Low Power Baseband Modem LSI

Mitsubishi Electric Corporation has developed a low power baseband modem LSI for W-CDMA mobile phones. The LSI was installed in D900i, achieving approx. 170/90 minutes of continuous talk time for voice/video phones, and approx. 550/420 hours of continuous standby time in stationary/moving states respectively. The architecture of this LSI is similar to that of the baseband modem LSI chipset used for D2101V, which was optimized for lowering power consumption. To realize this LSI, 0.15 um low leak semiconductor process technology was applied to integrate an AFE (Analog Front End), a CPU, two DSPs and a hardware accelerator on a 10.6mm-square silicon chip. Then the chip was packed into a 15mm-square, 513-ball FBGA, and along with an external memory package (stacking 32M-bit Flash ROM and 32M-bit PSRAM), the LSI enables baseband modem processing for W-CDMA mobile phones. To extend talk time, talk current was reduced by means of (1) minimizing the hardware (to fit into one chip) by optimizing the algorithm and the required memory size for each function; (2) shortening the circuit operation time by thoroughly applying a clock gating technique to each circuit; and (3) decreasing the internal power voltage of the LSI (from 1.8V to 1.5V) by applying optimized semiconductor process. As a result, the operating current for baseband modem processing, which previously accounted for 35%-40% (200mA) of total talk current was reduced by 85%. The standby time was also extended with reduced standby current by means of (4) shortening the processing time by modifying the software for standby processing in communication control, which decreased 90% of the operating current that previously accounted for over 60%(7mA) of the total standby time; (5) reducing the leak current (to half) by partly turning on/off the internal power of the LSI; etc.