Datasheet
ADS8343
10
SBAS183C
www.ti.com
THEORY OF OPERATION
The ADS8343 is a classic Successive Approximation Register
(SAR) A/D converter. The architecture is based on capacitive
redistribution which inherently includes a sample-and-hold func-
tion. The converter is fabricated on a 0.6µm CMOS process.
The basic operation of the ADS8343 is shown in Figure 1.
The device requires an external reference and an external
clock. It operates from a single supply of 2.7V to 5.25V. The
external reference can be any voltage between 500mV and
+V
CC
/2. The value of the reference voltage directly sets the
input range of the converter. The average reference input
current depends on the conversion rate of the ADS8343.
The analog input to the converter is differential and is
provided via a 4-channel multiplexer. The input can be
provided in reference to a voltage on the COM pin (which is
generally V
REF
) or differentially by using two of the four input
channels (CH0-CH3). The particular configuration is select-
able via the digital interface.
ANALOG INPUT
The analog input is bipolar and fully differential. There are
two general methods of driving the analog input of the
ADS8343: single-ended or differential, as shown in Figure 2.
FIGURE 2. Methods of Driving the ADS8343—Single-Ended
or Differential.
FIGURE 1. Basic Operation of the ADS8343.
TYPICAL CHARACTERISTICS: +2.7V (Cont.)
At T
A
= +25°C, +V
CC
= +2.7V, V
REF
= +1.25V, f
SAMPLE
= 100kHz, and f
CLK
= 24 • f
SAMPLE
= 2.4MHz, unless otherwise noted.
Sampling Frequency (kHz)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
SUPPLY CURRENT vs SAMPLING FREQUENCY
10 20 30 40 50 60 70 80 90 100
Supply Current (mA)
f
CLK
= 2.4MHz
V
SS
= 5.0V
V
SS
= 2.7V
Power-Down After Conversion Mode.
External Clock Gated HIGH After Conversion.
+V
CC
CH0
CH1
CH2
CH3
COM
SHDN
V
REF
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
DCLK
CS
DIN
BUSY
DOUT
GND
GND
+V
CC
Chip Select
Serial Data In
Serial Data Out
Serial/Conversion
Clock
1µF
0.1µF
+2.7V to +5V
ADS8343
Single-ended
or differential
analog inputs.
V
REF
+
1µF
to
10µF
ADS8343
ADS8343
Single-Ended Input
CHX
COM
CHX+
CHX–
±V
REF
(1)
Differential Input
NOTE: (1) Relative to common-mode voltage.
Common-Mode
Voltage
Common-Mode
Voltage
(typically V
REF
)
±
V
REF
(1)
2
±
V
REF
(1)
2