Preliminary Data Sheet AC89 2.5 Gb/s Transimpedance Amplifier, 5.0 Volt supply Features Single +5 V power supply operation Input noise current = 270 nA rms in 2 GHz bandwidth with a 0.5 pF detector Transimpedance gain = 4.0 k (differential) On-chip automatic gain control gives input current overload of 2.6 mA pk and max output voltage swing of 300 mV pk-pk differential 50 single-ended or 100 differential wire bond selectable outputs On-chip power supply rejection achieves 40 dB rejection up to1 MHz Bandwidth (-3 dB): DC to 2.2 GHz Constant photodiode reverse bias = 3 V, (anode to input, cathode to VCC) Photodiode may be anode or cathode connected -40C to + 100C junction temperature operation Available as bare die Preliminary Information Manufactured using a high yield, silicon bipolar process dynamic range. When using differential outputs, a supply decoupling capacitor is the only external circuitry required. Applications Noise performance is optimized for 2.5 Gb/s operation, with a sensitivity of -27 dBm for 10-10 bit error rate, using a detector with 0.5 pF capacitance and a responsivity of 0.85 A/W. SONET OC-48 Fibre optic data modules The Nortel Networks AC89 is a monolithic, silicon bipolar transimpedance amplifier, providing wideband, low noise preamplification of signal current from a photodetector. It features differential outputs with a single-ended bond option and optimized noise performance, and incorporates an Automatic Gain Control (AGC) mechanism to increase System block diagram Nortel Networks offers a portfolio of optical networking ICs for use in highperformance optical receiver and transmitter applications. The AC89 provides for power and chip-count savings to the designer of fiber-based Datacom or Telecom solutions. Preliminary Information Functional description Amplifier front-end The transimpedance front-end amplifies an input current from a photodetector, at pin TZ_IN, to produce an output with the feedback resistor Rf determining the level of amplification (see "Functional block diagram" below). An automatic gain control loop varies this resistor, to ensure that the output from the front-end does not saturate the output driver stage that follows. This gain control allows input signals of up to 2.6 mA peak. The input transistor and feedback are optimized for noise performance at 2.5 Gb/s. The input pin TZ_IN is biased at 3 V below the supply voltage VCC, allowing a photodetector to have a constant reverse bias by connecting the cathode to VCC. This enables full single rail operation. Alternatively the photodetector may be connected between TZ_IN and GND which provides 2 V nominal reverse bias. The front-end stage has its own supply ground connection (VEE2) to achieve optimum noise performance and maintain integrity of the high-speed signal path. The front-end shares the VCC (+5 V) connection with the remainder of the circuitry, which has a separate ground (VEE1). Output driver stage The output driver acts as a buffer stage, capable of swinging up to 300 mVpk-pk differential into a 100 load. The small output swings allow ease of use with low voltage post amplifiers (e.g. 3.3 V parts). Automatic Gain Control (AGC) The AGC circuit monitors the voltages from the output driver and compares them to an internal reference level produced via the on-chip bandgap reference circuit. When this level is exceeded, the gain of the front-end is reduced by controlling the feedback resistor Rf. A long time-constant integrator is used within the control loop of the AGC with a low frequency cut-off of 5 kHz. Functional block diagram Page 2 of 6 AC89 - 2.5 Gb/s Transimpedance Amplifier, 5.0 Volt supply Preliminary Information Absolute maximum ratings These are stress ratings only. Exposure to stresses beyond these maximum ratings may cause permanent damage to, or affect the reliability of the device. Avoid operating the device outside the recommended operating conditions defined below. Symbol Parameter Minimum Maximum Units VCC Supply voltage -0.7 6.0 V Tstg Storage Temperature -65 150 C Tj Junction temperature -40 120 C Recommended operating conditions Symbol Parameter Minimum Typical Maximum Units VCC Supply voltage 4.7 5.0 5.3 V Tj Operating junction temperature -40 100 C DC electrical characteristics Symbol Parameter ICC Supply Current Vin Input Bias Voltage Vout