Preliminary Information MC2042-4 LED/Laser Driver Data Sheet Features Description Applications Pin Descriptions Measurement Tables Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Inc, Proprietary and Confidential May 2001 MC2042-4 LED/Laser Driver TABLE OF CONTENTS Current Switch ............................................................................................................................................................. 6 LED Drive and Temperature Compensation ............................................................................................................... 6 Pre-emphasis or `peaking'........................................................................................................................................... 6 LED clamping, Laser driving ....................................................................................................................................... 6 LED drive Pulse Width Adjust (PWA).......................................................................................................................... 6/7 Temperature Compensation Contour Plots................................................................................................................. 7 Typical Performance Curves (diagrams) ............................................................................................................... 8 Typical Performance Curves (diagrams) ............................................................................................................... 9 Functional Block Diagram ..................................................................................................... 10 Typical Applications Circuit .................................................................................................. 10 Bare Die Pad Co-ordinates ................................................................................................... 11 Disclaimer ............................................................................................................................... 12 World Wide Sales Offices ...................................................................................................... 13 Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 2 of 13 Preliminary Information Features .................................................................................................................................. 3 Applications ............................................................................................................................ 3 Connections............................................................................................................................ 3 General Description ............................................................................................................... 3 Ordering Information.............................................................................................................. 3 Top Level Diagram ................................................................................................................. 3 Pin Descriptions ..................................................................................................................... 4 Absolute Maximum Ratings .................................................................................................. 5 DC Electrical Characteristics ................................................................................................ 5 AC Electrical Characteristics ................................................................................................ 5 Signal Path Description ......................................................................................................... 6 MC2042-4 LED/Laser Driver GENERAL DESCRIPTION Data rates to >300 Mbps, depending on LED Single chip solution, available as die or in TSSOP20.or QSOP16 Fabricated in deep submicron CMOS for lowest cost & power consumption and long term reliability. Programmable output current from 5 mA to 100 mA. RC programmable pre-emphasis or `peaking' circuit giving drive current rise and fall times <500 ps Resistor programmable compensation for temperature dependence of LED output power. PECL input with optional Pulse Width Adjust. VREF voltage generator and output pin. Supports most LED types (e.g. 660 to 1300 nm) Single +5 V to +3.3 V operation. The MC2042-4 is a full custom CMOS IC designed for high-speed LED drive in low-cost optical fibre based transmission systems. Depending on the LED used, data rates to >300Mbps can be achieved. APPLICATIONS FDDI Fast Ethernet Fibre Channel OC3/STM1 The LED drive current is set by a resistor. To improve LED `on' time, a pre-emphasis circuit is included, which may be set via a simple RC network. To minimise the effects of temperature on LED output power, LED drive temperature compensation can be set by resistor over a 500 - 10,000 ppm/C range. Differential positive-ECL (PECL) data on the input pins can be shaped, if desired, by the differential voltage on the Pulse Width Adjust (PWA) pins. This adjustment is continuous over a 500 ps range. In addition, the VREF output pin allows single-ended input to the MC2042 and provides compatibility with industry-standard