SY88212L 3.3V, 2.5Gbps Laser Diode Driver with Integrated Bias and APC General Description Features The SY88212L is a single supply 3.3V laser driver for datacom and telecom applications with data rates from 155Mbps up to 2.5Gbps. The driver can deliver modulation current up to 85mA, and provides a high compliance voltage that makes it suitable for high-current operation with the laser DC-coupled to it. The drivers have integrated bias and Automatic Power Control (APC) functions. All support documentation can be found on Micrel’s web site at: www.micrel.com. • • • • • • 2.4V minimum laser compliance voltage Operation up to 2.5Gbps Modulation current up to 85mA Bias current up to 70mA Power monitoring Available in 24-pin (4mm x 4mm) QFN package Applications • Multi-rate LAN, MAN applications up to 2.5Gbps: FC, GbE, SONET OC3/12/24 and SDH STM1/4/8 • SFF, SFP modules Markets • Telecom, Datacom ___________________________________________________________________________________________________________ Typical Application Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com April 2008 M9999-040908-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Ordering Information(1) Part Number Package Type Operating Range Package Marking Lead Finish SY88212LMG QFN-24 Industrial 212L with Pb-Free bar-line indicator NiPdAu Pb-Free QFN-24 Industrial 212L with Pb-Free bar-line indicator NiPdAu Pb-Free (2) SY88212MGTR Notes: 1. Contact factory for die availability. Dice are guaranteed at TA = +25°C, DC Electrical only. 2. Tape and Reel. Pin Configuration 24-Pin QFN April 2008 2 M9999-040908-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Pin Description Pin Number Pin Name Pin Function 2 DIN+ Non-inverting input data. Internally terminated with 50Ω to a reference voltage. 3 DIN- Inverting input data. Internally terminated with 50Ω to a reference voltage. 5 /TXDISABLE Transmitter Complementary TXDISABLE. TTL Input. The transmitter is enabled when this pin is asserted High and disabled when this pin is asserted Low. A 6.3kΩ resistor must be installed between pins 6 and GND if /TXDISABLE is used as TTL input 6 TXDISABLE Transmitter Disable. TTL input. The transmitter is enabled when this pin is asserted Low and disabled when this pin is asserted High or left open. A 6.3kΩ resistor must be installed between pin 5 and GND if TXDISABLE is used as TTL input. 7 /EN Active low TTL/CMOS. Internally pulled-up. Pull-down with a 22kΩ or lower resistance or apply a low level signal (<0.8 V) to enable bias and modulation. Keep floating or apply a high level (>2 V) to disable. 9 OSC Internal oscillator setting option. Install a 0 Ω resistor from this pin to VCC or leave it open to set the frequency. Refer to the frequency table. 10 TXFAULT Transmitter Fault Indicator. Open collector. Active High. 12 PWRMON Power Monitor. Provides a current which is proportional to the sum of bias current and half of modulation current. Install a resistor between this pin and GND to convert that current to a voltage. 13 BIAS- Inverting laser bias current output. Pull-up to VCC with a resistor. 14 BIAS+ Non-inverting laser bias current output, sources current when TXDISABLE is inserted Low (see pin 6 description) or /TXDISABLE is inserted High (see pin 5 description). Connect to the cathode of the laser through a resistor. 16 MOD+ Non-inverted modulation current output. Provides modulation current when input data is positive. 17 MOD- Inverted modulation current output. Provides modulation current when input data is negative. 20 MD Input from the laser monitoring photodiode. Connect to the anode of the photodiode for APC operation. 22 BIASMAX Install a resistor between this pin and GND to set the maximum bias current for the closed loop operation. The APC loop controls the bias current up to the level of BIASMAX. When the bias current reaches the maximum value set through this pin, the driver continues to sink a current equal to this maximum. For open loop operations, this pin sets the bias current. 23 MODSET Modulation current setting and control. The modulation current is set by installing an external resistor from this pin to ground or using a current source. 24 APCSET Bias current setting and control. The bias current is set by installing an external resistor from this pin to ground or using a current source. Connect a 50K resistor to GND for open loop operation. 8, 11,19 GND Ground. Ground and exposed pad must be connected to the plane of the most negative potential. 1, 4, 15, 18, 21 VCC Supply Voltage. Bypass with a 0.1µF//0.01µF low ESR capacitor as close to VCC pin as possible. Truth Table Oscillator Frequency DIN+ DIN- /EN L H L H L X X MOD+ (1) MOD- Laser (2) Output H L L L L H H H H L L OSC Frequency (MHz) Open 25 VCC 50 Notes: 1. IMOD = 0 when MOD+ = H. 2. Assuming that the cathode of the laser is tied to MOD+. April 2008 3 M9999-040908-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VCC) .................................... –0.5V to +4.0V CML Input Voltage (VIN) ....................VCC–1.2V to VCC+0.5V TTL Control Input Voltage (VI)..................... 0V to VCC +0.3V 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 (3) Package Thermal Resistance QFN (θJA) Still-air ........................................................ 50°C/W (ψJB) ................................................................... 