SY88903AL 3.3V, Burst Mode 1.25Gbps PECL HighSensitivity Limiting Post Amplifier with TTL Loss-of-Signal General Description Features The SY88903AL, burst mode, high-sensitivity limiting post amplifier is designed for use in fiber-optic receivers, specially optimized for passive optical networks (PONs). The device connects to typical transimpedance amplifiers (TIAs). The linear signal output from TIAs can contain significant amounts of noise and may vary in amplitude over time. The SY88903AL quantizes these signals and outputs PECL level waveforms. The SY88903AL operates from a single +3.3V power supply, over temperatures ranging from –40oC to +85oC. Signals with data rates from 622Mbps up to 1.25Gbps, and as small as 5mVpp, can be amplified to drive devices with PECL inputs. The SY88903AL generates a Loss-of-Signal (LOS) open-collector TTL output. A programmable Loss-ofSignal level set pin (LOSLVL) sets the sensitivity of the input amplitude detection. LOS asserts high if the input amplitude falls below the threshold set by LOSLVL and de-asserts low otherwise. The enable bar input (/EN) de-asserts the true output signal without removing the input signal. The LOS output can be fed back to the /EN input to maintain output stability under a loss-of-signal condition. Typically, 3.4dB LOS hysteresis is provided to prevent chattering. All support documentation can be found on Micrel’s web site at: www.micrel.com. • Single 3.3V power supply • Fast LOS release/assert (<500ns) time for PON applications • 622Mbps to 1.25Gbps operation • Low-noise PECL data outputs • High gain LOS • Chatter-free Open-Collector TTL signal detect (LOS) output with internal 4.75kΩ pull-up resistor • TTL /EN input • Programmable LOS level set (LOSLVL) • Available in a tiny 10-pin MSOP package February 2007 1 Applications • • • • • GPON/GEPON/EPON Gigabit Ethernet, 1062Mbps Fibre Channel OC-12/24 SONET/SDH Low-gain TIA interface High-gain line driver and line receiver Markets • FTTH/FTTP • Datacom/telecom • Optical transceiver M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Typical Application Circuit February 2007 2 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Ordering Information Lead Finish Package Type Operating Range Package Marking SY88903ALKG K10-1 Industrial 903A with Pb-Free bar line indicator NiPdAu Pb-Free SY88903ALKGTR(1) K10-1 Industrial 903A with Pb-Free bar line indicator NiPdAu Pb-Free Part Number Note: 1. Tape and Reel. Pin Configuration 10-Pin MSOP (K10-1) Pin Description Pin Number Pin Name Type 1 /EN TTL Input: Default is HIGH. 2 DIN Data Input True data input. 3 /DIN Data Input Complementary data input. 4 VREF 5 LOSLVL Input 6 GND Ground 7 LOS Open-collector TTL output w/internal 4.75kΩ pull-up resistor 8 /DOUT PECL Output Complementary data output. 9 DOUT PECL Output True data output. 10 VCC Power Supply Positive power supply. February 2007 Pin Function /Enable: This input enables the outputs when it is LOW. Note that this input is internally connected to a 25kΩ pull-up resistor and will default to a logic HIGH state if left open. Reference voltage: Placing a capacitor here to VCC helps stabilize LOSLVL. Loss-of-Signal Level Set: a resistor from this pin to VCC sets the threshold for the data input amplitude at which LOS will be asserted. Device ground. Loss-of-Signal: asserts high when the data input amplitude falls below the threshold set by LOSLVL. 3 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VCC) ....................................... 0V to +7.0V Input Voltage (DIN, /DIN) .......................................0 to VCC Output Current (IOUT) Continuous........................................................ ±50mA Surge .............................................................. ±100mA /EN Voltage ............................................................0 to VCC VREF Current .......................................... -800µA to +500µA LOSLVL Voltage................................................. VREF to VCC Lead Temperature (soldering, 20sec.) ..................... 