5 Volt Supply
Automatic Gain Control
Excellent Sensitivity (- 34 dBm)
0 dBm Optical Overload
Vdd2
Vdd1
Vdd2
GND
GND
I in
GND
V out
GND
GND GND CBY CBY GND CAGC GND
APPLICATIONS
SONET OC-12/SDH STM-4 Receiver
Low Noise RF Amplifier
D1
Electrical Characteristics (1)
(TA= 25°C, VDD =+5.0V + 10%, CDIODE +CSTRAY = 0.7 pF, Detector Cathode to IIN)
PARAMETER
MIN TYP MAX UNIT
Transresistance(RL=¥ ,IDC < 500 nA)
Transresistance (RL=50 W ) (1)
Bandwidth - 3dB
7 11
3.5 5
400 425
k
k
MHz
Input Resistance (2)
300
Output Resistance
30 43 60
Input Offset Voltage
Output Offset Voltage
AGC Threshold (I ) (3)
IN
AGC Time Constant (6)
Optical Overload (4)
Optical Sensitivity (7)
Input Noise Current (RMS) (5)
Supply Current
Operating Voltage Range
Operating Temperature Range
1.0 1.3
Volts NOTES
1.0 1.4
40
(1) f = 50 MHz
Volts
(2) Measured with IIN below AGC Threshold.
µA During AGC, input impedance will decrease
4.2
0 +1
proportionally to IIN.
µsec (3) Defined as the IIN where Transresistance has
dBm decreased by 50%.
(4) See note on “Indirect Measurement of Optical
- 34 dBm Overload.”
40 50 nA (5) See note on “Input Referred Noise Current.”
30
45
mA
(6) CAGC = 56 pF
(7) Parameter is guaranteed (not tested) by
+ 4.5 + 5.0 + 5.5 Volts
design and characterization data @ 622 Mb/s,
assuming detector responsively of 0.95.
- 40 85 °C

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ATA06212AD1C
Absolute Maximum Ratings
VDD1
V
DD2
IIN
T
A
TS
7.0 V
7.0 V
5 mA
Operating Temp. -40 °C to 125 °C
Storage Temp. -65 °C to 150 °C
ATA06212AD1C Pad Description
PAD Description
Comment
VDD1 VDD1
VDD2 VDD2
Positive supply for input gain stage
Positive supply for second gain stage
IIN
VOUT
CAGC
C
BY
TIA Input Current
TIA Output Voltage
External AGC Capacitor
Input gain stage bypass capacitor
Connect to detector cathode for proper operation
Requires external DC block
70kW x (4.5pF+ CAGC) = AGC time constant
>56 pF
ATA06212AD1C Equivalent Ciruit
AGC
VDD
CAGC
IIN
GND
or
neg. supply
VOUT
GND
Photodetector cathode must be connected to
IIN for proper AGC operation
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ATA06212AD1C
Bonding Pads
VDD2
VDD1
925um
AN14T
IIN
GND
100um
VDD2
100um
GND
GND
VOUT
PIN
GND GND GND CBY CBY GND CAGC GND
Typical Bonding Diagram
VDD
56 pF
56 pF
VDD2
VDD1
AN14T
IIN
GND
VDD2
GND
GND
VOUT
GND GND GND CBY CBY GND CAGC GND
OUT
1250um
56 pF
56 pF
Note: Bond to either V Bond Pad
DD2
TYPICAL CHARACTERISTICS (VDD = +5V, TA = +25°C, UNLESS OTHERWISE NOTED)
600.0
3dB Bandwidth vs. Temperature
CT = 0.6 pF
2500.0
AGC Bandwidth vs. Temperature
CT = 0.6 pF; IIN = 1.5 mA (Average)
550.0
500.0
450.0
VDD = 5.0V
VDD = 5.5V
2400.0
2300.0
2200.0
2100.0
2000.0
1900.0
1800.0
VDD = 5.5V
VDD = 5.0V
400.0
VDD = 4.5V
1700.0
1600.0
1500.0
VDD = 4.5V
350.0
-40
-20
0 20 40 60
Temperature (°C)
1400.0
80 100
-40 -20
0 20 40 60
Temperature (°C)
80
100
1.7
1.6
1.5
1.4
1.3
1.2
-40
Input Offset Voltage vs. Temperature
VDD = 5.5V
VDD = 5.0V
VDD = 4.5V
-20 0
20 40 60 80
Temperature (°C)
Input Referred Noise vs. Temperature
CT = 0.5 pF; 467 MHz LPF
50.0
45.0
40.0
35.0
30.0
100 -40
-20
0 20 40 60
Temperature (°C)
80
100
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ATA06212AD1C
POWER SUPPLIESAND GENERAL LAYOUT CONSIDERATIONS
The ATA06212AD1C may be operated from a positive supply as low as + 4.5 V and as high as + 6.0 V.
