Datasheet

MICROPROCESSOR
DSP
SCLK
CS
SDATA
GND
V
A
ADC081S051
LP2950
5V
1 PF
0.1 PF 0.1 PF1 PF
V
IN
000...001
000...010
0V
011...111
111...000
000...000
111...111
111...110
ADC CODE
ANALOG INPUT
1 LSB = V
A
/256
1 LSB
+V
A
-1 LSB
||
|
ADC081S051
www.ti.com SNAS309E –APRIL 2005–REVISED MARCH 2013
ADC081S051 TRANSFER FUNCTION
The output format of the ADC is straight binary. Code transitions occur midway between successive integer LSB
values. The LSB width for the ADC is V
A
/256. The ideal transfer characteristic is shown in Figure 20. The
transition from an output code of 0000 0000 to a code of 0000 0001 is at 1/2 LSB, or a voltage of V
A
/512. Other
code transitions occur at steps of one LSB.
Figure 20. Ideal Transfer Characteristic
TYPICAL APPLICATION CIRCUIT
A typical application of the ADC is shown in Figure 21. Power is provided in this example by the LP2950 low-
dropout voltage regulator, available in a variety of fixed and adjustable output voltages. The power supply pin is
bypassed with a capacitor network located close to the ADC. Because the reference for the ADC is the supply
voltage, any noise on the supply will degrade device noise performance. To keep noise off the supply, use a
dedicated linear regulator for this device, or provide sufficient decoupling from other circuitry to keep noise off the
ADC supply pin. Because of the ADC's low power requirements, it is also possible to use a precision reference
as a power supply to maximize performance. The three-wire interface is shown connected to a microprocessor or
DSP.
Figure 21. Typical Application Circuit
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