FO modules. ORDERING INFORMATION CONNECTIONS Fig.1 TSSOP20 NC PWAPWA- 1 20 NC 2 19 GND 3 18 GND DIN 4 17 IOUT 16 IOUT 15 IOUT Microcosm MC2042-4 Datecode DIN 5 VREF 6 RESET2 7 14 PEAK RTSET 8 13 VDD2 VDD1 9 12 VDD2 NC 10 11 NC Part Pin-Package MC2042-4DIE Waffle pack MC2042-4DIEW Expanded Whole Wafer on a ring MC2042-4Q16 QSOP16 MC2042-4T20 TSSOP20 TOP LEVEL DIAGRAM Fig. 2 6.5X4.4mm TSSOP Package QSOP16 DIN PWA- 1 16 GND DIN PWA+ 2 15 GND PWA DIN 3 14 IOUT PWA DIN 4 13 IOUT 12 IOUT Microcosm MC2042-4 Datecode VDD2 VDD1 VREF 5 RTSET2 6 11 PEAK RTSET 7 10 VDD2 VDD1 8 9 VDD2 IOUT PEAK IOUT Input Data Pulse Shaping Current Switch and Peaking Control VREF Generator Programmable Current Sink VREF GND GND2 RTSET RTSET2 4.3X3.9mm QSOP Package Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 3 of 13 Preliminary Information FEATURES MC2042-4 LED/Laser Driver PIN DESCRIPTIONS QSOP16 PIN NAME 1 - NC 2 1 PWA Inverse pulse width adjust input. 3 2 PWA Differential pulse width adjust input. Allows continious adjustment of input data pulse width 4 3 DIN+ Differential data input 5 4 DIN- Inverse differential data input 6 5 VREF Reference output. Can be used with single-ended data input 7 6 RTSET2 Temperature compensation adjustment pin. Allows temperature dependance of LED light output to be reduced or removed 8 7 RTSET Sets nominal LED drive current 9 8 VDD1 Power pin, connect to most positive supply 10 - NC Not connected 11 - NC Not connected 12, 13 9, 10 VDD2 LED shorting pin, connect to most positive supply. Speeds LED switch off 14 11 PEAK Connection for pre-emphasis or peaking circuit 15, 16 12, 13 IOUT Driver output. Connect LED between this pin and VDD 17 14 IOUT Logical inverse of pin 8. Connect resistor of approximately the same value as LED (at the programmed drive current level) between this pin and VDD 18, 19 15,16 GND Ground pin. Connect to the most negative supply 20 - NC Preliminary Information - REV _D Description Not connected Not connected Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 4 of 13 Preliminary Information TSSOP20 PIN MC2042-4 LED/Laser Driver ABSOLUTE MAXIMUM RATINGS Symbol Parameter Total power dissipation (TSSOP20) VCC Power supply (VCC-GND) Units 255 mW 7 V 150 C TJ Junction temperature TA Operating ambient -40 to +85 C Storage temperature -65 to +50 C TSTG These are the absolute maximum ratings at or beyond which the IC can be expected to fail or be damaged. Reliable operation at these extremes for any length of time is not implied. DC ELECTRICAL CHARACTERISTICS Symbol Parameter Min Typ Max Units VIN_H PECL high input level VCC-1.0 - VCC V VIN_L PECL low input level VCC-2.0 - VCC-1.8 V VREF Voltage reference VCC-1.6 VCC-1.4 VCC-1.03 ILED'ON LED drive current 5 - 120 mV ILED'OFF LED off current - - 50 A ICOMP LED drive current temperature compensation range 0.05 - 1 %/C VLEDH LED headroom voltage - - VDD-2.0 V AC ELECTRICAL CHARACTERISTICS Symbol Parameter Min Typ Max Units FC Maximum data rate 300 - - Mbps TPWA Input data pulse width adjust range -500 - 500 ps LED tR LED drive rise time - 0.7 1 ns LED tF LED drive fall time - 0.7 1 ns IPEAK Peaking current (as % of LED drive current) 0 - 50 % PEAK tR Peaking current rise time - - 1 ns PEAK tF Peaking current fall time - - 1 ns PEAK tD Peaking current decay time - C1X(R4+5) - S IDD Supply current - ILED+10 ILED+20 mA Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 5 of 13 Preliminary Information PTOT Rating MC2042-4 LED/Laser Driver SIGNAL PATH DESCRIPTION Current Switch LED Drive and Temperature Compensation The two resistors R1 and R2 set the LED drive current and temperature compensation. The simplified application diagram (Fig. 6) shows R1 connected between RTSET and GND, and R2 between RTSET and the RTSET2 pin. The current flowing out of the RTSET pin determines the LED drive current. The temperature independent component of the LED drive current is set mainly by R1. The temperature dependent component is set mainly by R2. However, R1 and R2 are not independent. The RTSET2 pin connects to an internal diode on the IC, which exhibits standard diode behaviour with temperature. As temperature rises, the voltage on the diode drops, the current flowing through R2 increases and the LED drive current increases. Given the various interdependencies of the drive current, R1, R2, and temperature compensation, the relationships have been plotted as contour plots (see Temperature Compensation Contour Plots). Please contact MindspeedTM if other combinations are required. The LED `on' current is controlled to 5 %. Pre-emphasis or `peaking' To improve LED `turn on' time an optional pre-emphasis function is included on the MC2042-4. If this is not required, then the PEAK pin should be left floating. Two external components (R4, C1) are required to implement peaking. As shown in Fig. 6. When the LED is turned off, the voltage on PEAK is pulled HIGH rapidly. This voltage transient is coupled through R4 and C1 and exerts a transient current in the opposite direction on the LED. . The transient current amplitude and RC decay are given approximately by: Peak current (Amps): 4/(R4 + 5) Decay (seconds): C1 x (R4 + 5) The above approximations assume an ideal LED model with 0 Ohms resistance. Real LEDs will slightly