M02042G-4D03-T

Preliminary Information This document contains information on a new product. The parametric information, although not fully characterized, is the result of testing initial devices. MC2042-4 LED/Laser Driver for FDDI, Fast Ethernet, Fibre Channel, OC3/STM-1, IEEE1394 The MC2042-4 is a CMOS IC designed for high-speed LED drive in low-cost optical fiber based transmission systems. Depending on the LED used, data rates to >300 Mbps can be achieved. 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 minimize 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. Features • FDDI, Fiber Channel • Fast Ethernet, IEEE1394 • OC3/STM1 • Data rates to >300 Mbps, depending on LED • Single chip solution, available as die or in TSSOP20 or QSOP16 fabricated in deep sub-micron CMOS for lowest cost & power consumption and long term reliability • Programmable output current from 5 mA to 120 mA • RC programmable pre-emphasis or ‘peaking’ circuit giving drive current rise and fall times 300 Mbps can be achieved. 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. 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. 3.1.1 Signal Path Description 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 minimized. To reduce LED ‘turn-off’ time, the LED is momentarily short-circuited, via VDD2, before the current is switched to the dummy load. 3.1.2 LED Drive and Temperature Compensation The LED drive current and temperature compensation is set by the two resistors R1 and R2. The simplified application diagram (Figure 3) 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 primarily by R1. The temperature dependent component 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 tabulated (see Temperature Compensation table). Please contact Mindspeed if other combinations are required. The LED 'on' current is controlled to ±5%. 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 5 Preliminary Information To minimize 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. Functional Description A Microsoft Excel file is available from Mindspeed which will calculate appropriate values for RTSET resistors R1 and R2 given your LED current, forward voltage, and LED temperature coefficient. The file may be obtained from a Mindspeed Field Applications Engineer and is named 'MC2042-4 resistor selection.xls'. Figure 3-1. LED Drive and Temperature Compensation RTSET RTSET2 (unused) R2 ExternalDiode for Temp. Comp. R1 Transmit Enable/Disable There is no dedicated pin on the MC2042 to disable the LED drive current. However, the LED drive current can be disabled by disabling the current out of pin RTSET. The LED current is approximately 100x the current out of pin RTSET, so if the current out of this pin is 0, the LED drive current is 0. However, if peaking is used the peaking current will not be disabled. Figure 3-2 illustrates how the current out of RTSET can be disabled by adding a MOSFET (Q1) at the RTSET node of the R1/R2 temperature compensation network. The voltage on the gate of Q1 then controls transmit enable/disable. When selecting Q1, a MOSFET should be chosen with an Rds(on) which is negligible compared to R1 and R2. Figure 3-2. Transmit Enable/Disable RTSET RTSET2 Transmit Enable R2 R1 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 6 Preliminary Information 3.1.3 Functional Description 3.1.4 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 as shown in Figure 4-1 to implement peaking. 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. 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: 50 Ω C1 = 20 pF 3.1.5 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 enabled 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. 3.1.6 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 Where: K = 500 ± 100 and VPWA = (VPWA+) - (VPWA-) The maximum range for VPWA is ±1V. The input impedance is 3.6 kΩ. 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. 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 7 Preliminary Information R4 = Functional Description If pulse width adjustment is not required PWA+ and PWA- should be tied to ground. 3.1.7 Eye Diagram The eye diagram below is typical of the electrical output of the MC2042-4. The crossover point can be moved up and down using the PWA pin. The overshoot can be increased by using the PEAK pin. Figure 3-3. Eye Diagram Preliminary Information 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 8 4.0 Applications Information 4.1 Typical Applications Circuit Figure 4-1. Typical Applications Circuit VCC Preliminary Information LED Dummy LED Load Optional Peaking R4 C1 VDD1 DIN DIN VDD2 IOUT IOUT PEAK Input Data Pulse Shaping Current Switch and Peaking Control VREF Generator Programmable Current Sink PWA PWA VREF GND GND2 RTSET R2 RTSET2 R1 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 9 Preliminary Information/Mindspeed Proprietary and Confidential Mindspeed Technologies™ A B C D 1 1 0V HD1 3.3V 1 2 3 POWER SK5 DATA_INB SK4 DATA_IN DATA INPUTS SK6 1 