Forums

Low-power, Low-cost DSP chip

Started by Edward E. Hopkins October 18, 2003
Ok I am hunting for a low-power AND low-cost DSP.  I have searched all major
manufacturers (Zilog, Intel, TI, AD, and Mot) and have not yet found a
suitable DSP to meet a stringent cost and power spec imposed on me.

I've checked the TI 320 C6000, 5000, and 2000 series but they are just too
expensive and consume too much power.  The AD (blackfin, SHARC) chips appear
to be no better on power consumption.

What would you guys say is going to be the most accurate (preferrably 32-bit
floating point) fastest DSP on that market that can manage < 10 mA average
current load and cost <$20 per KU ?  Cost of dev board and compiler is also
an issue.  Must have a total dev cost of < $1500 total.  It's an engineering
class project so we have pretty low budgets.

Ed


"Edward E. Hopkins" wrote:
> What would you guys say is going to be the most accurate (preferrably 32-bit > floating point) fastest DSP on that market that can manage < 10 mA average > current load and cost <$20 per KU ? Cost of dev board and compiler is also > an issue. Must have a total dev cost of < $1500 total. It's an engineering > class project so we have pretty low budgets.
I have a project with similar specifications. An important question that needs to be answered is what rate of computation do you actually require? Many DSPs have power management features that allow large parts of the chip to be idled or even powered down when not busy, and this can have a huge effect on the overall power consumption. Another alternative is to simply run the chip at a slower clock rate all the time, although this doesn't have the dramatic effect it once did. If you need floating point, have you considered the ADSP-21065L? The Blackfin series is fast and has many power-management features, but only does integer arithmetic in hardware; floating-point must be emulated. Many RISC chips intended for portable operation (e.g., ARM) can do DSP type tasks quite efficiently, and might meet your needs. Free or low-cost development tools are often available as well. -- Dave Tweed
Hi Edward

If you really need to be <10mA you will need to underclock the DSP.  If
you stick to the internal currents and ignore leakage, you will find
current to be proportional to clocking frequency.  That is, if you clock
a 100Mhz device at 1Mhz the current drops by a 100:1 ratio.

Another small problem here is that if I had a 10mA budget at 18V, then I
could convert this to 100mA @1.8V which is what the core voltage needs
to be in a lot of new devices.

The next things you need to start considering will be
   leakage which is becoming rather significant these days
   external memory (aint free and consumes power)
   analog codec, op-amps etc...

If you have a look at the TMS320VC33 DSK you will find that at the board
level it consumes ~100-125mA @5V.  However, do keep in mind that this
board is made to be low cost, simple and low noise, so no switching
supplies are used.  I have mentioned on several occasions that using a
linear regulator for the the 1.8V core is far from being power
efficient, but that this was not the goal.  You may also find that with
1.1Mb of on-chip memory you dont even need external memory, and this
would be another waste of power and board space and cost.  The board 
also does come with the compiler and the DSK tool sources are provided 
free of charge to TMS320 users.

Best regards,
Keith Larson
----------------------------------------
Edward E. Hopkins wrote:

  Ok I am hunting for a low-power AND low-cost DSP.  I have searched all
major manufacturers (Zilog, Intel, TI, AD, and Mot) and have not yet
found a suitable DSP to meet a stringent cost and power spec imposed on me.

I've checked the TI 320 C6000, 5000, and 2000 series but they are just
too expensive and consume too much power.  The AD (blackfin, SHARC)
chips appear to be no better on power consumption.

What would you guys say is going to be the most accurate (preferrably
32-bit floating point) fastest DSP on that market that can manage < 10
mA average current load and cost <$20 per KU ?  Cost of dev board and
compiler is also an issue.  Must have a total dev cost of < $1500 total.
  It's an engineering class project so we have pretty low budgets.

Ed

+------------------------------------------+
|Keith Larson                              |
|Member Group Technical Staff              |
|Texas Instruments Incorporated            |
|                                          |
| 281-274-3288                             |
| k-larson2@ti.com                         |
|------------------------------------------+
|     TMS320C3x/C4x/VC33 Applications      |
|                                          |
| $150 TMS320VC33 DSK's ARE AVAILABLE NOW  |
|                                          |
|               TMS320VC33                 |
|    The lowest cost and lowest power      |
|    floating point DSP on the planet!     |
|              500uw/Mflop                 |
+------------------------------------------+