AS1543/44
Data Sheet - Application Information
9 Application Information
Figure 35 shows a typical connection diagram for the AS1543/44. In this configuration, pin AGND, GND and DGND
connected to the analog ground plane of the system. In Figure 35, REFIN is connected to a decoupled 2.5V reference
source, to provide an analog input range of 0 to 2.5V (if RANGE (page 14) is 1 and bit SE/FDN (page 14) = 1) or 0 to
5V (if bit RANGE is 0 and bit SE/FDN = 1). In Figure 35 the AS1543/44 is connected to a VDD of 5V, however the serial
interface is connected to a 3V microprocessor.
Pin VDRIVE is connected to the same 3V supply of the microprocessor to allow a 3V logic interface. The conversion
result is output in a 16-bit word. This 16-bit data stream consists of four address bits indicating which channel the con-
version result corresponds to, followed by the 12 bits of conversion data.
Note: For applications where power consumption is of concern, the power-down modes should be used between
conversions or bursts of several conversions to improve power performance (see Power Modes on page 22).
Figure 35. Typical Application
5V
VDD
SCLK
DOUT
DIN
0.1µF
10µF
GND
DSP/µP
0V to
VREFIN
AS1543/44
VIN0:3/7
CSN
2.5V
REFIN
AGND
VDRIVE
0.1µF
10µF
4.7µF
3V
DGND
Note: For the circuit shown in Figure 35, unused input channels should be connected to ground. For optimum perfor-
mance decouple all analog input channels and the reference input voltage to the ground of AGND.
Initialisation
When power is first applied to the AS1543/44 interal power-on reset circuitry sets the device for Auto Shutdown (PM1
= 0, PM0 = X) on page 23.
Note: The device requires 10µs after the power supplies stabilize; no conversions should be initiated during this time.
The digital output at pin DOUT will be set to tri-state after internal power-on reset.
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