ANADIGICS ATA01504D1C

ATA01504
AGC Transimpedance Amplifier
SONET OC-3
PRELIMINARY DATA SHEET-Rev 1
FEATURES
·
Single +5 Volt Supply
·
TO Package Compatible
·
Automatic Gain Control
·
-38 dBM Sensitivity
·
0 dBm Overload
·
175 MHz Bandwidth
APPLICATIONS
·
SONET OC-3/SDH STM-1 (155 Mb/s) Receiver
·
FDDI, Ethernet Fiber LAN
·
Low Noise RF Amplifier
D1C
PRODUCT DESCRIPTION
The ANADIGICS ATA01504 is a 5V low noise
transimpedance amplifier with AGC designed to be
used in OC-3/STM-1 fiber optic links. The device is
used in conjunction with a photodetector (PIN diode
or avalanche photodiode) to convert an optical signal
into an output voltage. The ATA01504 offers a
bandwidth of 175MHz, a dynamic range of 38dB and
an alternate pad layout as compared to the ATA01501.
It is manufactured in a GaAs MESFET process and
is available in bare die form.
VDD
AGC
19K
70K
CAGC
+
IIN
4.5 pF
- 45
VGA
+ 0.8
GND
or
neg.supply
VOUT
GND
US PATENT
5442321,5602510,5047728
Photodector cathode must be connected
to IIN for proper AGC operation
Figure 1: Equivalent Circuit
08/2001
ATA01504
Figure 2: Bonding Pad Layout
Table 1: Pad Description
PAD
D escription
C omment
V DD
V DD
Posi ti ve supply for i nput gai n stage
TIA Input C urrent
C onnect detector cathode for proper operati on
VOUT
TIA Output Voltage
Requi res external D C block
C AGC
External AGC C apaci tor
70K* (C AGC *4.5 pF) = AGC Ti me C onstant
IIN
ELECTRICAL CHARACTERISTICS
Table 2: Absolute Maximum Ratings
V DD
7.0 V
IIN
5 mA
TA
Operati ng Temp. - 40 oC to 125 oC
TS
Storage Temp. - 65 oC to 150 oC
Stresses in excess of the absolute ratings may cause
permanent damage. Functional operation is not implied
under these conditions. Exposure to absolute ratings
for extended periods of time may adversely affect
reliability.
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PRELIMINARY DATA SHEET - Rev 1
08/2001
ATA01504
Table 3: Electrical Specifications (1)
(TA = 25°C, VDD =+5.0V + 10%, CDIODE + CSTRAY = 0.5 pF, Det. cathode to IIN)
PAR AMETER
MIN
Transresi stance (RL=¥,IDC<500nA)
Transresi stance (RL=50 W )
(1)
Bandwi dth -3dB
5.5
150
30
Supply C urrent
Input Offset Voltage
1.5
Output Offset Voltage
8
15
Opti cal Overload
-3
U N IT
KW
10
KW
175
MHz
500
W
50
60
W
30
45
mA
1.6
1.9
1.8
AGC Threshold (IIN) (3)
(4)
MAX
17
Input Resi stance (2)
Output Resi stance
TYP
Volts
Volts
mA
30
0
dB m
Input Noi se C urrent (5)
14
AGC Ti me C onstant
16
m se c
1
mV/ º C
(6)
Offset Voltage D ri ft
Opti cal Sensi ti vi ty
20
-38
(7)
Operati ng Voltage Range
+ 4.5
Operati ng Temperature Range
- 40
+ 5.0
nA
dB m
+ 6.0
Volts
85
ºC
Notes:
1. f = 50MHz
2. Measured with Iin below AGC Threshold. During AGC, input impedance will
decrease proportionally to Iin.
3. Defined as the Iin where Transresistance has decreased by 50%.
4. See note on “Indirect Measurement of Optical Overload.”
5. See note on “Measurement of Input Referred Noise Current.”
6. CAGC = 220 pF
7. Parameter is guaranteed (not tested) by design and characterization data
@155 Mb/s, assuming dectector responsivity of 0.9.
PRELIMINARY DATA SHEET - Rev 1
08/2001
3
ATA01504
APPLICATION INFORMATION
V
CAGC
Figure 3: ATA 01504D1C Typical Bonding Diagram
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 (IIN), as
excess capacitance at this node will cause a
degradation in bandwidth and sensitivity (see
Bandwidth vs. CT curves).
4
210
B(3dB) A
≈ / 2 π Rf (Cin +Ct)
200
Bandwith (MHz)
Power supplies and general layout considerations
The ATA01504D1C 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. 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.
VDD = 5.5 V
190
VDD = 5.0 V
180
170
160
VDD = 4.5 V
150
0 0.2 0.4 0.6 0.8
1
1.2
1.4 1.6
CT(pF)
Figure 4: Bandwidth vs. CT
Note: All performance curves are typical @ TA =25 °C
unless otherwise noted.
