ADC124S051_15 Datasheet, PDF (19/28 Pages) Texas Instruments – 12-Bit A/D Converter

ADC124S051
www.ti.com
SNAS260E – NOVEMBER 2004 – REVISED NOVEMBER 2004
ADC124S051 TRANSFER FUNCTION
The output format of the ADC124S051 is straight binary. Code transitions occur midway between successive
integer LSB values. The LSB width for the ADC124S051 is V_A/4096. The ideal transfer characteristic is shown in
Figure 49. 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_A/8192. Other code transitions occur at steps of one LSB.
111...111
111...110
111...000
|
011...111
1LSB = V_A/4096
000...010
000...001
000...000
0V ^0.5LSB
+V_A - 1.5LSB
ANALOG INPUT
Figure 49. Ideal Transfer Characteristic
TYPICAL APPLICATION CIRCUIT
A typical application of the ADC124S051 is shown in Figure 50. 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 ADC124S051.
Because the reference for the ADC124S051 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 ADC124S051 supply pin. Because of the
ADC124S051's low power requirements, it is also possible to use a precision reference as a power supply to
maximize performance. The four-wire interface is shown connected to a microprocessor or DSP.
1 PF
TANT
LP2950
0.1 PF
1 PF
5V
0.1 PF
IN1
V_A
SCLK
IN2
CS
ADC124S051
IN3
DIN
IN4
DOUT
GND
MICROPROCESSOR
DSP
Figure 50. Typical Application Circuit
Copyright © 2004, Texas Instruments Incorporated
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