ADC121C021CIMKX NSC [National Semiconductor], ADC121C021CIMKX Datasheet - Page 15

• Manufacturer Part Number: ADC121C021CIMKX
• Description: I2C-Compatible, 12-Bit Analog-to-Digital Converter (ADC) with Alert Function
• Manufacturer: NSC [National Semiconductor]

1.3 ADC TRANSFER FUNCTION
The output format of the ADC121C021 is straight binary.
Code transitions occur midway between successive integer
LSB values. The LSB width for the ADC121C021 is V
The ideal transfer characteristic is shown in Figure 5. The
transition from an output code of 0000 0000 0000 to a code
of 0000 0000 0001 is at 1/2 LSB, or a voltage of V
Other code transitions occur at intervals of 1 LSB.
FIGURE 5. Ideal Transfer Characteristic
A
A
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1.4 REFERENCE VOLTAGE
The ADC121C021 uses the supply (V
With that said, V
to-digital conversion will only be as precise as the reference
(V
is also recommended that the reference be driven by a volt-
age source with low output impedance.
The Applications section provides recommended ways to
drive the reference (V
details.
1.5 POWER-ON RESET
The power-on reset (POR) state is the point at which the sup-
ply voltage rises above the power-on reset threshold, gener-
ating an internal reset. Each of the registers contains a
defined value upon POR and this data remains there until any
of the following occurs:
•
•
•
When resetting the device, it is crutial that the V
lowered to a maximum of 200mV before the supply is raised
again to power-up the device. Dropping the supply to within
200mV of GND during a reset will ensure the ADC performs
as specified.
A
The first conversion is completed, causing the Conversion
Result Register and various status registers to be updated
internally.
The master writes a different data word to any of the
writeable registers.
The ADC is powered down.
). Therefore, the reference (V
A
must be treated as a reference. The analog-
A
) appropriately. Refer to Section 2.1 for
A
) should be free of noise. It
A
) as the reference.
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A
supply be