260°C Storage Temperature (Ts) ....................... –65°C to +150°C Supply Voltage (VCC)............................. +3.0V to +3.6V Ambient Temperature (TA) ................... –40°C to +85°C Junction Temperature (TJ) ................. –40°C to +120°C Junction Thermal Resistance MSOP (θJA) Still-air ................................... 113°C/W DC Electrical Characteristics VCC = 3.0 to 3.6V; RL = 50Ω to VCC-2V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C. Symbol Parameter Condition Min Typ Max Units ICC Power Supply Current No output load 26 39 mA LOSLVL LOSLVL Voltage VCC V VOH PECL Output HIGH Voltage VCC-1.085 VCC-0.955 VCC-0.880 V VOL PECL Output LOW Voltage VCC-1.850 VCC-1.705 VCC-1.555 V VIHCMR Common Mode Range GND+2.0 V VREF Reference Voltage VCC-1.48 VCC-1.32 VCC-1.16 VREF VCC V TTL DC Electrical Characteristics VCC = 3.0 to 3.6V; RL = 50Ω to VCC-2V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C. Symbol Parameter VIH /EN Input HIGH Voltage VIL /EN Input LOW Voltage IIH /EN Input HIGH Current IIL /EN Input LOW Current VOH LOS Output HIGH Level VOL LOS Output LOW Level Condition Min Typ Max 2.0 Units V 0.8 V VIN = 2.7V 20 µA VIN = VCC 100 µA VIN = 0.5V -0.3 VCC > 3.3V, IOH-MAX < 160µA 2.4 V VCC < 3.3V, IOH-MAX < 160µA 2.0 V IOL = +2mA mA 0.5 V Notes: 1. Permanent device damage may occur if absolute maximum ratings are exceeded. This is a stress rating only and functional operation is not implied at conditions other than those detailed in the operational sections of this data sheet. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2. The data sheet limits are not guaranteed if the device is operated beyond the operating ratings. February 2007 4 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL AC Electrical Characteristics VCC = 3.0 to 3.6V; RL = 50Ω to VCC-2V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C. Symbol Parameter tr, tf Output Rise/Fall Time (20% to 80%) tJITTER Condition Min Typ Note 3 Max 260 Units ps Deterministic Note 4 15 psPP Random Note 5 5 psRMS VID Differential Input Voltage Swing See Figure 1 VOD Differential Output Voltage Swing VID > 18mVPP, See Figure 1 tOFF LOS Release Time Note 8 40 500 ns tON LOS Assert Time 125 500 ns 5 1800 mVPP mVPP 1500 LOSAL Low LOS Assert Level Note 8 RLOSLVL = 15kΩ, Note 6 2.3 mVPP LOSDL Low LOS De-assert Level RLOSLVL = 15kΩ, Note 6 3.4 mVPP HSYL Low LOS Hysteresis RLOSLVL = 15kΩ, Note 7 3.4 dB LOSAM Medium LOS Assert Level RLOSLVL = 5kΩ, Note 6 LOSDM Medium LOS De-assert Level RLOSLVL = 5kΩ, Note 6 HSYM Medium LOS Hysteresis RLOSLVL = 5kΩ, Note 7 LOSAH High LOS Assert Level RLOSLVL = 100Ω, Note 6 LOSDH High LOS De-assert Level RLOSLVL = 100Ω, Note 6 HSYH High LOS Hysteresis RLOSLVL = 100Ω, Note 7 B-3dB 3dB Bandwidth AV(Diff) Differential Voltage Gain S21 Single-Ended Small-Signal Gain 2 4.2 mVPP 6.2 9 mVPP 2 3.4 5 dB 8 10.8 2 30 mVPP 16.4 21 mVPP 3.4 5 dB 1 GHz 42 dB 36 dB Notes: 3. Amplifier in limiting mode. Input is a 200MHz square wave. 4. Deterministic jitter measured using 1.25Gbps K28.5 pattern, VID = 10mVPP. 5. Random jitter measured using 1.25Gbps K28.7 pattern, VID = 10mVPP. 6. See “Typical Operating Characteristics” for a graph showing how to choose a particular RLOSLVL for a particular LOS assert and its associated de-assert amplitude. 7. This specification defines electrical hysteresis as 20log (LOS De-assert/LOS Assert). The ratio between optical hysteresis and electrical hysteresis is found to vary between 1.5 and 2 depending upon the level of received optical power and ROSA characteristics. Based on that ratio, the optical hysteresis corresponding to the electrical hysteresis range 1dB-4.5 dB, shown in the AC characteristics table, will be 0.5dB-3dB Optical Hysteresis. 