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| ATA06212AD1C AGC Transimpedance Amplifier Preliminary - Rev 1 FEATURES Vdd2 Vdd2 * * * * Single +5 Volt Supply Automatic Gain Control Excellent Sensitivity (- 34 dBm) 0 dBm Optical Overload Vdd1 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 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 W ) (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 (RMS) (5) Supply Current Operating Voltage Range Operating T emperature Range + 4.5 - 40 0 30 1.0 1.0 MIN 7 3.5 400 TYP 11 5 425 300 43 1.3 1.4 40 4.2 +1 - 34 40 30 + 5.0 50 45 + 5.5 85 60 MAX UNIT k k D1 MHz Volts Volts A sec dBm dBm nA mA Volts 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. ATA06212AD1C Absolute Maximum Ratings V DD1 V DD2 IIN TA TS 7.0 V 7.0 V 5 mA Operating Temp. -40 to 125 C C Storage Temp. -65 to 150 C C ATA06212AD1C Pad Description PAD V DD1 V DD2 IIN V OUT C AGC C BY Description VDD1 VDD2 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 70kW x (4.5pF+ CAGC ) = AGC time constant >56 pF ATA06212AD1C Equivalent Ciruit VDD AGC CAGC IIN VOUT GND or neg. supply GND Photodetector cathode must be connected to IIN for proper AGC operation 2 ATA06212AD1C Bonding Pads 100um V DD2 VDD1 AN14T VDD2 GND VDD2 VDD1 Typical Bonding Diagram VDD 100um 56 pF 56 pF 925um GND V DD2 GND IIN GND VOUT PIN AN14T GND IIN GND VOUT OUT GND GND GND CBY CBY GND CAGC GND GND GND GND CBY CBY GND CAGC GND 1250um 56 pF 56 pF Note: Bond to either VDD2 Bond Pad TYPICAL CHARACTERISTICS (VDD = +5V, TA = +25C, UNLESS OTHERWISE NOTED) 3dB Bandwidth vs. Temperature CT = 0.6 pF 600.0 AGC Bandwidth vs. Temperature CT = 0.6 pF; IIN = 1.5 mA (Average) 2500.0 2400.0 2300.0 2200.0 2100.0 (MHz) VDD = 5.5V 550.0 Bandwidth (MHz) VDD = 5.5V VDD = 5.0V 500.0 VDD = 5.0V 450.0 VDD = 4.5V 400.0 350.0 -40 -20 0 20 40 60 80 100 Temperature (C) 2000.0 1900.0 1800.0 1700.0 VDD = 4.5V 1600.0 1500.0 1400.0 -40 -20 0 20 40 60 80 100 Temperature (C) Input Offset Voltage vs. Temperature 1.7 Input Referred Noise vs. Temperature CT = 0.5 pF; 467 MHz LPF 50.0 1.6 Input Referred Noise (nA RMS) VDD = 5.5V 45.0 1.5 (V) VDD = 5.0V 40.0 1.4 VDD = 4.5V 35.0 1.3 1.2 -40 -20 0 20 40 60 80 100 Temperature (C) 30.0 -40 -20 0 20 40 60 80 100 Temperature (C) 3 ATA06212AD1C 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 (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). 4 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 (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 CAGC 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. 5 ATA06212AD1C NOTES 6 ATA06212AD1C NOTES 7 ATA06212AD1C 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 discontinue any product at any time without notice. The Advanced Product data sheets and product specifications contained in this data sheet are subject to change prior to a products formal introduction. The information in this data sheet has been carefully checked and is assumed to be reliable. However, ANADIGICS assumes no responsibility 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. 8 |
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