Datasheet

IN1
IN2
MICROPROCESSOR
DSP
SCLK
CS
DIN
DOUT
GND
V
A
LP2950
5V
1 PF
TANT
0.1 PF 0.1 PF1 PF
IN3
IN4
ADC104S021
| |
|
0V
+V
A
- 1.5LSB
0.5LSB
ANALOG INPUT
1LSB = V
A
/1024
ADC CODE
111...111
111...110
111...000
011...111
000...010
000...001
000...000
ADC104S021
SNAS278H –FEBRUARY 2005–REVISED MARCH 2013 www.ti.com
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.
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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