On 08/09/2012 01:02 PM, Matt Dexter wrote:
something seems strange. isn't the input range of the ADC IC :
Vin FSR pin14 low .590 to .730 Vpp
Vin FSR pin15 high .800 to .940 Vpp
page 11 of 46 of http://www.ti.com/lit/gpn/adc08d1520
I see +/-50 mV but thats for the common mode input.
On Thu, 9 Aug 2012, Tom Kuiper wrote:
The KatADC is based on the Texas Instruments ADC08D1520. It is an
8-bit (255-level) ADC operating between +/- 50 mV (0.392 mV/step).
The KatADC has a 20 dB amplifier (factor of 10 voltage gain). So
this gives it an input range of +/- 5 mV, or 0.0392 mV/step (39.2
uV/step). In the KAT RFI 16K spectrometer code I see a count to mV
scale factor of 3.93. I'm missing something. Can anyone set me
straight?
Thank you, Matt and Dana for the tips. I had not drilled down to p. 11
(or rather, p. 10 on the sheet I have). If we take the advisable
operating range as +/- 500 mV we arrive at 3.92 mV/step. That seems
reasonable. 0.5 V is 7 dBm. The amplifier 1dB compression point is 20
dBm output so this seems like a good operating range for the amp.
Thanks again,
Tom
