adc1220 austriamicrosystems, adc1220 Datasheet - Page 8

• Manufacturer Part Number: adc1220
• Description: Cmos 12-bit Pipelined A/d Converter
• Manufacturer: austriamicrosystems

Datasheet : ADC1220 – C35
POWER SUPPLIES
The converter requires a single +3.3 V power supply. The supplies for analog and digital are separated. For maximum noise immunity it is
recommended to wire them on chip to separated pins, especially when the block is embedded in a large digital circuit. The supplies may then be
connected together on PC-board level.
The proper use of blocking capacitors in the application is important!
REFERENCE VOLTAGES
If ONREF is set to high the converter needs an external bandgap reference VBG that defines the dynamic range of the input signal as described in
the technical data section. If ONREF is set to low the external voltage references VREFP and VREFN define the dynamic range of the input signal.
The proper use of blocking capacitors in the application is important!
SYSTEM REQUIREMENTS
The ADC is sensitive to ground noise. So all parts of the whole system except the ADC should be quiet during the conversions. To minimize
ground noise coming from digital output pads the connection of a series resistor should be used to limit the switching current. In the test circuit a
series resistor of 1 kΩ is used for the digital output bus.
CONVERSION MODE
Fully Differential Mode
It is recommended to use the ADC1220 as a Fully Differential Converter. Both inputs VINP and VINN should be balanced around VCM.
CODE TABLES
The digital representation of the data bus in both conversion modes is described in the following table.
Offset Binary
Revision B, 08.09.02
VREF
=
VREFP
−
VREFN
Output Code
1111 1111 1111
1111 1111 1110
…
1000 0000 0001
1000 0000 0000
0111 1111 1111
0111 1111 1110
…
0000 0000 0001
0000 0000 0000
,
1
LSB
=
VREFP
4096
−
VREFN
Input Voltage: VIN-VINB
2047 LSB … VREF
2046 LSB … 2047 LSB
…
1 LSB … 2 LSB
0 … 1 LSB
–1 LSB … 0
–2 LSB … –1 LSB
…
–2047 LSB … –2046 LSB
–VREF … –2047 LSB
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