ADC104S021 Datasheet, PDF (18/27 Pages) Texas Instruments – 4-Channel, 50 ksps to 200 ksps, 10-Bit A/D Converter

ADC104S021
SNAS278H – FEBRUARY 2005 – REVISED MARCH 2013
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111...111
111...110
111...000
|
011...111
1LSB = VA/1024
000...010
000...001
000...000
0V ^0.5LSB
+VA - 1.5LSB
ANALOG INPUT
Figure 48. Ideal Transfer Characteristic
TYPICAL APPLICATION CIRCUIT
A typical application of the ADC104S021/ADC104S021Q is shown in Figure 49. Power is provided in this
example by the Texas Instruments 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
ADC104S021/ADC104S021Q.
Because the reference for the ADC104S021/ADC104S021Q 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 ADC104S021/ADC104S021Q supply
pin. Because of the ADC104S021/ADC104S021Q'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 also 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 _ADC104S021 ^CS
IN3
DIN
IN4
DOUT
GND
MICROPROCESSOR
DSP
Figure 49. Typical Application Circuit
ANALOG INPUTS
An equivalent circuit for one of the ADC104S021/ADC104S021Q's input channels is shown in Figure 50. Diodes
D1 and D2 provide ESD protection for the analog inputs. At no time should any input go beyond (V_A + 300 mV)
or (GND − 300 mV), as these ESD diodes will begin conducting, which could result in erratic operation. For this
reason, these ESD diodes should NOT be used to clamp the input signal.
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