1.25Gbps HIGH-SPEED LIMITING POST AMPLIFIER DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ Up to 1.25Gbps operation Low noise Chatter-Free LOS Generation Open Collector TTL LOS Output TTL /EN Input Differential PECL inputs for data Single power supply Designed for use with SY88902 and SY88904 Available in a tiny 10-pin (3mm) MSOP The SY88903 limiting post amplifier with its high gain and wide bandwidth is ideal for use as a post amplifier in fiber-optic receivers with data rates up to 1.25Gbps. Signals as small as 5mVp-p can be amplified to drive devices with PECL inputs. The SY88903 generates a chatter-free Loss of Signal (LOS) open collector TTL output. The SY88903 incorporates a programmble level detect function to identify when the input signal has been lost. This information can be fed back to the /EN input of the device to maintain stability under loss of signal conditions. Using LOSLVL pin the sensitivity of the level detect can be adjusted. The LOS LVL voltage can be set by connecting a resistor divider between VCC and VREF, Figure 3. Figure 4 shows the relationship between input level sensitivity and the voltage set on LOSLVL. Figure 5 shows the relationship between input level sensitivity and resistor divider ratio. The LOS output is a TTL open collector output that requires pull-up resistor for proper operation, Figure 1. PIN CONFIGURATION /EN 1 10 VCC DIN 2 /DIN 3 SY88903 9 DOUT MSOP K10-1 8 /DOUT VREF 4 7 LOS LOSLVL 5 6 GND +5V 2k SY88903 LOS APPLICATIONS ■ ■ ■ ■ 1.25Gbps Gigabit Ethernet 531Mbps and 1062Mbps Fibre Channel 622Mbps SONET Gigabit Interface Converter Figure 1. LOS Output with Desired Rise Time BLOCK DIAGRAM DIN Limiting Amplifier DOUT ECL Buffer DOUT DIN VREF Enable VCC GND EN Level Detect LOS LOSLVL Rev.: G 1 Amendment: /1 Issue Date: July 2000 SY88903 Micrel PIN NAMES Pin GENERAL DESCRIPTION Type DIN Data Input /DIN Data Input Data Input LOS LVL General The SY88903 is an integrated limiting amplifier intended for high-frequency fiber-optic applications. The circuit connects to typical transimpedance amplifiers found within a fiber-optics link. The linear signal output from a transimpedance amplifier can contain significant amounts of noise, and may vary in amplitude over time. The SY88903 limiting amplifier quantizes the signal and outputs a voltagelimited waveform. The TTL /EN pin allows the user to disable the output signal without removing the input signal. Function Inverting Data Input Input Loss of Signal Level Set /EN TTL Input Output Enable (active Low) LOS TTL Output (Open Collector) Loss of Signal Indicator (active High) GND Ground Ground DOUT PECL Output Data Output /DOUT PECL Output Inverting Data Output VCC Power Supply Positive Power Supply VREF Output Reference Voltage Output for LOS Level Set (see Fig. 3) ABSOLUTE MAXIMUM RATINGS(1) Symbol Rating Value Unit VCC Power Supply Voltage 0 to +7.0 V DIN, /DIN Input Voltage 0 to VCC V DOUT, /DOUT Output Voltage (with 50Ω load) VCC –2.5, VCC +0.3 V TA Operating Temperature Range –40 to +85 °C Tstore Storage Temperature Range –55 to +125 °C NOTE: 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 RATlNG conditions for extended periods may affect device reliability. 2 SY88903 Micrel DC ELECTRICAL CHARACTERISTICS VCC = +5V ±10%, RLOAD = 50Ω to VCC-2V, TA = –40°C to +85°C TA = –40°C Symbol Parameter Power Supply IIL /EN Input LOW Current TA = +25°C TA = +85°C Min. Max. Min. Max. Min. Typ. Max. Min. Max. Unit — 35 — 35 — 21 35 — 35 mA –0.3 — –0.3 — –0.3 — — –0.3 — mA 20(5) 100(6) — — 20(5) 100(6) — — 20(5) 100(6) — — 20(5) 100(6) µA Current(1) ICC TA = 0°C IIH /EN Input HIGH Current — — VCMR Common Mode Range GND +2.0 Voffset Differential Output Offset LOSLVL LOSLVL Level VOL — — VCC -1.0 GND +2.0 VCC -1.0 GND +2.0 — VCC -1.0 GND +2.0 VCC -1.0 V — ±100 — ±100 — — ±100 — ±100 mV VREF VCC VREF VCC VREF — VCC VREF VCC V LOS Output Low Level(2) — 0.5 — 0.5 — — 0.5 — 0.5 V IOH LOS Output Leakage(3) — 250 — 250 — — 250 — 250 uA VOH DOUT and /DOUT HIGH Output VCC-1085 VCC-880 VCC-1025 VCC-880 VCC-1025 VCC-955 VCC-880 VCC-1025 VCC-880 mV VOL DOUT and /DOUT LOW Output VCC-1830 VCC-1810 VCC–1620 mV VREF Reference Supply(4) VCC-2.625 VCC–2.325 VCC-2.625 VCC–2.325 VCC-2.625 VCC–2.475 VCC–2.325 VCC-2.625 VCC–2.325 VIH /EN Input HIGH Voltage 2.0 — 2.0 — 2.0 — — 2.0 — V VIL /EN Input LOW Voltage — 0.8 — 0.8 — — 0.8 — 0.8 V VCC–1555 VCC-1810 VCC–1620 VCC-1810 VCC–1705 VCC–1620 NOTES: 1. No output load 2. IOL = + 2mA 3. VOH = 5.5V V 4. IREF must be limited to be within -0.8mA (source) and 0.5mA (sink). 