L2042A ALSC | Alldatasheet

Document overview

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Technical content

Features

§ FCC approved method of EMI attenuation. § Provides up to 15dB of EMI suppression. § Generates a low EMI spread spectrum clock of the input frequency. § Input frequency range: 30MHz to 75 MHz. § Optimized for 32.5MHz, 54MHz, and 65MHz. § Internal loop filter minimizes external components and board space. § Selectable spread deviation. § SSON# control pin for spread spectrum enable and disable options. § Low cycle-to-cycle jitter. § 2.5V or 3.3V operating voltage range. § TTL or CMOS compatible outputs. § Ultra-low power CMOS design. § Supports most mobile graphic accelerator and LCD timing controller specifications. § Available in 8-pin SOIC and TSSOP. Product Description The L2042A is a versatile spread spectrum frequency modulator designed sp ecifically for digital falt panel applications. The L2042A reduces electromagnetic interference (EMI) at the clock source, allowing system wide reduction of EMI of down stream clock and data dependent signals. The L2042A allows significant system cost sav ings by reducing the number of circuit board layers ferrite beads, shielding and other passive components that are traditionally required to pass EMI regulations. The L2042A uses the most efficient and optimized modulation profile approved by the FCC and is implemented in a proprietary all digital method. The L2042A modulates the output of a single PLL in order to “spread” the bandwidth of a synthesized clock, and more importantly, decreases the peak amplitudes of its harmonics. This results in signifi cantly lower system EMI compared to the typical narrow band signal produced by oscillators and most frequency generators. Lowering EMI by increasing a signal’s bandwidth is called ‘spread spectrum clock generation’.

Applications

The L2042A is targeted t owards digital flat panel applications for Notebook PCs, Palm -size PCs, office automation equipment, and LCD monitors. Block Diagram VSS CLKIN Frequency Divider Feedback Divider Modulation Phase Detector Loop Filter VCO Output Divider MODOUT PLL VDD SSON# DIV2 SR0 CP0 CP1

rev 1.0 2.5V LCD Panel EMI Reduction IC 2 of 10 4 5 L2042A XIN /CLK CP0 CP1 VSS SSON# ModOUT SR0 VDD Pin Configuration Pin Description Pin# Pin Name Type Description 1 CLKIN I External reference frequency input. Connect to an externally generated reference signal. 2 CP0 I Digital logic input used to select charge pump current. Refer Modulation Selection Table. This pin has an internal pull -up resistor. 3 CP1 I Digital logic input used to select charge pump current. Refer Modulation Selection Table. This pin has an internal pull -up resistor. 4 VSS P Ground to entire chip. Connect to system ground.

6 SSON# I

Digital logic input used to enable Spread Spectrum function (Active LOW). Spread Spectrum function enabled when LOW, disabled when HIGH. This pin has an internal pull -low resistor. 7 ModOUT O Spread spectrum clock output.

5 SR0 I Digital logic input used to select Spreading Range Refer Modulation

Selection Table. This pin has an i nternal pull-up resistor. 8 VDD P Power supply for the entire chip (+2.5V or 3.3V) Modulation Selection Table Spreading Range ( ±± %) CP0 CP1 SR0 32.5MHz 54MHz 65MHz 70MHz Modulation Rate 0 0 0 0.49 0.92 0.88 0.87 0 0 1 1.71 1.48 1.37 1.32 0 1 0 1.2 0.92 0.88 0.84 0 1 1 1.69 1.48 1.37 1.33 1 0 0 1.09 0.71 0.58 0.42 1 0 1 1.68 1.14 0.9 0.73 1 1 0 0.8 0.4 0.3 0.25 1 1 1 1.29 0.62 0.48 0.37 (FIN/40) * 62.49 KHz

rev 1.0 2.5V LCD Panel EMI Reduction IC 3 of 10 CLKIN CP0 CP1 VSS SR0 SSON# ModOUT VDD L2042A Spread Spectrum The Modulation S election Table illustrates the possible spread spectrum options. The optimal setting should minimize system EMI to the fullest withou t affecting system performance. The spreading is described as a percentage deviation of the center frequency (Note: The center frequency is the frequency of the external reference input on CLKIN, Pin1). Example: The L2042A is designed f or high-resolution flat panel applications and is able to support panel frequencies from 30 to 75 MHz. For a 65MHz pixel clock frequency, a spreading sel ection of CP0=0 and CP1=1 and SR0=1 gives a percentage deviation of TBD%. Refer Modulation Selection Table. This results in frequency on Mo dOUT being swept from TBD to TBD MHz. This particular example (See figure below) given here is a common EMI reduction method for notebook LCD panel and has already been i mplemented by most of the leading OEM and mobile graphic accelerator manufacture rs.

