ATA01501

PRELIMINARY DATA SHEET - Rev 1.6 FEATURES · · · · · · · · Single +5 Volt Supply Automatic Gain Control -38 dBm Sensitivity 0 dBm Optical Overload 175 MHz Bandwidth SONET OC-3/SDH STM-1 (155mb/s) receiver FDDI Ethernet Fiber LAN Low Noise RF Amplifier AGC Transimpedance Amplifier SONET OC-3 ATA01501 VDD2 VDD1 GND GND 1992 APPLICATIONS 19 I IIN GND GND GND GND CBY CBY GND CAGC VOUT GND D1 Die Package PRODUCT DESCRIPTION The ANADIGICS ATA01501 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 S2 12 Pin 4 Sided SQFP Package into an output voltage. The ATA01501 offers a wide bandwidth of 175MHz and a dynamic range of 38dB. It is manufactured in a GaAs MESFET process and available in bare die form or a 12 pin SQFP package. VDD1 VDD2 AGC 19 K 70K + 4pF IIN GND or neg.supply CAGC - 45 VGA + 0.8 VOUT GND US PATENT CBY Photodector cathode must be connected to Iin for proper AGC operation IIN Figure 1: Equivalent Circuit 08/2001 2-1 ATA01501 VDD2 VDD1 12 11 10 GND GND 1992 1 2 9 8 7 19 I 925 um IIN GND GND GND GND CBY 1250 um CBY GND CAGC 3 VOUT GND 4 5 6 Figure 2: Die Bonding Pads Figure 3: Pin Layout Table 3: Pad Description PAD V DD1 V DD2 IIN VOUT C AGC C BY D escription V DD1 V DD2 TIA Input C urrent TIA Output Voltage External AGC C apaci tor C omment Posi ti ve supply for i nput gai n stage Posi ti ve supply for second gai n stage C onnect detector cathode for proper operati on Requi res external D C block 70K * C AGC = AGC ti me constant Input gai n stage bypass capaci tor >56 pF Table 2: Pin Description PIN 1 2 3 4 5 6 D ESC R IPTION NC GND IIN C BY GND C AGC PIN 7 8 9 10 11 12 D ESC R IPTION VOUT GND NC VDD GND NC 2 PRELIMINARY DATA SHEET - Rev 1.6 08/2001 ATA01501 ELECTRICAL CHARACTERISTICS Table 3: Absolute Maximum Ratings V DD1 V DD2 IIN TA TS 7.0 V 7.0 V 5 mA Operati ng Temp. - 400 C to 1250 C Storage Temp. - 650 C to 1500 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. PRELIMINARY DATA SHEET - Rev 1.6 08/2001 3 ATA01501 Table 4: Electrical Specifications (1) (TA= 25°C, VDD=+5.0V + 10%, CDIODE+CSTRAY = 0.5 pF, Det. Cathode to IIN) PAR AMETER Transresi stance (RL=¥,Idc=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. CT = 0.5 pF 0.17 Bandwidth (GHz) 0.15 0.13 V DD = 5.0 V 0.11 0.90 VDD = 5.5 V VDD = 4.5 V 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). -40 10 60 85 Temperature (O C) Figure 6: Bandwidth vs. Temperature PRELIMINARY DATA SHEET - Rev 1.6 08/2001 5 ATA01501 210 Bandwith (MHz) 200 190 180 170 160 150 1.44 VDD = 5.5 V VDD = 5.0 V VDD = 5.5 V 1.04 .84 .64 VDD = 4.5 V Rf .44 .24 VDD = 4.5 V 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 - 2.1 - 1.6 IIN - 1.1 - 0.6 50 .04 - 0.1 CT(pF) Figure 7: Bandwidth vs. CT Note: All performance curves are typical @ TA =25 oC unless otherwise noted. IIN (mA DC) Figure 9: Bandwidth vs. IIN (Refer to the equivalent circuit diagram.) Bonding the detector cathode to IIN (and thus drawing current from the ATA00501) 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. IIN Connection 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. 