GENERAL DESCRIPTION CS6721 integrates three main functions in a single chip providing optimal solutions for various fiber module applications. The functional blocks include a 2.5G postamplifier, a 1.25G burst or continuous mode LD driver, and an 8-bit MCU for configuring and controlling the module functions. The post-amplifier receives AC coupled differential signal from pre-amplifier and performs the quantization amplifications. There are total four amplification stages excluding the output stage. The offset cancellation is built-in on chip. The LOS status is also configurable as a set peak level detection by the post-amplifier or combined with ADC detection on peak level. The LD driver performs the transmit function that receives the PECL differential signal TXINP/TXINN and convert to drive LD output driver. The LD driver is also controlled by burst-enable signal BENN/BENP. The polarity of control can be configured. The laser driver includes differential modulation outputs and DC bias control output. The setting of output power level is controlled through automatic power control loop and is configurable by MCU. The output can be connected to Laser diode either by AC or DC coupled. The transmit path can be enabled or disabled by TXEN signal. The on-chip MCU is the flexibility and versatility of controlling and configurations of fiber module design. Almost all configurations and parameters of the PA and LD driver parameters and can be controlled by MCU through software. The 12-bit ADC associated with MCU can be used to acquire various internal and external analog signals such on-chip temperature sensor and reference voltages. The MCU has 2K boot ROM and 2K SRAM for program storage which can meet the need of application of SFP/PON, Also the boot ROM is responsible for uploads the user program from external serial EEPROM(with capacity of 2k 4k 8k), The I2C slave interface also serves as ISP/IAP interface as well as SFP/SFF DMI function. CS6721 integrates essential building blocks for Fiber module design. The integration of MCU allows precision control to tailor various module applications and facilitates configuration and automatic calibration in the manufacturing process. Using CS6721, the module can achieve low cost and high performance and can be applied in FTTH, BPON, GEPON, and GPON. APPLICATIONS ¨ SONET/SDH, FTTH, GEPON, GPON FEATURES Post Amplifier ¨ 1.25GBPS – 2.5GBPS ¨ -3dB bandwidth 50KHz – 2GHz ¨ 2mV sensitivity ¨ On-chip offset cancellation ¨ Programmable signal detect level and hysteresis ¨ Programmable LOS function and Power detection SD control Peak/ADC control External Monitor/ADC control ¨ Programmable power down ¨ CML output LD Driver ¨ Programmable bias current (up to 100mA) ¨ Programmable modulation current (up to 80mA) ¨ Digital automatic power control loop Fast acquisition of laser power < 3 bursts Programmable loop time constant Update only at burst-off state Loop monitoring by MCU ¨ Rise/Fall time < 200psec ¨ Burst or continuous mode compatible ¨ Programmable polarity and FAIL status DCBIAS fail MPD fail APC fail ¨ Programmable power down and TX enable/disable function ¨ Laser power monitor and burst-on monitor Micro Controller (MCU) ¨ RISC CPU – 12.5MHz 2K Program ROM for Boot 2K Program SRAM for user program Watchdog timer Low voltage reset ¨ I2C master for EEPROM program upload and data storage ¨ I2C slave for host ISP/IAP and DMI Two level password protection for A0/A2 access Support software TX_DISABLE Burst Counter A0/A2 or B0/B2 configurable ¨ 8-Channel 12-bit ADC ¨ 10-bit R2R DAC ¨ On-chip temperature sensor General ¨ Low power consumption (300mW) ¨ Single 3.3V supply with on-chip regulator ¨ Extended temperature range -40oC ~ +85oC ¨ RoHS compliance package |