8. In real world applications, the LOS Release/Assert time can be strongly influenced by the RC time constant of the AC-coupling cap and the 50Ω input termination. To keep this time low, use a decoupling cap with the lowest value that is allowed by the data rate and the number of consecutive identical bits in the application (typical values are in the range of 0.001µF to 1.0µF). February 2007 5 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Typical Operating Characteristics VCC = 3.3V, TA = 25°C, RL = 50Ω to VCC-2V, unless otherwise stated. February 2007 6 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Functional Block Diagram Detailed Description The SY88903AL high-sensitivity limiting post amplifier operates from a single +3.3V power supply, over temperatures from –40°C to +85°C. Signals with data rates from 622Mbps up to 1.25Gbps, and as small as 5mVpp, can be amplified. Figure 1 shows the allowed input voltage swing. The SY88903AL generates an LOS output, allowing feedback to /EN for output stability. LOSLVL sets the sensitivity of the input amplitude detection. Input Amplifier/Buffer Figure 2 shows a simplified schematic of the input stage. The high-sensitivity of the input amplifier allows signals as small as 5mVpp to be detected and amplified. The input amplifier allows input signals as large as 1800mVpp. Input signals are linearly amplified with a typically 42dB differential voltage gain. Since it is a limiting amplifier, the SY88903AL outputs typically 1500mVpp voltage-limited waveforms for input signals that are greater than 12mVpp. Applications requiring the SY88903AL to operate with high-gain should have the upstream TIA placed as close as possible to the SY88903AL’s input pins to ensure the best performance of the device. Output Buffer The SY88903AL’s PECL output buffer is designed to drive 50Ω lines. The output buffer requires appropriate termination for proper operation. An external 50Ω resistor to VCC–2V for each output pin provides this. Figure 3 shows a simplified schematic of the output stage. February 2007 Loss-of-Signal The SY88903AL generates a chatter-free loss-of-signal (LOS) open-collector TTL output with internal 4.75kΩ pull-up resistor as shown in Figure 4. LOS is used to determine that the input amplitude is too small to be considered a valid input. LOS asserts high if the input amplitude falls below the threshold set by LOSLVL and de-asserts low otherwise. LOS can be fed back to the enable (/EN) input to maintain output stability under a loss of signal condition. /EN de-asserts low the true output signal without removing the input signals. Typically, 3.4dB LOS hysteresis is provided to prevent chattering. Loss-of-Signal-Level Set A programmable LOS level set pin (LOSLVL) sets the threshold of the input amplitude detection. Connecting an external resistor between VCC and LOSLVL sets the voltage at LOSLVL. This voltage ranges from VCC to VREF. The external resistor creates a voltage divider between VCC and VREF, as shown in Figure 5. Hysteresis The SY88903AL provides typically 3.4dB LOS electrical hysteresis. By definition, a power ratio measured in dB is 10log (power ratio). Power is calculated as V2IN/R for an electrical signal. Hence, the same ratio can be stated as 20log (voltage ratio). While in linear mode, the electrical voltage input changes linearly with the optical power and hence, the ratios change linearly. Therefore, the optical hysteresis in dB is half the electrical hysteresis in dB given in the data sheet. The SY88903AL is an electrical device, this data sheet refers to hysteresis in electrical terms. With 3.4dB LOS hysteresis, a voltage factor of 1.5 is required to assert or de-assert LOS. 7 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Figure 1. VIS and VID Definition Figure 2. Input Structure Figure 3. Output Structure Figure 4. LOS Output Structure Figure 5. LOSLVL Setting Circuit Note: Recommended value for RLOSLVL is 15kΩ or less. Related Product and Support Documentation Part Number Function Data Sheet Link Application Notes Notes on Sensitivity and Hysteresis in Micrel Post Amplifiers http://www.micrel.com/product-info/app_hints+notes.shtml February 2007 8 M9999-021707-D [email protected] or (408) 955-1690 Micrel, Inc. SY88903AL Package Information 10-Pin MSOP (K10-1) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2005 Micrel, Incorporated. February 2007 9 M9999-021707-D [email protected] or (408) 955-1690