Typical Maximum Units 65 95 mA VCC -3.5 VCC -3.0 VCC -2.5 V Output Bias Voltage 2.8 3.1 3.4 V Tr Transresistance 6.0 8.0 10.0 k Rout Output resistance AC89 - 2.5 Gb/s Transimpedance Amplifier, 5.0 Volt supply Minimum 50 Page 3 of 6 Preliminary Information AC characteristics Symbol Parameter Minimum Typical Maximum Units BW (3dB) Small Signal Bandwidth at -3dB point 1.7 2.2 3.3 GHz Flfc Low frequency cut-off 5 kHz DRi Input data rate 50 2500 Mb/s Iagc AGC Threshold 36 Tz Differential transimpedance (f = 100 mHz) 3.0 4.0 Iol Input current before overload (2.5 Gb/s NRZ data) 2600 3000 A peak Pol Optical overload +1.8 +2.5 dBm Nrms Input noise current (in 2 Ghz) Sens Optical Sensitivity PSR Power supply rejection (up to 1 MHz) (10-10 B.E.R.) 30 A peak 5.0 k 270 365 nA rms -27 -25.6 dBm 40 dB The above parameters are specified differentially under the following conditions: Applications information * Supply Voltage (VCC) = 4.7 V to 5.3 V * Junction Temperature (Tj) = -40C to 100C For maximum performance it is recommended that the device be used in differential mode with the circuit shown in the "Connections for differential operation" diagram. * Load Resistor (RL) = 2 x 50 AC-coupled via 100 nF capacitors * Photodetector Capacitance (Cd) = 0.5 pF * Photodetector Responsivity = 0.85 A/W * Transimpedance (Tz) measured with <36 A peak photocurrent Connections for differential operation Page 4 of 6 AC89 - 2.5 Gb/s Transimpedance Amplifier, 5.0 Volt supply Preliminary Information In situations where it is necessary to use the device in a singleended mode, this can be achieved using the circuit shown in the "Connections for single-ended operation" diagram. Connections for single-ended operation Bond pad assignment Pad No. Pad Name Type Description Function 1, 8, 11 VCC P Supply Positive Supply (+5 V) 2 BIAS-MON I Test Test Pad (leave unconnected) 3 TZ_IN I Analog Input Pad (connect to photodetector) 4 VEE2 P Supply Negative Supply (0V) - Note this is a separate ground for the input stage, which is AC coupled on chip. There is no DC current through this pad. 5, 7 VEE1 P Supply Negative Supply (0V) 6 -ACGND P Supply Single-ended bond option. Connect to GND (0V) through minimum 1 nF for single-ended output on S_OUTP. Leave open-circuit for differential outputs. See "Connections for singleended operation" diagram on page 5. 9 S_OUTN O Analog Negative differential voltage output. Leave open-circuit for single-ended operation. 10 S_OUTP O Analog Positive differential voltage output. Also positive single-ended output if -ACGND is connected to GND (0V) via 1 nF capacitor. AC89 - 2.5 Gb/s Transimpedance Amplifier, 5.0 Volt supply Page 5 of 6 Preliminary Information Pad layout diagram Note: This diagram is not to scale. Bondpad openings are 82 m x 82 m. There are three VCC pads for ease of wire bonding - these pads are connected on-chip and only one pad is required to be bonded out. For additional information on Nortel Networks products and services offered, please contact your local representative. Copyright 2000 Nortel Networks Corporation. All rights reserved. Nortel Networks High Performance Optical Component Solutions attn: Marketing Department 2745 Iris Street 6th Floor Ottawa, Ontario Canada K2C 3V5 Nortel, Nortel Networks, the Nortel Networks corporate logo, and the globemark design are trademarks of Nortel Networks Corporation. Any thirdparty trademarks are the property of their respective owners. Tel: 1-800-4 NORTEL Fax: 1-613-763-8416 Email: opticalcomponents@nortelnetworks.com The information contained in this document is considered to be accurate as of the date of publication. No liability is assumed by Nortel Networks for use of any information contained in this document, or for infringement of any patent rights or any other proprietary rights of third parties which may result from such use. No license is granted by implication or otherwise under any patent right or any other proprietary right of Nortel Networks. www.nortelnetworks.com/hpocs Publication # 84018.37/03-01 Issue 3 Preliminary information documents contain information on products in their formative or design phase of development. Features, characteristic data and other specifications are subject to change without notice. Contact Nortel Networks for current information on this product. Issued: 7 March 2001 Page 6 of 6