sy88422l

4.25Gbps Laser Driver with Integrated Bias

General Description

Features

• • • • •

35mA power supply current typical Operation up to 4.25Gbps

Modulation current up to 90mA Bias current up to 100mA

Available in 16-pin small form factor (3mm x 3mm) QFN package

The SY88422L is a single 3.3V supply, small form factor laser driver for telecom/datacom applications up to 4.25Gbps. The driver can deliver modulation current up to 90mA and a bias current up to 100mA.

Datasheets and support documentation can be found on Micrel’s web site at: www.micrel.com.

Applications

• Multi-rate LAN, MAN applications up to 4.25Gbps: FC, GbE, SONET/SDH • SFF, SFP, LX-4 Modules

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Typical Application

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Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

Micrel, Inc. SY88422L

Ordering Information(1)

Part Number SY88422LMG SY88422LMGTR Notes:

1. Contact factory for die availability. Dice are guaranteed at TA = +25°C, DC Electricals only. 2. Tape and Reel.

(2)Package Type QFN-16 QFN-16 Operating Range Industrial Industrial Package Marking 422L with Pb-Free bar-line indicator 422L with Pb-Free bar-line indicator Lead Finish NiPdAu Pb-Free NiPdAu Pb-Free

Pin Configuration

16-Pin QFN

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Pin Description

Pin Name 1, 4, 9, 12 7, 8, 14 2 3 5 6 10 11 13 15 16 Pin Number VCC GND DIN+ DIN– MODSET /EN MOD– MOD+ BIAS BIASMON BIASSET Pin Function Supply Voltage. Bypass with a 0.1µF//0.01µF low ESR capacitor as close to VCC pin as possible. Ground. Ground and exposed pad must be connected to the plane of the most negative potential. Non-inverting input data. Internally terminated with 50Ω to a reference voltage. Inverting input data. Internally terminated with 50Ω to a reference voltage. Modulation current setting and control. The voltage applied to this pin will set the modulation current. Input impedance 25kΩ. Active Low TTL. The driver is disabled when this pin is unconnected or /EN asserted high. The driver is enabled when /EN is asserted low. Inverted modulation current output. Outputs modulation current when input data is negative. Non-inverted modulation current output. Outputs modulation current when input data is positive. BIAS Current Output Bias monitor. Install an external resistor from this pin to GND to convert the output current to a voltage proportional to the bias current Bias current setting. The voltage applied to this pin will set the bias current. Input impedance 25kΩ.

Truth Table

DIN+ L H X Notes:

1. IMOD = 0 when MOD+ = H.

2. Assuming that the laser cathode is tied to MOD+.

DIN- H L X /EN L L H or NC MOD+H L H (1) MOD- L H L Laser OutputL H L (2)

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Absolute Maximum Ratings(1)

Supply Voltage (VCC) .................................... –0.5V to +4.0V

VCC–1.2V to VCC+0.5V CML Input Voltage (VIN) ....................

TTL Control Input Voltage (VI)............................... 0V to VCC Lead Temperature (soldering, 20sec.) ..................... +260°C Storage Temperature (Ts) ......................... –65°C to +150°C

Operating Ratings(2)

Supply Voltage (VCC) .................................... +3.0V to +3.6V Ambient Temperature (TA) .......................... –40°C to +85°C

(3)

Package Thermal Resistance QFN

........................................................ 60°C/W (θJA) Still-air

(ψJB) ................................................................... 33°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 = 30mA, IBIAS = 20mA.

Symbol ICC VMOD_C VBIAS_C RIN(DATA) VDIFF_IN (DIN) VIL (/EN) VIH (/EN) RIN (MODSET) VMODSET RIN (BIASSET) VBIASSET 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 = 56mA for worst-case conditions with IMOD = 90mA and BIAS=100 mA, TA = +85°C, VCC = 3.6V.

Parameter Power Supply Current Compliance Voltage Compliance Voltage Input Resistance at DIN+, DIN-, Single Ended Differential Input Voltage Swing Input Low Voltage Input High Voltage MODSET Input Resistance Voltage Range on MODSET Pin BIASSET Input Resistance Voltage Range on BIASSET Pin Condition Modulation currents excluded IMOD range 10mA to 90mA IBIAS range 10mA to 100mA Min VCC-1.5 VCC-2.3 45 100 2 Typ 35 50 25 25 Max 56 VCC VCC 55 2400 0.8 1.2 1.2 (4)Units mA V V Ω mVpp V V kΩ V kΩ V

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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 = 30mA, IBIAS = 20mA.

Symbol IMOD IMOD_OFF tr tf Parameter Data Rate Modulation Current Modulation OFF Current Output Current Rise Time Output Current Fall Time Total Jitter Bias Current Bias OFF Current (5)(5)Condition NRZ Laser or equivalent load AC-coupled to the driver Current at MOD+ and MOD- when the device is disabled 20% to 80%, 15 Ω load 20% to 80%, 15 Ω load Current at BIAS when the device is disabled Min 0.1 10 5 Typ 50 50 Max 4.25 90 150 70 70 20 100 150 Units Gbps mA µA ps ps psPP mA µA IBIAS IBias_OFF Notes:

5. Load = 15Ω.

Test Circuit

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Typical Characteristics

Functional Characteristics

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Functional Block Diagram

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Input and Output Stages

Figure 1a. Simplified Input Stage Figure 1b. Simplified Output Stage

Interfacing the Input to Differential Logic Drivers

Figure 2a. AC-Coupling to LVPECL Driver Figure 2b. AC-Coupling to CML Driver

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current and zero ohm (0Ω) path for the DC current offering headroom for the driver equal to VCC and almost all the modulation current goes into the laser. The inductor alone will cause signal distortion, and, to improve that, a combination of resistor and inductor can be used as shown in Figure 3. In this case, the headroom of the driver is VCC – R1 * αImod, where αImod is the portion of the modulation current that goes through the pull-up network.

The coupling capacitor creates a low-frequency cutoff in the circuit, and its value must be chosen to accommodate the lowest and the highest data rates. If the value of the cap is too high, it will degrade the performance at higher data rates, and, if its value is too small, it won’t be able to hold a constant charge between the first bit and the last bit of a long string of identical bits in a low data rate application. This leads in both cases to higher pattern-dependant jitter in the transmitter signal. 0.01µ-to-0.1µF is found to be good range for all applications from 155Mbps to 4.25Gbps.

Application Hints

The typical applications drawing on the front page shows how to connect the driver to the laser differentially. To drive the laser single ended, just disconnect MOD- from the laser anode and pull it up to VCC with a resistor equal to the equivalent resistor of the load on MOD+, damping resistor plus the laser equivalent resistor. Differential drive improves transition time and laser response. Driving the laser differentially will also minimize the cross talk with the rest of the circuitry on the board especially the receiver.

If we refer to Figure 3, the modulation current out of the driver is split between the pull-up network and the laser. If, for example, the total pull-up resistor is twice the sum of the damping resistor and laser equivalent series resistance, only two thirds (2/3) of the modulation current will be used by the laser. To keep most of the modulation current going through the laser, try to keep the total pull-up resistors as high as possible. One solution consists in using an inductor alone as pull-up, presenting a high impedance path for the modulation

Figure 3. AC-Coupling the Laser to the Driver

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Package Information

16-Pin 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. © 2007 Micrel, Incorporated.

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