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ATA06212A
AGC Transimpedance Amplifier
PRELIMINARY DATA SHEET- Rev 1.2
FEATURES * Single +5 Volt Supply * Automatic Gain Control * - 34 dBm Sensitivity * 0 dBm Optical Overload * 425 MHz Bandwidth APPLICATIONS * SONET OC-12/SDH STM-4 (622 Mb/s) *
Receiver Low Noise RF Amplifier
Vdd2
Vdd2
Vdd1
GND
GND
I in
GND
V out
GND
GND
GND
CBY
CBY
GND
CAGC
GND
D1
PRODUCT DESCRIPTION
The ANADIGICS ATA06212A is a 5V low noise transimpedance amplifier with AGC designed to be used in OC-12/STM-4 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 ATA06212A offers a bandwidth of 425MHz and a dynamic range of 35dB. It is manufactured in a GaAs MESFET process and is available in bare die form.
VDD AGC
VOUT
IIN
GND
GND or neg. supply
Photodetector cathode must be connected to IIN for proper AGC operation
Figure 1: Equivalent Circuit
08/2001
ATA06212A
100um VDD2 VDD1 AN14T VDD2 GND 100um
925um
GND
IIN GND VOUT
GND
GND
GND
CBY
CBY
GND
CAGC
GND
1250um
Figure 2: Bonding Pad Table 1: ATA06212AD1C Pad Description
PAD V DD1 VDD2 IIN VOUT CAGC C BY DESCRIPTION VD D 1 VD D 2 TIA Input Current TIA Output Voltage External AGC Capacitor Input gain stage bypass capacitor COMMENT Positive supply for input gain stage Positive supply for second gain stage Connect to detector cathode for proper operation Requires external DC block 70k x (4.5pF+ CAGC) = AGC time constant >56 pF
ELECTRICAL CHARACTERISTICS
Table 2: Absolute Maximum Ratings
VDD1 VDD2 IIN TA TS 7.0 V 7.0 V 5 mA Operating Temp. -40 C to 125 C Storage Temp. -65 C to 150 C
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 1.2 08/2001
ATA06212A Table 3: Electrical Characteristics (1) (TA= 25C, VDD =+5.0V + 10%, CDIODE +CSTRAY = 0.7 pF, Detector Cathode to IIN)
PARAMETER Transresistance(RL=,IDC < 500 nA) Transresistance (RL=50 ) (1) Bandwidth - 3dB Input Resistance (2) Output Resistance Input Offset Voltage Output Offset Voltage AGC Threshold (IIN) (3) AGC Time Constant (6) Optical Overload (4) Optical Sensitivity (7) Input Noise Current (5) Supply Current Operating Voltage Range Operating Temperature Range MIN 7 3.5 400 30 1.0 1.0 0 + 4.5 - 40 TYP 11 5 425 300 43 1.3 1.4 40 4.2 +1 - 34 40 30 + 5.0 MAX 60 50 45 + 6.0 85 UNIT K K MHz

Volts Volts
A sec
dB m dB m nA mA Volts
o
C
Notes: (1) f = 50 MHz (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 "Input Referred Noise Current." (6) CAGC = 56 pF (7) Parameter is guaranteed (not tested) by design and characterization data @ 622 Mb/s, assuming detector responsively of 0.95.
PRELIMINARY DATA SHEET - Rev 1.2 08/2001
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ATA06212A
VDD
56 pF
56 pF
VDD2 VDD1 AN14T PIN
VDD2 GND
GND
IIN GND VOUT
OUT
GND
GND
GND
CBY
CBY
GND
CAGC
GND
56 pF
56 pF
Note: Bond to either VDD2 Bond Pad
Figure 3: Typical Bonding Diagram
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PRELIMINARY DATA SHEET - Rev 1.2 08/2001
ATA06212A
PERFORMANCE DATA (VDD = +5V, TA = +25C, UNLESS OTHERWISE NOTED)
Figure 4: 3dB Bandwidth vs. Temperature
CT = 0.6 pF
600.0
Figure 5: AGC Bandwidth vs. Temperature
CT = 0.6 pF; IIN = 1.5 mA (Average)
2500.0 2400.0 2300.0 2200.0 2100.0 (MHz) 2000.0 1900.0 1800.0 1700.0 1600.0 1500.0 1400.0 -40
VDD = 5.5V
550.0 Bandwidth (MHz)
VDD = 5.5V
VDD = 5.0V
500.0
VDD = 5.0V
450.0
VDD = 4.5V
VDD = 4.5V
400.0
350.0 -40 -20 0 20 40 60 80 100 Temperature (C)
-20
0
20
40
60
80
100
Temperature (C)
Figure 6: Input Offset Voltage vs. Temperature
Figure 7: Input Referred Noise vs. Temperature
CT = 0.5 pF; 467 MHz LPF
1.7
VDD = 5.5V
50.0 Input Referred Noise (nA RMS
1.6
45.0
1.5 (V)
VDD = 5.0V
40.0
1.4
VDD = 4.5V
35.0
1.3
30.0
1.2 -40 -20 0 20 40 60 80 100 Temperature (C)
-40
-20
0
20
40
60
80
100
Temperature (C)
PRELIMINARY DATA SHEET - Rev 1.2 08/2001
5
ATA06212A
APPLICATION INFORMATION
POWER SUPPLIES AND 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 (IIN); excess capacitance at this node will cause a degradation in bandwidth and sensitivity. IIN CONNECTION Bonding the detector cathode to IIN (and thus drawing current from the ATA06212D1C) improves the dynamic range. Although the detector may be used in the reverse direction for input currents not exceeding 25 A, the specifications for optical overload will not be met (refer to the equivalent circuit diagram). VOUT CONNECTION The output pad should be connected via a coupling capacitor to the next stage of the receiver channel
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). 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 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 (VOUT) with no input signal, (including a 400 MHz lowpass filter at the output of the TIA) divided 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 k resistor 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 AGC to ground. 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.
(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
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PRELIMINARY DATA SHEET - Rev 1.2 08/2001
ATA06212A
NOTES
PRELIMINARY DATA SHEET - Rev 1.2 08/2001
7
ATA06212A
ORDERING INFORMATION
PART NUMBER ATA06212AD1C PACKAGE OPTION D 1C PACKAGE DESCRIPTION Die
ANADIGICS, Inc. 35 Technology Drive Warren, New Jersey 07059 Tel: (908) 668-5000 Fax: (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 1.2 08-2001

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