Datasheet

FFT
-160
-140
-120
-100
-80
-60
-40
-20
0
20
0 100 200 300 400 500
f-Frequency-kHz
Amplitude-dB
10kHzInput,
+VA =5V,
f =1MSPS,
V =5V
s
ref
FFT
-160
-140
-120
-100
-80
-60
-40
-20
0
0 100 200 300 400 500
f-Frequency-kHz
Amplitude-dB
100kHzInput,
+VA =5V,
f =1MSPS,
V =5V
s
ref
THEORY OF OPERATION
ANALOG INPUT
ADS8329
ADS8330
SLAS516C – DECEMBER 2006 – REVISED JULY 2009 ................................................................................................................................................... www.ti.com
TYPICAL CHARACTERISTICS (continued)
Figure 49.
Figure 50.
The ADS8329/30 is a high-speed, low power, successive approximation register (SAR) analog-to-digital
converter (ADC) that uses an external reference. The architecture is based on charge redistribution, which
inherently includes a sample/hold function.
The ADS8329/30 has an internal clock that is used to run the conversion but can also be programmed to run the
conversion based on the external serial clock, SCLK.
The ADS8329 has one analog input. The analog input is provided to two input pins: +IN and – IN. When a
conversion is initiated, the differential input on these pins is sampled on the internal capacitor array. While a
conversion is in progress, both +IN and – IN inputs are disconnected from any internal function.
The ADS8330 has two inputs. Both inputs share the same common pin, COM. The negative input is the same as
the – IN pin for the ADS8329. The ADS8330 can be programmed to select a channel manually or can be
programmed into the auto channel select mode to sweep between channel 0 and 1 automatically.
When the converter enters hold mode, the voltage difference between the +IN and – IN inputs is captured on the
internal capacitor array. The voltage on the – IN input is limited between AGND – 0.2 V and AGND + 0.2 V,
allowing the input to reject small signals which are common to both the +IN and – IN inputs. The +IN input has a
range of – 0.2 V to V
REF
+ 0.2 V. The input span [+IN – ( – IN)] is limited to 0 V to V
REF
.
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