DSP applications continue to demand more from less -- more features while consuming less power. Real-time, high-performance processing may seem like the antithesis of low-power design, but it is not. The TMS320LC54x meets these challenges by combining high processing capability with the greatly reduced power consumption that battery-powered and portable applications demand. The future promises even faster, more efficient versions specifically optimized for portable, high-performance end equipment.

Featured this month are two applications documents for those interested in low-power digital signal processor (DSP) design. The audience for these papers are designers of portable, power-sensitive and battery-operated applications such as digital cellular telephones, laptop modems and voice-mail pagers.

"Designing Low-Power Applications with the TMS320LC54x" is an overview of the low-power architectural features and design considerations of the TMS320LC54x DSP family. It highlights the key power-saving features of the 'LC54x design and provides design hints for limiting power consumption.

"Calculation of TMS320C54x Power Dissipation" presents techniques for analyzing system and device conditions to determine operating current levels and power dissipation. From this information, informed decisions can be made regarding power supply requirements and thermal management considerations.

Power supply current requirements for the TMS320LC54x DSPs cannot be expressed simply in terms of operating frequency, supply voltage and output capacitance. A more complete specification, one based on device activity, must be used to determine an accurate power supply current requirement. This application report presents the information necessary to accurately analyze power supply current requirements based on the knowledge of various periods of device activity and their operation of the TMS320LC54x in terms of internal and external activity including operating frequency, supply voltage, operating temperature and output capacitance. The components related to this device activity include CPU activity, peripheral activity and external bus operations. Taking into account, system design may be performed proactively to minimize device and system power dissipation.

The table below is just a small sample of the detailed power characterization data in this application report. This information is critical to designers of low-power, high-performance DSP applications where every device activity translates into a calculation of expected battery life.

TMS320LC54x CPU power dissipation characteristics
Activity	Current (mA per MIPS)	Current at 50 MIPS (mA)
IDLE3	0	0
IDLE2	0.03	1.5
IDLE1	0.12	6
Repeat NOPs	0.3	15
Inline NOPs	0.4	20
Block data transfer in on-chip DARAM using RPT	0.8	40
Repeat MAC with changing data (dual-operand addressing)	1.0	50
Inline MAC with changing data (dual-operand addressing)	1.2	60
Repeat MACD with changing data (single-operand addressing)	0.8	40
Inline MACD with changing data (single-operand addressing)	1.0	50
Repeated double-precision arithmetic instructions with changing data	0.9	45
Inline double-precision arithmetic instructions with changing data	1.1	55
Repeat FIRS with changing data	1.2	60
Inline FIRS with changing data	0.9	45
FIR filter	0.9	45
Full-rate GSM vocoder	1.03	51.5
Complex 256-point FFT	1.07	53.5