alter the peaking effect. Typical values for R4 and C1 are: R4 = 50 Ohms C1 = 20 pF LED clamping, Laser driving Since most LEDs exhibit a longer `turn off' time than `turn on' time, a clamping function is included on the MC2042 in order to reduce the `turn off' time. Clamping is effected via the two VDD2 connections. The disadvantage of clamping is that the LED's internal capacitance has to be fully charged again before the LED starts to emit light. This delayed `turn on' effect becomes noticeable when the nominal LED drive current is low. Use of the peaking circuit helps solve this problem. Thus, the combination of peaking and clamping results in very fast `turn on' and `turn off' times for the LED. When driving Lasers, it will often be helpful to disable this clamping. This can be achieved by leaving the VDD2 connections floating. VDD1 must still be connected. LED drive Pulse Width Adjust (PWA) The input pulse width can be adjusted prior to application to the LED switch. The differential voltage on the PWA (Pulse Width Adjust) pins shapes the input pulse linearly over a nominal -500 to +500 ps range, according to the formula: Delta PW (ps) = K x VPWA Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 6 of 13 Preliminary Information Differential Positive-ECL (PECL) data on the data input pins controls the LED current switch. The LED current flows either through the LED or via the dummy load so that VDD noise is minimised. To reduce LED `turn-off' time, the LED is momentarily short-circuited, via VDD2, before the current is switched to the dummy load. When the LED is turned on, the voltage on PEAK is pulled LOW very rapidly. This voltage transient is coupled through R4 and C1 and exerts a transient current on the LED. MC2042-4 LED/Laser Driver The following table shows an example at VCC = 3.3 V Where: K = 500 100 Ambient VPWA = (VPWA+) - (VPWA-) The maximum range for VPWA is 1V. The input impedance is 3.6 k. VPWA+ and VPWA- will settle at a nominal voltage equal to (0.6 * VDD) if left floating. It is recommended that adjustment be implemented by pull down resistors on PWA+ or PWA-. However, it is common for one or other pin to be tied to ground as a zero-cost, `gross' adjustment. If pulse width adjustment is not required PWA+ and PWAshould be tied to ground. Temperature Compensation Contour Plots. On the following page there are two contour graphs at junction temperatures of 50C and 125C showing R1 from 2k2 to 330 k along the y-axis and R2 from 220 to 82 k along the x-axis. The labels on the contours are the led currents (ILED). Choose the contours that represent the required ILED at the two different die temperatures, superimpose the two graphs. Where the two contours cross gives the R1/R2 value. 25 85 C ILED 70 100 mA VLED 1.5 1.5 V PSTATIC 50 50 mW PDYNAMIC (VCCVLED)x(70)=245 RT 100 100 C/watt TJ TA+24.5+5=54.5 85+35+5=125 C Looking at the intersection of the relevant curves on pages 8/9: log10 (R1) = 4.18 R1 = 15 k log10 (R2) = 3.33 R2 = 2.2 k There are two further contour plots at junction temperatures of 75C and 100C. These can be used in a similar manner to choose values of R1 and R2. NOTE: the contour graphs are based on MC2042-4 junction temperatures (Tj), at 50 and 125C. The user must take into account the power dissipation and thermal resistance to arrive at the die temperature. Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 7 of 13 Preliminary Information and MC2042-4 LED/Laser Driver TYPICAL PERFORMANCE CURVES Preliminary Information log 10 R1 Fig. 3 log 10 R2 Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 8 of 13 MC2042-4 LED/Laser Driver TYPICAL PERFORMANCE CURVES Preliminary Information Fig. 4 Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 9 of 13 MC2042-4 LED/Laser Driver FUNCTIONAL BLOCK DIAGRAM VDD2 VDD1 DIN DIN IOUT IOUT PEAK Input Data Pulse Shaping Current Switch and Peaking Control VREF Generator Programmable Current Sink PWA PWA VREF GND GND2 RTSET2 RTSET TYPICAL APPLICATIONS CIRCUIT Fig. 6 VCC LED Dum m y LED Load R4 VDD1 D IN D IN V DD2 In p u t D a ta P u ls e S h a p in g IO U T C1 IO U T PEAK C u r r e n t S w itc h a n d P e a k in g C o n tr o l PW A PW A V REF V R E F G e n e r a to r GND GND2 P r o g r a m m a b le C u r r e n t S in k R T SET R T SET2 R2 R1 Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Page 10 of 13 Preliminary Information Fig. 5 MC2042-4 LED/Laser Driver BARE DIE PAD CO-ORDINATES Description X Y 1 VREF -73 394.5 2 RTSET2 -219 394.5 3 RTSET -397 214.7 4 VDD1 -397 68.7 5 VDD2 -397 -77.3 6 VDD2 -397 -223.3 7 PEAK -219 -394.5 8 IOUT -73 -394.5 9 IOUT 73 -394.5 10 IOUT 219 -394.5 11 GND 397 -223.3 12 GND 397 -77.3 13 PWA- 397 68.7 14 PWA+ 397 214.7 15 DIN 219 394.5 16 DIN 73 394.5 Preliminary Information - REV _D Information provided in this Data Sheet is ADVANCED and is subject to change without notice. MindspeedTM Technologies, Proprietary and Confidential Preliminary Information Pad Page 11 of 13 MC2042-4 LED/Laser Driver DISCLAIMER Information in this document is provided in connection with Mindspeed Technologies. "Mindspeed" products. These materials are provided by Mindspeed as a service to its customers and may be used for informational purposes only. 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