SY88353BL 3.3V, 3.2 Gbps Limiting Post Amplifier with Programmable Decision Threshold General Description Features The SY88353BL limiting post amplifier is designed for use in fiber-optic receivers, and is specially optimized for WDM applications where optical amplifiers such as EDFAs and Raman amplifier are used. The device connects to typical transimpedance amplifiers (TIAs). The linear signal from TIAs can contain significant amounts of noise that is unevenly distributed between top and bottom rails due to the ASE noise generated by the optical amplifiers, crosstalk, or non-linear effect in the fiber. In order to optimize the BER in such noisy conditions, the decision threshold between bit 1 and bit 0, needs to be moved to the rail that contains less noise. The SY88353BL features a pin at which an external voltage can be applied to move the crossing point up and down, from 20% to 80%, for BER optimization purposes. The SY88353BL operates from a single +3.3V power supply, over temperatures ranging from –40oC to +85oC. Signals with data rates from 155Mbps up to 3.2Gbps, and as small as10mVpp, can be amplified to drive devices with CML or PECL inputs. The SY88353L features a Loss-of-Signal (LOS) opencollector TTL output. A programmable Loss-of-Signal level set pin (LOSLVL) sets the sensitivity of the input amplitude detection. LOS asserts high if the input amplitude falls below the threshold sets 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, 3.3dB 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 155Mbps to 3.2Gbps operation Low-noise CML data outputs Chatter-free Open-Collector TTL loss-of-signal (LOS) output TTL /EN input Programmable LOS level set (LOSLVL) Programmable Decision Threshold Available in a tiny 3mm x 3mm MLF® package Applications • • • • WDM Systems Gigabit Ethernet, 1X and 2X Fibre Channel SONET/SDH: OC-3/12/24/48 – STM1/4/8/16 Low-gain TIA interface Markets • Datacom/telecom • Optical transceiver MLF and MicroLeadFrame are registered trademarks of Amkor Technology. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com February 2007 1 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Typical Application Circuit Programmable Decision Threshold Fixed Decision Threshold Ordering Information Package Type Operating Range Package Marking SY88353BLMG MLF-16 Industrial 353B with Pb-Free bar line indicator NiPdAu Pb-Free SY88353BLMGTR(1) MLF16 Industrial 353B with Pb-Free bar line indicator NiPdAu Pb-Free Part Number Lead Finish Note: 1. Tape and Reel. Pin Configuration 16-Pin MLF® (MLF-16) February 2007 2 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Pin Description Pin Number Pin Name Type Pin Function 1 DIN Data Input True data input. 4 /DIN Data Input Complementary data input. 5 VTHN DC Input 6 VTHREF 7 LOS Open-collector TTL output Tie this pin to pin 6 (VTHREF) and apply a DC voltage on pin 16 (VTHP) for signal crossing adjustment. Connect to ground if no crossing adjustment is needed. 1.25V Reference voltage (referenced to ground) for decision threshold adjustment. Loss-of-Signal: asserts high when the data input amplitude falls below the threshold set by LOSLVL. 9 /DOUT CML Output Complementary data output. 12 DOUT CML Output True data output. 14 LOSLVL Input 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. 15 /EN TTL Input: Default is HIGH. /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. 16 VTHP DC Input Apply a DC voltage from 0 to 2.4V to adjust the signal crossing level when pin 5 (VTHN) is tied to pin 6 (VTHREF). 1.25V sets the crossing close to 50%. Connect to ground if no crossing adjustment is needed. 2, 3, 10, 11 GND Ground 8, 13 VCC Power Supply February 2007 Device ground. Positive power supply. 3 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VCC) ....................................... 0V to +4.0V Input Voltage (DIN, /DIN) .......................................0 to VCC Output Current (IOUT) Continuous........................................................ ±25mA /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 Supply Voltage (VCC) ........................... +3.0V to +3.6V Ambient Temperature (TA).................. –40°C to +85°C Package Thermal Resistance(3) MLF® (θJA) Still-air ............................................... 60°C/W (ψJB) ........................................................... 33°C/W DC Electrical Characteristics VCC = 3.0 to 3.6V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C. Symbol Parameter Condition Min Typ ICC Power Supply Current No output load LOSLVL LOSLVL Voltage VOH DOUT, /DOUT HIGH Voltage VCC-0.020 VCC-0.005 VOL DOUT, /DOUT LOW Voltage VCC-0.475 VCC-0.400 VCC-0.350 VOFFSET Differential Output Offset VTHREF Decision Threshold Reference Voltage Z0 Single-Ended Output Impedance 40 50 60 Ω ZI Single-Ended Input Impedance 40 50 60 Ω Min Typ Max Units 20 % 45 VCC -1.3 Max Units 62 mA VCC V VCC V ±80 1.25 V mV V TTL DC Electrical Characteristics VCC = 3.0 to 3.6V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C. Symbol VIH Parameter Condition Output signal Crossing Range Lower Limit VTHN connected to VTHREF and 02.4V applied to VTHP. Output signal Crossing Range Upper Limit 20 ≤ DIN ≤ 100(mVpp), see Figure on page 6. /EN Input HIGH Voltage VIL /EN Input LOW Voltage IIH /EN Input HIGH Current 80 % 2.0 V 0.8 V VIN = 2.7V 20 µA VIN = VCC 100 µA IIL /EN Input LOW Current VIN = 0.5V ICEX LOS Output Leakage Current VOUT = VCC 100 µA VOL LOS Output LOW Level Sinking 2mA 0.5 V February 2007 -0.3 4 mA M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL AC Electrical Characteristics VCC = 3.0 to 3.6V; RLoad = 50Ω to VCC; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C. Symbol Parameter Condition tr, tf Output Rise/Fall Time (20% to 80%) tJITTER Deterministic Random Min Typ Max Note 4 60 100 Note 5 15 psPP Note 6 5 psRMS 20 ps VID Differential Input Voltage Swing VOD Differential Output Voltage Swing TOFF LOS Release Time Note 9 TON LOS Assert Time Note 9 LOSAL Low LOS Assert Level RLOSLVL = 15kΩ, Note 7 9 mVPP LOSDL Low LOS De-assert Level RLOSLVL = 15kΩ, Note 7 13 mVPP HYSL Low LOS Hysteresis RLOSLVL = 15kΩ, Note 8 3.2 dB LOSAM Medium LOS Assert Level RLOSLVL = 5kΩ, Note 7 17 mVPP LOSDM Medium LOS De-assert Level RLOSLVL = 5kΩ, Note 7 25 mVPP HYSM Medium LOS Hysteresis RLOSLVL = 5kΩ, Note 8 3.3 dB LOSAH High LOS Assert Level RLOSLVL = 100Ω, Note 7 47 mVPP LOSDH High LOS De-assert Level RLOSLVL = 100Ω, Note 7 70 mVPP HSYH High LOS Hysteresis RLOSLVL = 100Ω, Note 8 3.4 dB B-3dB 3dB Bandwidth 2.0 GHz AV(Diff) Differential Voltage Gain 38 dB S21 Single-Ended Small-Signal Gain 32 dB Note 4 700 26 1800 Units 800 950 2 10 2 10 mVPP mVPP µs µs 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 ratings 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. 3. Package Thermal Resistance assumes exposed pad is soldered (or equivalent) to the devices most negative potential on the PCB. ψJB uses a 4-layer and θJA in still-air number, unless otherwise stated. 4. Amplifier in limiting mode. Input is a 200MHz square wave. 5. Deterministic jitter measured using 2.5Gbps K28.5 pattern, VID = 10mVPP. 6. Random jitter measured using 2.5Gbps K28.7 pattern, VID = 10mVPP. 7. 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. 8. 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 upon 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. 9. 