Built-in duty cycle corrector using coded phase blending scheme for DDR/DDR2 synchronous DRAM application

This paper describes DLL (delay locked loop) with built-in DCC (duty cycle correction) capability using a newly proposed coded phase blending scheme. The proposed scheme dramatically improves the DCC range and also enhances the total DLL performance. The DLL has been designed and fabricated within 1G-bit DDR (double data rate) synchronous DRAM using 0.11 mum process and the measurement data show that it has unlimited DCC range, faster turn-on speed and smaller jitter compared with our previous work [1].