5. VIN = 2.7V 6. VIN = VCC AC ELECTRICAL CHARACTERISTICS VCC = +5V ±10%, RLOAD = 50Ω to VCC - 2V, TA = –40°C to +85°C TA = –40°C Symbol Parameter PSRR Supply(1) TA = 0°C TA = +25°C TA = +85°C Min. Max. Min. Max. Min. Typ. Max. Min. Max. Unit Conditions Power Rejection Ratio — — — — — 35 — — — dB VID Input Voltage Range 5 1800 5 1800 5 — 1800 5 1800 mVp-p tr, tf Output Rise/Fall Time — — 350 — — — 350 — — — 200 trin,tfin 350 — — — 350 — ps VID > 100mVp-p VID < 100mVp-p VOD Differential Output Voltage Swing(2) — — — — — — — — — — 600 200 — — — — — — mV mV VID = 15mVp-p VID = 5mVp-p tOFFL LOS Release Time(3) Minimum Input — 0.5 — 0.5 — 0.1 0.5 — 0.5 µs tOFFH LOS Release Time(4) Maximum Input — 0.5 — 0.5 — 0.1 0.5 — 0.5 µs tONL LOS Assert Time(3) — 0.5 — 0.5 — 0.2 0.5 — 0.5 µs VSR LOS Sensitivity Range 5 50 5 50 5 — 50 5 50 mVp-p HYS LOS Hysteresis 2 8 2 8 2 4.6 8 2 8 dB Input referred, 55MHz 3. Input is a 200MHz square wave, tr < 300ps, 8mVp-p. 4. Input is a 200MHz square wave, tr < 300ps, 1.8Vp-p. NOTES: 1. Input referred noise = RMS output noise/low frequency gain. 2. Input is 622MHz square wave. 3 SY88903 Micrel APPLICATION INFORMATION Output Termination The SY88903 outputs must be terminated with a 50Ω load to VCC – 2V (or Thevenin equivalent). The SY88903 ground pin should be connected to the circuit board ground. Use multiple PCB vias close to the part to connect to ground. Avoid long, inductive runs which can degrade performance. Layout and PCB Design Since the SY88903 is a high-frequency component, performance can largely be determined by board layout and design. A common problem with high-gain amplifiers is feedback from the large swing outputs to the input via the power supply. NOTES: Resistor Divider = R2/ (R1 + R2) R1 + R2 ≥ 5kΩ VCC R1 0.1µF DIN– LOSLVL R2 50Ω DIN+ 50Ω 0.1µF VREF VREF 0.1µF Figure 3. LOSLVL Circut Figure 2. Differential Input Configuration PRODUCT ORDERING CODE 4 Ordering Code Package Type Operating Range SY88903KC K16-1 Commercial SY88903 Micrel PERFORMANCE CURVE 100.00 90.00 Deassert 80.00 70.00 AA AA AA A A AA A AA AA A A A AA AAAAAA AA AA A A AAAAA AA AA AAA AA AAAA A AA AA AA Level (mV) 60.00 Assert 50.00 40.00 30.00 20.00 10.00 5.00 4.75 4.88 4.63 4.38 4.51 4.13 4.26 4.01 3.76 3.89 3.52 3.64 3.39 3.14 3.27 2.90 3.02 2.77 2.53 2.65 0.00 LOSlvl (V) Figure 4. LOS Assert and Deassert Levels vs LOSLVL 100.00 90.00 80.00 Deassert 70.00 Assert 50.00 40.00 30.00 20.00 10.00 1.00 0.95 0.90 0.85 0.75 0.80 0.70 0.65 0.60 0.50 0.55 0.45 0.40 0.35 0.25 0.30 0.20 0.15 0.10 0.00 0.00 0.05 Level (mV) 60.00 Resistor Divider R2 / (R1 + R2) Figure 5. LOS Assert and Deassert Levels vs Resistor Divider 5 SY88903 Micrel APPLICATION EXAMPLE FOR 3-CHIP SET SOLUTION GBIC Terminal TX_DATA+ VCC DIN DIN LOSOUT EN VREF RSET 20kΩ VREF GND SY88902 VCC IBIAS SY88905 GND VCC OUT RSER VCC 20kΩ 20kΩ OUT MD IBIAS SET IBIAS FB IPIN SET DIN DIN 0.1µF BLM21A102S VCC Laser Module The value of RSER depends on the Laser Diode. VCC 6 24Ω LOSLVL 82Ω LOSIN VCC LOS SY88903 VREF 130Ω Laserdiode REXT 1000pF 82Ω 82Ω 82Ω Photodiode 130Ω 130Ω 130Ω TX_DATA– VCC EN DOUT DOUT GND 0.1µF 82Ω 82Ω ENABLE/DISABLE RX_LOS RX_DATA+ RX_DATA– VCC 20kΩ 130Ω 130Ω SY88903 Micrel 10 LEAD MSOP (K10-1) Rev. 00 7 SY88903 Micrel MICREL-SYNERGY TEL 3250 SCOTT BOULEVARD SANTA CLARA CA 95054 USA + 1 (408) 980-9191 FAX + 1 (408) 914-7878 WEB http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. © 2000 Micrel Incorporated 8