James, it sounds like you've looked at the most popular chips. I've used
the ML2036 as part of a PIC-based DAQ system. If you don't mind a 1Hz
resolution, the ML2036 seems ideal. All you need is a crystal (literally, no
capacitors). It requires +/- 5V and has a 3-wire SPI-style interface. You
clock-in 16 Bits, LSB first, and set a Latch Enable line to set the
frequency from 1 to 50KHz (I tested it to 65,535KHz). By using a 8.388608MHz
crystal (Digi-Key PN: SE3415 / Epson CA-301 family), you get a direct
one-to-one program data to frequency setting with a 1Hz resolution. The chip
provides Osc/2 and Osc/8 outputs which may be of use if you want to clock a
PIC at 4.194304MHz.

   There is a voltage reference input. Tying this to +5V gives a maximum
output swing of +/- 2.5Vp-p. You can reduce this via an external reference.
Harmonic distortion is -45db max. The device comes in a 14-pin DIP or 16-pin
SOIC package. For more info:

      http://www.microlinear.com/

   - Tom

At 12:42 PM 2/22/01 -0000, James Hillman wrote:
>I am using a PIC to make a frequency generator 0 to 50,000 Hz with 0.01%
>resolution. I have searched the PICLIST archives and the most suitable IC I
>have come across to do the frequency generation is the ML2036 from Fairchild
>semiconductor. Can anyone suggest anything else ?
>
>Maxim MAX038, Harris HSP45102, Motorola MC145162,Analog Devices AD9850 are
>too expensive and designed for RF so aren't really suitable.
>I have considered using a Direct Digital Synthesis (DDS) algorithm, but
>there is too much else going on in the processor to do this.
>
>Thanks in advance,
>
>James


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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