AS1545_1 AMSCO [austriamicrosystems AG], AS1545_1 Datasheet - Page 22

• 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
Figure 38. Definition of Fully Differential Input
Pseudo Differential Mode
The AS1545 consists of six pseudo differential pairs. In pseudo differential mode, AIN+ is connected to the signal
source with an amplitude of V
of the part. A dc input is applied to the AIN- pin. The voltage applied to this input provides an offset from ground or a
pseudo ground for the AIN+ input. The benefit of pseudo differential inputs is that they separate the analog input signal
ground from the ADC’s ground allowing dc common-mode voltages to be cancelled.
diagram for pseudo differential mode.
Figure 39. Pseudo Differential Mode Connection Diagram
Figure 40. Definition of Pseudo Differential Input
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AIN- + VREF
VCM
VIN
VIN
VREF p-p
AIN+
AIN-
AIN+
AIN-
RANGE = 0
RANGE = 0
REF
or 2 × V
0 < VCM < VDD
0 < AIN-, AIN+ < VDD
0 < AIN-, AIN+ < VDD
REF
+
-
DC Input Voltage
(depending on the range selected) to make use of the full dynamic range
VREF
±VREF/2
Revision 1.01
t
t
AIN- + 2VREF
VCM
VIN
VIN
VIN-
VIN+
AIN+
AIN+
AIN-
AIN-
AS1545
REFA/
REFB
RANGE = 1
4.7µF
RANGE = 1
Figure 39
0 < VCM < VDD
0 < AIN-, AIN+ < VDD
0 < AIN-, AIN+ < VDD
shows a connection
2VREF
±VREF
t
t
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