3.4 3.2 3.0 2.9 2.7 2.5 ( 2.4 2.2 o 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 25 22 19 16 13 10 7 4 VDD = 4 .5 V IIN VDD = 5.5 V 50 Transimpedance (K Ohm) Output Collapse Heavy AGC VDD = 5.5 V Linear Region 1 Rf IIN vOUT VDD = 4.5 V -4 -3 -2 -1 -2.1 -1.6 -1.1 -0.6 -0.1 IIN (mA DC) Figure 8: Transimpedance vs. IIN IIN (mA DC) Figure 10: VOUT vs. IIN 6 PRELIMINARY DATA SHEET - Rev 1.6 08/2001 BANDWIDTH (GHz) B(3dB) A / 2 π Rf (Cin +Ct) ≈ 1.24 VOUT (Volts) ATA01501 1.9 1.85 1.8 1.75 1.7 1.65 1.6 1.55 1.5 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 ATA00501D1C 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. Input Offset Voltage VDD = 5.5 V V = 5.0V DD VDD = 4.5V 10 Temperature oC 60 - 40 Figure 11: Input Offset Voltage vs. Temperature CBY Connection 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 30 MHz lowpass filter at the output of the TIA) divided by the AC transresistance. Measurement of Input Referred Noise Current The C BY pad must be connected via a low inductance path to a surface mount capacitor of at least 56pF (additional capacitance can be added in parallel with the 56 pF or 220 pF capacitors to improve low frequency response and noise performance). Referring to the equivalent circuit diagram and the typical bonding diagram, it is critical that the connection from CBY to the bypass capacitor use two bond wires for low inductance, since any high frequency impedance at this node will be fed back to the open loop amplifier with a resulting loss of transimpedance bandwidth. Two pads are provided for this purpose 14 Hz Rf CT 10 pA/ 50 6 2 CT=1.0pF CT =0.5pF 1 10 100 1000 - 0.1 Frequency (MHz) Sensitivity and Bandwidth Figure 12: Input Referred Noise Spectral Density Input Referred Noise in (nA RMS) Input Referred Noise Test Circuit 16 25dB 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. VDD = 4.5 V 100 MHz LPF 15 14 13 12 11 0.5pF TIA VDD =5.5V η(dBm) = 10 LOG 6500in R 80 - 40 0 40 Temperature (oC) FIgure 13: Input Referred Noise vs Temperature PRELIMINARY DATA SHEET - Rev 1.6 08/2001 7 ATA01501 AGC Capacitor It is important to select an external AGC capacitor of high quality and appropriate size. The ATA00501D1C 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 51MB/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. 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. 180 Degrees 200 220 240 VOUT 00501 IIN 0.5pF 50 100 150 Frequency (MHz) Figure 14: Phase (IIN to VOUT) 8 PRELIMINARY DATA SHEET - Rev 1.6 08/2001 ATA01501 PACKAGE OUTLINE 0.245 (6.22) 0.230 (5.84) 0.165 (4.19) 0.152 (3.86) 0.047 (1.19) 0.032 (0.81) 0.065 (1.65) 0.055 (1.40) 7° o 0 0.035 (.89) 0.020 (.51) 12 11 10 0.018 (.460) 0.012 (.300) 1 2 3 9 8 7 0.021X45° 4 Sides 0.000 (0.00) 0.020 (.51) 4 5 6 0.024 (.61) 0.018 (.46) 4X 0.023X45° 0.011 (.28) 0.007 (.18) 0.015 (.38) 0.000 (0.00) 0.032 BSC (0.81) Figure 15: SQFP Package Outline PRELIMINARY DATA SHEET - Rev 1.6 08/2001 9 ATA01501 NOTES 10 PRELIMINARY DATA SHEET - Rev 1.6 08/2001 ATA01501 NOTES PRELIMINARY DATA SHEET - Rev 1.6 08/2001 11 ATA01501 ORDERING INFORMATION PAR T N U MB ER ATA01501D 1C ATA01501S2C PAC K AGE OPTION D 1C S 2C PAC K AGE D ESC R IPTION Die 12 Pi n 4 Si ded SQFP Package ANADIGICS, Inc. 141 Mount Bethel Road Warren, New Jersey 07059, U.S.A. Tel: +1 (908) 668-5000 Fax: +1 (908) 668-5132 URL: http://www.anadigics.com E-mail: 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. 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. WARNING 12 PRELIMINARY DATA SHEET - Rev 1.6 08/2001