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-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Typical Operating Characteristics VCC = 3.3V, TA = 25°C, RL = 50Ω to VCC-2V, unless otherwise stated. LOSLVL RESISTOR (Ω) February 2007 6 LOSLVL RESISTOR (Ω) M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Functional Characteristics VCC = 3.3V, TA = 25°C, RL = 50Ω to VCC-2V, unless otherwise stated. February 2007 7 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Functional Block Diagram Detailed Description The SY88353L limiting post amplifier operates from a single +3.3V power supply, over temperatures from –40°C to +85°C. Signals with data rates from 155Mbps up to 3.2Gbps, and as small as 10mVpp, can be amplified. Figure 1 shows the allowed input voltage swing. The SY88353L generates a LOS output that can be feedback to /EN for output stability in the absence of a signal at the input. LOSLVL sets the sensitivity of the input amplitude detection. The amplifier features a signal crossing adjustment for BER optimization in optical links using optical amplifiers such in WDM applications. Input Amplifier/Buffer Figure 2 shows a simplified schematic of the input stage. The input amplifier allows signals as small as 10mVpp to be detected and amplified. The input amplifier allows input signals as large as 1800mVpp. Input signals are linearly amplified with a typical 38dB differential voltage gain. Since it is a limiting amplifier, the SY88353BL outputs typically 800mVpp voltage-limited waveforms for input signals that are greater than 12mVpp. Applications requiring the SY88353L to operate with high gain should have the upstream TIA placed as close as possible to the SY88353BL’s input pins to ensure the best performance of the device. Output Buffer The SY88353BL’s CML output buffer is designed to drive 50Ω lines and is internally terminated with 50Ω to VCC. Figure 3 shows a simplified schematic of the output stage. February 2007 Loss-of-Signal The SY88353L generates a chatter-free loss-of-signal (LOS) open-collector, TTL output, as shown in Figure 4. LOS is used to determine if 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, 3.3dB 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 VCC1.3V. The external resistor creates a voltage divider between VCC and VCC-1.3V, as shown in Figure 5. Hysteresis The SY88353L typically provides 3.3dB LOS electrical hysteresis, which is defined as 20log (VINLOS-De-assert/ VINLOS-Assert). Since the relationship between the voltage out of the ROSA and optical power at its input is linear, the optical hysteresis will be typically half of the electrical hysteresis reported in the datasheet. In practice, the ratio between electrical and optical hysteresis is found to be within the range 1.5 to 1.8dB. Thus, 3.3dB electrical hysteresis will correspond to an optical hysteresis within the range 1.8 to 2.2dB. 8 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Signal Crossing Adjustment In order to optimize the decision threshold level and hence, the BER of the optical link, the SY88353L provides two pins for output signal crossing control. The signal crossing can be adjusted by connecting VTHN (pin 5) to VTHREF (pin 6), and applying a DC signal at VTHP (pin 16). By varying the DC signal at VTHP from – 0V to 2.5V – while the input signal to the post amplifier is less than 100mVpp, the crossing of the output signal will change from 20% to 80% reaching 50% when VTHP = VTHREF = 1.25V. If the crossing control function is not needed, VTHN and VTHP must be connected to ground. The zero crossing vs. VTHP plot, shown on page 6, shows how the crossing of the output signal changes with the voltage applied at VTHP (pin 16) while VTHN (pin 5) is tied to VTHREF (pin 6) for different input signal levels. Figure 1. VIS and VID Definition Figure 2. Input Structure February 2007 Figure 3. Output Structure 9 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL 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 AN-45 Notes on Sensitivity and Hysteresis in Micrel Post Amplifiers http://www.micrel.com/product-info/app_hints+notes.shtml February 2007 10 M9999-021707-B [email protected] or (408) 955-1690 Micrel, Inc. SY88353BL Package Information 16-Pin (3mm x 3mm) MLF® (MLF-16) 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. © 2006 Micrel, Incorporated. February 2007 11 M9999-021707-B [email protected] or (408) 955-1690