65 MHz from Graphics Accelerator

with 1.5% deviation and modulation rate of 50.77KHz. This signal is connected back to the spread spectrum input pin (SSIN) of the graphics accelerator VDD 0.1µF Digital control for SS Enable or Disable

rev 1.0 2.5V LCD Panel EMI Reduction IC 4 of 10 EMC Software Simula tion By using Alliance’s proprietary EMC simulation software – EMI -Lator®, radiated system level EMI analysis can be made easier, allowing quantitative measure on the benefits of Alliance’s EMI reduction products. The simulation engine of this EMC softwar e has already been characterized to correlate with the electrical characteristics of Alliance EMI reduction ICs. The figure below is an illustration of this simulation result. Please visit our website at www.alsc.com for information on how to obtain a free copy and demonstration of EMI-Lator ®. Simulation results From EMI -Lator®

rev 1.0 2.5V LCD Panel EMI Reduction IC 5 of 10 Absolute Maximum Ratings Symbol Parameter Rating Unit VDD, VIN Voltage on any pin with respect to GND -0.5 to + 7.0 V TSTG Storage temperature -65 to +125 °C TA Operating temperature 0 to 70 °C Note: These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliability. Symbol Parameter Min Typ Max Unit VIL Input low voltage GND – 0.3 - 0.8 V VIH Input high voltage 2.0 - VDD + 0.3 V IIL Input low current (pull -up resistors on inputs SR0, SR1, CP0 and CP1) - - -35 µA IIH Input high current (pull -down resistor on input SSON#) - - 35 µA VOL Output low voltage (V DD = 3.3V, IOL = 20mA) - - 0.4 V VOH Output high voltage (V DD = 3.3V, IOH = 20mA) 2.5 - - V ICC Dynamic supply current normal mode (2.5 V, and 15pF loading) TBD @ 30MHz - TBD @70MHz mA IDD Static supply current standby mode - 0.6 - mA VDD Operating voltage 2.25 2.85 3.7 V tON Power up time (first locked clock cycle after power up) - 0.18 - mS ZOUT Clock output impedance - 50 -

rev 1.0 2.5V LCD Panel EMI Reduction IC 6 of 10 Symbol Parameter Min Typ Max Unit fIN Input frequency 30 - 75 MHz fOUT Output frequency 30 - 75 MHz tJC Jitter (cycle to cycle) - - 360 ps tD Output duty cycle 40 50 55 % *tLH and tHL are measured into a capacitive load of 15pF

rev 1.0 2.5V LCD Panel EMI Reduction IC 7 of 10 D E H D A2 A θ L C B e

Package Information

Symbol Dimensions in inches Dimensions in millimeters Min Max Min Max A 0.057 0.071 1.45 1.80 A1 0.004 0.010 0.10 0.25 A2 0.053 0.069 1.35 1.75 B 0.012 0.020 0.31 0.51 C 0.004 0.01 0.10 0.25 D 0.186 0.202 4.72 5.12 E 0.148 0.164 3.75 4.15 e 0.050 BSC 1.27 BSC H 0.224 0.248 5.70 6.30 L 0.012 0.028 0.30 0.70 è 0° 8° 0° 8°

rev 1.0 2.5V LCD Panel EMI Reduction IC 8 of 10 E H A D B C L θ e 8-Pin TSSOP Dimensions in inches Dimensions in millimeters Symbol Min Max Min Max A 0.047 1.10 A1 0.002 0.006 0.05 0.15 A2 0.031 0.041 0.80 1.05 B 0.007 0.012 0.19 0.30 C 0.004 0.008 0.09 0.20 D 0.114 0.122 2.90 3.10 E 0.169 0.177 4.30 4.50 e 0.026 BSC 0.65 BSC H 0.244 0.260 6.20 6.60 L 0.018 0.030 0.45 0.75 è 0° 8° 0° 8°

rev 1.0 2.5V LCD Panel EMI Reduction IC 9 of 10 Ordering Codes Part Number Marking Package type Qty/reel Temperature L2042A-08ST L2042A 8 PIN SOIC, TUBE 0°C To 70°C L2042A-08SR L2042A 8-PIN SOIC, TAPE AND REEL 2,500 0°C To 70°C L2042A-08TT L2042A 8-PIN TSSOP, TUBE 0°C To 70°C L2042A-08TR L2042A 8-PIN TSSOP, TAPE AND REEL 2,500 0°C To 70°C

rev 1.0 2.5V LCD Panel EMI Reduction IC 10 of 10 © Copyright 2003 Alliance Semiconductor Corpo ration. All rights reserved. Our three -point logo, our name and Intelliwatt are trademarks or registered trademarks of Alliance. All other brand and product names may be the trademarks of their respective companies. Alliance reserves the right to make chan ges to this document and its products at any time without notice. Alliance assumes no responsibility for any errors that may appear in this document. The data contained herein represents Alliance's best data and/or estimates at the time of issuance. Allian ce reserves the right to change or correct this data at any time, without notice. If the product described herein is under development, significant changes to these specifications are possible. The information in this product data sheet is intended to be g eneral descriptive information for potential customers and users, and is not intended to operate as, or provide, any guarantee or warrantee to any user or customer. Alliance does not assume any responsibility or liability arising out of the application or use of any product described herein, and disclaims any express or implied warranties related to the sale and/or use of Alliance products including liability or warranties related to fitness for a particular purpose, merchantability, or infringement of any intellectual property rights, except as express agreed to in Alliance's Terms and Conditions of Sale (which are available from Alliance). All sales of Alliance products are made exclusively according to Alliance's Terms and Conditions of Sale. The purchase of products from Alliance does not convey a license under any patent rights, copyrights; mask works rights, trademarks, or any other intellectual property rights of Alliance or third parties. Alliance does not authorize its products for use as critical components in life -supporting systems where a malfunction or failure may reasonably be expected to result in significant injury to the user, and the inclusion of Alliance products in such life -supporting systems implies that the manufacturer assumes all risk of such use and agrees to indemnify Alliance against all claims arising from such use. Alliance Semiconductor Corporation 2595, Augustine Drive, Santa Clara, CA 95054 Tel# 408-855-4900 Fax: 408-855-4999 www.alsc.com Copyright © Alliance Semiconductor All Rights Reserved Preliminary Information Part Number: L2042A Document Version: v1.0