PRELIMINARY DATA SHEET - Rev 1
08/2001
ATA01504
9
8
7
I
6
IIN
50
5
4
VDD = 5.5 V
3
2
VDD = 4.5 V
-2.1
- 1.6
-1.1
- 0.6
- 0.1
Transimpedance (K Ohm)
10
VOUT Connection
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.
heavy AGC
Output Collapse
VDD =5.5 V
Linear Region
Rf
1
I IN
VOUT
IIN (mA DC)
VDD = 4.5 V
Figure 5: Transimpedance vs. IIN
Bandwidth vs IIN
-4
1.1
0.9
0.7
VDD=4.5 V
0.5
1501
50 0.3
0.1
- 2.1
- 1.6
- 1.1
- 0.6
IIN (mA DC)
- 0.1
BANDWIDTH (GHz)
VDD=5.5 V
-2
-1
IIN (mA DC)
1.5
1.3
IIN
-3
3.4
3.2
3.0
2.9
2.7
2.5
2.4
2.2
2.0
1.9
1.7
1.5
1.4
1.2
1.0
0.8
0.7
0.5
0.3
0.2
0.0
VOUT(Volts)
IIN connection
(refer to the equivalent circuit diagram) Bonding the
detector cathode to IIN (and thus drawing current from
the ATA01504) improves the dynamic range. Although
the detector may be used in the reverse direction for
input currents not exceeding 25 mA, the specifications
for optical overload will not be met.
Figure 7: VOUT vs. IIN
Sensitivity and Bandwidth
In order to guarantee sensitivity and bandwidth
performance, the TIA is subjected to a
comprehensive series of tests at the die sort level
(100% testing at 25 oC) to verify the DC parametric
performance and the high frequency performance
(i.e. adequate |S21|) of the amplifier. Acceptably high
|S21| of the internal gain stages will ensure low
amplifier input capacitance and hence low input
referred noise current. Transimpedance sensitivity
and bandwidth are then guaranteed by design and
correlation with RF and DC die sort test results.
Figure 6: Bandwidth vs. IIN
PRELIMINARY DATA SHEET - Rev 1
08/2001
5
ATA01504
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 10 10 bits. The
ATA01504D1C is 100% tested at die sort by a DC
measurement which has excellent correlation with
an PRBS optical overload measurement. The
measurement consists of sinking a negative current
(see VOUT Vs IIN figure) from the TIA and determining
the point of output voltage collapse. Also the input
node virtual ground during “heavy AGC” is checked
to verify that the linearity (i.e. pulse width distortion)
of the amplifier has not been compromised.
Phase response
At frequencies below the 3dB bandwidth of the device,
the transimpedance phase response is
characteristic of a single pole transfer function (as
shown in the Phase Vs Frequency curve). The output
impedance is essentially resistive up to 1000 MHz.
Measurement of Input Referred Noise Current
The “Input Noise Current” is directly related to
sensitivity . It can be defined as the output noise
voltage (Vout), with no input signal, (including a 110
MHz lowpass filter at the output of the TIA) divided by
the AC transresistance.
14
Hz
Rf
10
pA/
CT
6
Figure 9: Phase (IIN to VOUT)
50
CT=1.0pF
2
- 0.1
CT =0.5pF
1
10
100
1000
Frequency (MHz)
Figure 8: Input Referred Noise Spectral Density
AGC Capacitor
It is important to select an external AGC capacitor of
high quality and appropriate size. The ATA01504D1C
has an on-chip 70 KW resistor with a shunt 4 pF
capacitor to ground. Without external capacitance the
chip will provide an AGC time constant of 280 nS. For
the best performance in a typical 155 MB/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.
Conservative design practices should be followed
when selecting 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.
6
PRELIMINARY DATA SHEET - Rev 1
08/2001
ATA01504
NOTES
PRELIMINARY DATA SHEET - Rev 1
08/2001
7
ATA01504
ORDERING INFORMATION
PAR T N U MB ER
PAC K AGE OPTION
PAC K AGE D ESC R IPTION
ATA01504D 1C
D 1C
Die
ANADIGICS, Inc.
141 Mount Bethel Road
Warren, New Jersey 07059, U.S.A
Tel: +1 (908) 668-5000
Fax: +1 (908) 668-5132
http://www.anadigics.com
Mktg@anadigics.com
IMPORTANT NOTICE
ANADIGICS, Inc. reserves the right to make changes to its products or to discontinue any product at any time without
notice. The product specifications contained in Advanced Product Information sheets and Preliminary Data Sheets are
subject to change prior to a product’s formal introduction. Information in Data Sheets have been carefully checked and are
assumed to be reliable; however, ANADIGICS assumes no responsibilities for inaccuracies. ANADIGICS strongly urges
customers to verify that the information they are using is current before placing orders.
WARNING
ANADIGICS products are not intended for use in life support appliances, devices, or systems. Use of an ANADIGICS
product in any such application without written consent is prohibited.
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PRELIMINARY DATA SHEET - Rev 1
08/2001