AS1545_1 AMSCO [austriamicrosystems AG], AS1545_1 Datasheet - Page 21

• Manufacturer Part Number: AS1545_1
• Description: Dual, 12-Bit, 1MSPS, SAR ADC
• Manufacturer: AMSCO [austriamicrosystems AG]

AS1545
Datasheet - D e t a i l e d D e s c r i p t i o n
Single-Ended Mode
The AS1545 consists of 12 single-ended analog input channels with range that can be programmed to be either 0 to
V
Note: In applications where the signal source has high impedance, it is recommended to buffer the analog input
If the sampling analog input is bipolar, the internal reference of the ADC can be used to externally bias up this signal to
make it correctly formatted for the ADC.
ended mode.
Figure 36. Single-Ended Mode Connection Diagram
Figure 37. Definition of Single-Ended Input
Fully Differential Mode
The AS1545 consists of six differential analog input pairs.
AS1545. The amplitude of the differential signal is the difference between the signals applied to the AIN+ and AIN- pins
in each differential pair (AIN+ - AIN-). These pins should be simultaneously driven by two signals each of amplitude
V
of the differential signal is ±V
The common mode is the average of the two signals and is therefore the voltage on which the two inputs are centered.
Althought fully differential operation with phase between inputs of 180° is recommanded, non true differential signals
can also be applied.
Note: It is important to note that the absolute voltage of the analog inputs goes from AGND to V
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REF
REF
/2 (or V
or 0 to 2 × V
before applying it to the ADC.
VIN
REF
, depending on the range required) that are 180º out of phase. If RANGE = 1 is selected the amplitude
+1.25V
-1.25V
REF
0V
.
RANGE = 0
V
IN
REF
regardless of the common mode (CM).
3R
R
R
Figure 36
0 < AIN < VDD
+
-
(V
VREF
shows the connecting diagram when operating the ADC in single-
IN
R
+ + V
Revision 1.01
t
IN
Figure 38
-)/2
10Ω
VIN
defines the fully differential analog input of the
10nF
+
-
+2.5V
0V
AIN0 to BIN5
RANGE = 1
REFA/
REFB
4.7µF
0 < AIN < VDD
DD
.
2VREF
t
21 - 34
(EQ 1)