WM8255SEFL Cirrus Logic

WM8255 w Single Channel 16-bit CIS/CCD AFE with RGB LED Current Drive DESCRIPTION FEATURES The WM8255 is a 16-bit analogue front end/digitiser IC 16-bit ADC which processes and digitises the analogue output signals 12 MSPS conversion rate from CCD sensors or Contact Image Sensors (CIS) at pixel Low power 250 mW typical sample rates of up to 12 MSPS. 5.75V and 3.3V supply operation The device includes a complete signal processing channel Single channel operation containing Reset Level Clamping, Correlated Double Correlated double sampling Sampling, Programmable Gain and Offset adjust functions. Programmable gain (8-bit resolution) Internal multiplexers allow fast switching of offset and gain Programmable offset adjust (8-bit resolution) for line-by-line colour processing. The output from this channel is time multiplexed into a high-speed 16-bit Programmable clamp voltage Analogue to Digital Converter. The digital output data is RGB LED current drive using current and PWM available in a 2 bit or 4-bit wide multiplexed format. 2-bit or 4-bit wide multiplexed data output format An internal 4-bit DAC is supplied for internal reference level Internally generated voltage references generation. This may be used during CDS to reference CIS 28-lead QFN package signals or during Reset Level Clamping to clamp CCD 3 wire serial control interface signals. An external reference level may also be supplied. ADC references are generated internally, ensuring optimum APPLICATIONS performance from the device. Flatbed and sheetfeed scanners The device includes an RGB LED current drive using current USB compatible scanners and PWM functionality to control the operation of sensor Multi-function peripherals LEDs. The device typically uses an analogue supply voltage of 5.75V and a digital interface supply of 3.3V. BLOCK DIAGRAM WOLFSON MICROELECTRONICS plc Production Data, August 2013, Rev 4.7 Copyright 2013 Wolfson Microelectronics plc Production Data WM8255 TABLE OF CONTENTS DESCRIPTION ....................................................................................................... 1 FEATURES ............................................................................................................ 1 APPLICATIONS ..................................................................................................... 1 BLOCK DIAGRAM ................................................................................................ 1 TABLE OF CONTENTS ......................................................................................... 2 PIN CONFIGURATION .......................................................................................... 4 ORDERING INFORMATION .................................................................................. 4 PIN DESCRIPTION ................................................................................................ 5 ABSOLUTE MAXIMUM RATINGS ........................................................................ 6 RECOMMENDED OPERATING CONDITIONS ..................................................... 6 THERMAL PERFORMANCE ................................................................................. 6 ELECTRICAL CHARACTERISTICS ..................................................................... 7 INPUT VIDEO SAMPLING ............................................................................................. 10 OUTPUT DATA TIMING................................................................................................. 10 SERIAL INTERFACE ..................................................................................................... 11 PWM TIMING ................................................................................................................. 12 DEVICE DESCRIPTION ...................................................................................... 13 INTRODUCTION ............................................................................................................ 13 INPUT SAMPLING ......................................................................................................... 13 RESET LEVEL CLAMPING (RLC) ................................................................................. 13 CDS/NON-CDS PROCESSING ..................................................................................... 14 OFFSET ADJUST AND PROGRAMMABLE GAIN ........................................................ 15 ADC INPUT BLACK LEVEL ADJUST ............................................................................ 16 OVERALL SIGNAL FLOW SUMMARY .......................................................................... 16 CALCULATING OUTPUT FOR ANY GIVEN INPUT ...................................................... 16 OUTPUT FORMATS ...................................................................................................... 18 LED CURRENT DRIVE CONTROL ............................................................................... 19 LED CURRENT DRIVE SEQUENCE SYNCHRONISATION AND PROGRESSION ..... 20 LED CURRENT DRIVE INTENSITY CONTROL ............................................................ 21 LED CURRENT DRIVE CURRENT PWM CONTROL .................................................. 25 LED CURRENT DRIVE CURRENT BLANKING PERIOD ............................................. 26 CURRENT ACCURACY AND ABSOLUTE MAXIMUM CURRENT LIMIT ..................... 30 LED CONTROL WORKED EXAMPLE ........................................................................... 32 CONTROL INTERFACE................................................................................................. 34 TIMING REQUIREMENTS ............................................................................................. 34 PROGRAMMABLE VSMP DETECT CIRCUIT ............................................................... 35 REFERENCES ............................................................................................................... 36 POWER SUPPLY ........................................................................................................... 36 POWER MANAGEMENT ............................................................................................... 36 POWER ON SEQUENCE .............................................................................................. 37 OPERATING MODES .................................................................................................... 37 OPERATING MODE TIMING DIAGRAMS ..................................................................... 38 DEVICE REVISION CODES .......................................................................................... 39 DEVICE CONFIGURATION ................................................................................. 40 REGISTER MAP .................................................................................................. 40 EXTENDED PAGE REGISTERS ................................................................................... 41 REGISTER MAP DESCRIPTION ................................................................................... 41 EXTENDED PAGE REGISTER MAP DESCRIPTION ................................................... 45 RECOMMENDED EXTERNAL COMPONENTS .................................................. 46 PD, Rev 4.7, August 2013 w 2