Below + 4.5 V, bandwidth, overload and sensitivity will degrade, while at + 6.0 V, bandwidth, overload
and sensitivity improve (see “Bandwidth vs. Temperature”curves). Use of surface mount (preferably
MIM type capacitors), low inductance power supply bypass capacitors (>=56pF) are essential for
good high frequency and low noise performance. The power supply bypass capacitors should be
mounted on or connected to a good low inductance ground plane.
GENERAL LAYOUT CONSIDERATIONS
Since the gain stages of the transimpedance amplifier have an open loop bandwidth in excess of 1.0
GHz, it is essential to maintain good high frequency layout practices. To prevent oscillations, a low
inductance RF ground plane should be made available for power supply bypassing. Traces that can be
made short should be made short, and the utmost care should be taken to maintain very low capacitance
at the photodiode-TIA interface (I ); excess capacitance at this node will cause a degradation in
IN
bandwidth and sensitivity.
IIN CONNECTION
Bonding the detector cathode to I (and thus drawing current from the ATA06212D1C) improves the
IN
dynamic range. Although the detector may be used in the reverse direction for input currents not
exceeding 25 µA, the specifications for optical overload will not be met (refer to the equivalent circuit
diagram).
V CONNECTION
OUT
The output pad should be connected via a coupling capacitor to the next stage of the receiver channel
(filter or decision circuits), as the output buffers are not designed to drive a DC coupled 50 Ohm load
(this would require an output bias current of approximately 36 mA to maintain a quiescent 1.8 Volts
across the output load). If VOUT is connected to a high input impedance decision circuit (>500 Ohms),
then a coupling capacitor may not be required, although caution should be exercised since DC offsets
of the photo detector/TIA combination may cause clipping of subsequent gain or decision circuits.
SENSITIVITY AND BANDWIDTH
In order to guarantee sensitivity, the TIA is subjected to a comprehensive series of tests at the die sort
level (100% testing at 25 oC) to verify the DC and AC parametric performance (transimpedance and
bandwidth).
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ATA06212AD1C
INDIRECT MEASUREMENT OF OPTICAL OVERLOAD
Optical overload can be defined as the maximum optical power above which the BER (bit error rate)
increases beyond 1 error in 1010 bits. The ATA06212AD1C is 100% tested at die sort by an AC
measurement which has excellent correlation with a PRBS optical overload measurement.
INPUT REFERRED NOISE CURRENT
The “Input Noise Current”is directly related to sensitivity . It can be defined as the output noise
voltage (V ) with no input signal, (including a 400 MHz lowpass filter at the output of the TIA) divided
OUT
by the AC transresistance.
AGC CAPACITOR
It is important to select an external AGC capacitor of high quality and appropriate size. The
ATA06212AD1C has an on-chip 70 kresistor with a shunt 4.5 pF capacitor to ground. Without
external capacitance the chip will provide an AGC time constant of 315 ns. For the best performance
in a typical 622Mb/s SONET receiver, a minimum AGC capacitor of 56pF is recommended. This will
provide the minimum amount of protection against pattern sensitivity and pulse width distortion on
repetitive data sequences during high average optical power conditions. The AGC function can be
disabled by bonding C to ground. Conservative design practices should be followed when selecting
AGC
an AGC capacitor, since unit to unit variability of the internal time constant and various data conditions
can lead to data errors if the chosen value is too small.
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