ATA00501S2C

PRELIMINARY DATA SHEET-Rev 1.5 FEATURES · · · · · Single +5 Volt Supply Automatic Gain Control -43 dBm Sensitivity 0 dBm Optical Overload 70 MHz Bandwidth VDD1 AGC Transimpedance Amplifier SONET OC-1 ATA00501 VDD2 GND GND 1992 APPLICATIONS · · · OC-1 Receiver FITL Low Noise RF Amplifier 19F IIN GND GND GND GND CBY CBY VOUT GND CAGC GND D1C S2 12 Pin 4 Sided SQFP Package PRODUCT DESCRIPTION The ANADIGICS ATA00501 is a 5V low noise transimpedance amplifier with AGC designed to be used in OC-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 ATA00501 has a bandwidth of 70MHz and a dynamic range in excess of 40dB. It is manufactured in a GaAs MESFET process and available in bare die form or a 12 pin SQFP package. VDD AGC 70K 60K IIN GND or neg.supply + 4pF CAGC - 35 VGA + 0.8 VOUT GND 20pF PATENT PENDING CBY Photodetector cathode must be connected To IIN for proper AGC operation Figure 1: ATA00501 Equivalent Circuit 08/2001 1 ATA00501 Table 1: ATA00501D1C Pad Description (Die Only) PAD VD D 1 VD D 2 IIN V OUT C A GC C BY D E S C R IP TION VD D 1 VD D 2 TIA Input C urrent TIA Output Voltage E xternal A GC C apaci tor C OMME N T P osi ti ve supply for i nput gai n stage P osi ti ve supply for second gai n stage C onnect detector cathode for proper operati on Requi res external D C block 70K * C A GC = A GC ti me constant Input gai n stage bypass capaci tor >56 pF 12 VDD2 VDD1 11 10 GND 925 um 19F IIN GND GND GND GND CBY CBY 1 GND 1992 9 8 7 2 3 VOUT GND CAGC GND 1250 um 4 5 6 Figure 2: Bonding Pad Layout (Die Only) P IN 1 2 3 4 5 6 D E S C R IP TION NC GND IIN C BY GND C AGC P IN 7 8 9 10 11 12 Figure 3: Pin Layout Table 2:ATA00501S2C Pin Description D E S C R IP TION V OUT GND NC VDD GND NC ELECTRICAL CHARACTERISTICS V DD1 V DD2 IIN TA TS Table 3: Absolute Maximum Ratings 7.0 V 7.0 V 5 mA Operati ng Temp. - 40 o C to 125 o C Storage Temp. - 65 o C to 150 o 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. 21. PRELIMINARY DATA SHEET - Rev 1.5 08/2001 ATA00501 Table 4: Electrical Specifications PAR AME TE R 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. 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 41. degradation in bandwidth and sensitivity (see Bandwidth vs. CT curves). Figure 6: Bandwidth vs. Temperature C T = 0.5 pF 0.09 0.08 0.07 0.06 0.05 0.04 -40 10 60 85 VDD = 5.5 V VDD = 5.0 V VDD = 4.5 V Temperature (C) PRELIMINARY DATA SHEET - Rev 1.5 08/2001 ATA00501 Figure 7: Bandwidth vs. CT Figure 9: Bandwidth vs. IIN 1.44 1.24 90 80 Bandwidth (MHz) / B(3dB)≈ A2π Rf (Cin +Ct) VDD = 5.5 V VDD= 5.0 V VDD= 4.5 V VDD = 4.5 V IIN Rf Bandwidth (GHz) 70 60 50 40 30 0 0.2 VDD = 5.5 V 1.04 .84 .64 .44 .24 50 .04 0.4 0.6 0.8 1 1.2 - 2.1 - 1.6 - 1.1 - 0.6 - 0.1 Note: All performance curves are typical @ TA =25 oC unless otherwise noted. CT(pF) IIN (mA DC) 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. Figure 10: VOUT vs. IIN 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 IIN Connection (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 25mA, the specifications for optical overload will not be met. Figure 8: Transimpedance vs. IIN 25 22 19 16 IIN VDD = 5.5 V VDD = 4.5 V 50 Transimpedance (K Ohm) 13 10 7 4 1 -0.1 Output Collapse Heavy AGC VOUT (Volts) VDD = 5.5 V Linear Region Rf IIN vOUT VDD = 4.5 V -4 -3 -2 -1 -2.1 -1.6 -1.1 -0.6 IIN (mA DC) IIN (mA DC) PRELIMINARY DATA SHEET - Rev 1.5 08/2001 5 ATA00501 Figure 11: Input Offset Voltage vs. Temperature 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. 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 30 MHz lowpass filter at the output of the TIA) divided by the AC transresistance. Figure 12: Input Referred Noise Spectral Density 1.9 1.85 1.8 1.75 1.7 1.65 1.6 1.55 1.5 Input Offset Voltage VDD = 5.5 V V = 5.0V DD VDD = 4.5V 10 Temperature oC 60 - 40 CBY Connection 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. 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. 7 Hz 6 5 4 3 2 1 CT Rf 50 pA/ C T=1.0pF CT =0.5pF 1 10 100 1000 - 0.1 Frequency (MHz) FIgure 13: Input Referred Noise vs Temperature Input Referred Noise in (nA RMS) Input Referred Noise Test Circuit 10 25dB VDD = 4.5 V 30 MHz LPF 9 8 7 6 5 -40 0 0.5pF TIA VDD =5.5V η(dBm) = 10 LOG 6500 in R 40 0 80 Temperature ( C) 61. PRELIMINARY DATA SHEET - Rev 1.5 08/2001 ATA00501 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. Figure 14: Phase (IIN to VOUT) 180 200 Rf Degrees 220 240 IIN 0.5pF VOUT 50 100 150 Frequency (MHz) PRELIMINARY DATA SHEET - Rev 1.5 08/2001 7 ATA00501 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° 0o 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: ATA00501S2C Package Pin-Out (S2C) Dimensions in Inches (Millimeters) ORDERING INFORMATION PAR T N U MB ER ATA00501D 1C ATA00501S2C 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 8 PRELIMINARY DATA SHEET - REV 1.5 08/2001