30°C/W DC Electrical Characteristics TA = –40°C to +85°C and VCC = +3.0V to +3.6V. Unless otherwise noted, typical values are VCC = +3.3V, TA = 25°C, IMOD = 25mA, IBIAS = 20mA. Symbol Parameter Condition Min Modulation and Bias currents excluded Typ 55 Max Units ICC Power Supply Current VMOD_MIN Minimum Voltage Required at the Driver Output, MOD+ and MOD-, for Proper Operation 0.6 V VBIAS_MIN Minimum Voltage Required at the Driver Output, BIAS+ and BIAS-, for Proper Operation 0.8 V IBIAS Bias-ON Current Voltage at Bias pin ≥ 0.8V IBIAS_OFF Bias-OFF Current Current at BIAS pin when /EN is high or TXDISABLE is High RIN Input Resistance at DIN+ and DIN- Single ended 1 42.5 100 50 95 (4) mA 70 mA 150 µA 57.5 Ω VDIFF-IN (DIN) Differential Input Voltage Swing 2400 mVPP VOL APCFAULT Output Low IOL = 2mA 0.5 V IOH APCFAULT Output Leakage VOH = VCC 100 µA VIH High Voltage /EN, TXDISABLE, /TXDISABLE VIL Low Voltage /EN, TXDISABLE, /TXDISABLE VPWRMON Maximum voltage at PWRMON pin IMD Current range at MD pin 2 V 0.8 V 1500 µA 1.25 50 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 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 unless otherwise stated. 4. ICC = 95mA for worst-case conditions with IMOD = 85mA, IBias = 70mA, TA = +85°C, VCC = 3.6V. April 2008 4 M9999-040908-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L AC Electrical Characteristics TA = –40°C to +85°C and VCC = +3.0V to +3.6V. Unless otherwise noted, typical values are VCC = +3.3V, TA = 25°C, IMOD = 25mA, IBIAS = 20mA. Symbol IMOD IMOD_OFF Parameter Condition Data Rate NRZ (5) Modulation Current Modulation OFF Current Min Typ 0.155 2.5 Gbps 10 85 mA DC-coupled, voltage at MOD pin ≥0.6V 10 (6) mA Current at MOD+ when /EN is high or TXDISABLE is Low 150 µA Current at MOD- when /EN is high or TXDISABLE is High 150 µA 85 ps 85 ps 70 Output Current Rise Time 20% to 80%, IMOD = 60mA 60 tf Output Current Fall Time 20% to 80%, IMOD = 60mA 60 tINIT (7) Total Jitter APC Loop Initialization Time Units AC-coupled tr Jitter Max 155Mbps data rate 30 622Mbps data rate 30 1.25Gbps data rate 30 2.5Gbps data rate 30 Power up with /EN Low 12 µs /EN changes from high to low with power ON. 10 µs psPP Notes: 5. Load = 15Ω. 6. Assuming VCC = 3.0V, Laser bandgap voltage = 1V, laser package inductance = 1nH, laser equivalent series resistor = 5 Ω, and damping resistor = 10Ω. 7. Total jitter is measured using 27 – 1 PRBS pattern. March 2008 5 M9999-030708-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Functional Diagram March 2008 6 M9999-030708-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L APC Loop Function At start up, with the driver enabled, the laser turns ON within a few microseconds and its back facet monitoring photodiode starts to generate a photocurrent proportional to the optical power. The photocurrent is fed back to the MD pin on the driver where it’s converted to a voltage. The conversion voltage is compared to APCSET on the driver. At equilibrium, the feedback voltage equals the APCSET voltage and the laser optical power reaches its nominal value. If the laser power deviates from its nominal value, the APC loop brings it back to its nominal setting. Detailed Functional Description The SY88212L laser driver is comprised from a fast modulator, a fast bias circuit, and a digital APC loop that allows for fast laser turn-ON time. The driver features a power monitoring function. BIAS and Modulation Setting Bias and modulation currents are set by installing resistors from APCSET (pin 24) to ground and from MODSET (pin 23) to ground respectively or by applying a negative current at those pins. IMD variation versus RAPCSET resistor, IBIAS variation versus RBIASMAX resistor, and IMOD variation versus RMODSET resistor are shown on page 8. APC Loop Failure TXFAULT is asserted High if the bias current reaches BIASMAX or if the APC loop counter reaches its minimum or its maximum counts. BIASMAX A resistor between BIASMAX pin and ground sets the maximum bias the driver can sink. At normal operation, the bias current tracks the laser optical power through the laser monitoring photodiode and the APC loop to compensate for any power deviation from the nominal value set at the start of operation using APCSET. If for any failure (laser or photodiode degradation, open feedback circuit etc…) the APC loop keeps increasing the bias current trying to compensate for the low power indication, the bias current will stop increasing when it reaches BIASMAX value and continues to operate at that maximum value and TXFAULT asserted high. BIASMAX also controls the bias current when the circuit is operating in the open loop mode. Interfacing the Driver with the Laser Diode As shown in the “Typical Application” drawing, MOD+ pin is connected to the laser cathode through a 10Ω resistor and MOD- pin is connected to VCC with a 15Ω resistor equivalent to 10Ω (damping resistor) in series with the laser (equivalent resistor of 5Ω). The laser can be driven differentially by connecting MOD- to the anode of the laser through 15Ω (15Ω pull-up removed) and isolating the anode of the laser from VCC with an inductor. For better results at 2.5Gbps, the driver can be ACcoupled to the laser as shown in Figure 1. Figure 1. Laser AC-Coupled to the Driver Typical Application March 2008 7 M9999-030708-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Typical Characteristics Functional Characteristics March 2008 8 M9999-030708-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Input and Output Stages Figure 2a. Simplified Input Stage Figure 2b. Simplified Output Stage Interfacing DIN Input to Different Logic Drivers Figure 3a. Driving DIN with PECL Outputs March 2008 Figure 3b. Driving DIN with CML Outputs 9 M9999-030708-A [email protected] or (408) 955-1690 Micrel, Inc. SY88212L Package Information 24-Pin (3mm x 3mm) QFN 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. © 2008 Micrel, Incorporated. March 2008 10 M9999-030708-A [email protected] or (408) 955-1690