DATA_CMOS 2 02042-DSH-001-D 2 1 + C10 10UF EXCCL3216U L2 R5 50R C7 100NF VCC1 R14 N/C R13 N/C VCC1 C9 100NF VCC2 C11 10NF R6 50R 100NF R8 N/C EXCCL3216U L1 C5 C6 100NF N/C R9 C12 10NF VCC1 R16 N/C R15 N/C R17 50K R10 1K R19 50K R7 10K R18 50K 2 3 C1 10NF VCC1 VBB 10 9 8 7 6 5 4 3 2 1 IC1 N/C N/C VDD2 VDD2 PEAK IOUT IOUT IOUTB GND GND 20 11 12 13 14 15 16 17 18 19 3 TITLE MICROCOSM MC2042-4 N/C VDD1 RTSET RTSET2 VBB DIN- DIN+ PWA+ PWA- N/C These pots can be altered to give a total of +/- 500 pS Pulse width adjustment. No adjustment occurs if PWA + & PWA- are tied to gnd. Maximum adjustment in either direction is obtained by connecting PWA+ to VCC and PWA- to gnd , or viceversa. Controls -------------Pulse width adjust - R17/R18 General ------------The board allows the user full flexibility for determining the resistor valuesrequired for the pulse width adjust, LED current and LED temperature compensation functions. This board is provided for evaluation of the MC2042-4 SET NOMINAL LED DRIVE CURRENT SET LED TEMP COMP R12 N/C R11 N/C LED PULSE WIDTH ADJUST VCC1 2 0R R1 R2 R3 R4 C2 10NF N/C N/C 22R VCC2 18PF C4 C8 100NF VCC2 SK3 SK2 SK1 4 SHEET OF 1 1 REV 1 DOC_NO MC2042 CAN_GND CATHODE ANODE LED INTERFACE MC2042-4 EVALUATION BOARD C3 10NF Inputs ----------SK4 & SK5 are provided for the connection of differential PECL input signals. Alternatively a CMOS input may be connected to SK6.If using SK6, remove R6, C5 & C6 and fit R8 & R9 with 1K resistors. The drive current and temperature compensation is determined by two potentiometers , R19 & R7 respectively .LED turn-on time can be improved by proper selection of R2, R3 & C4. Refer to Microcosm documentation for selection of these values. LED drive current & temp compensation - R19 & R7 4 A B C D Figure 4-2. 2 4.2 Preliminary Information 1 Applications Information Evaluation Board An electrical evaluation board is available for the MC2042-4. The schematic is shown below. Evaluation Board 10 5.0 Package Specification Figure 5-1. TSSOP20 Package Information Preliminary Information Note: This package is available in conventional, lead-free and RoHS-compliant versions. Consult the Mindspeed.com web site for current information. 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 11 Package Specification QSOP16 Package Information Table 5-1. TSSOP20 Dimensions Dims. Tols/leads TSSOP20L A MAX 1.20 A1 0.5MIN/.10MAX. A2 NOM .90 D ±.05 6.50 E ±.10 6.40 E1 ±.10 4.40 L +.15/-.10 .60 L1 REF. 1.00 Zp REF. .325 e BASIC .65 b ±.05 .22 c 02042-DSH-001-D Preliminary Information Figure 5-2. .13MIN/.20MAX e ±4° 4° aaa MAX. .10 bbb MAX. .10 ccc MAX .05 ddd MAX. .20 Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 12 Package Specification Table 5-2. Dims. Tols/N QSOP16 A MAX. 1.60 A1 ±.05 0.1 A2 ±.10 1.40 D ±.10 4.9 E ±.20 6.00 E1 ±.10 3.90 L ±.05 0.6 ccc MAX. 0.10 ddd MAX. 0.10 e BASIC 0.65 b ±.05 0.25 c ±.05 .2 Min. .24 Max. R ±.05 0.20 R1 Min. 0.20 Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential Preliminary Information 02042-DSH-001-D QSOP16 Dimensions 13 Information in this document is provided in connection with Mindspeed TechnologiesTM ("MindspeedTM") products. These materials are provided by Mindspeed as a service to its customers and may be used for informational purposes only. Except as provided in Mindspeed’s Terms and Conditions of Sale for such products or in any separate agreement related to this document, Mindspeed assumes no liability whatsoever. Mindspeed assumes no responsibility for errors or omissions in these materials. Mindspeed may make changes to specifications and product descriptions at any time, without notice. Mindspeed makes no commitment to update the information and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to its specifications and product descriptions. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this document. THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, RELATING TO SALE AND/OR USE OF MINDSPEED PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, CONSEQUENTIAL OR INCIDENTAL DAMAGES, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. MINDSPEED FURTHER DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. MINDSPEED SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS, WHICH MAY RESULT FROM THE USE OF THESE MATERIALS. Mindspeed products are not intended for use in medical, lifesaving or life sustaining applications. Mindspeed customers using or selling Mindspeed products for use in such applications do so at their own risk and agree to fully indemnify Mindspeed for any damages resulting from such improper use or sale. 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 14 Preliminary Information © 2005, Mindspeed Technologies, Inc. All rights reserved. www.mindspeed.com General Information: (949) 579-3327 Headquarters - Newport Beach 4000 MacArthur Blvd., East Tower Newport Beach, CA. 92660 Preliminary Information 02042-DSH-001-D Mindspeed Technologies™ Preliminary Information/Mindspeed Proprietary and Confidential 15