Datasheet

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APPLICATION INFORMATION
MICROCONTROLLER INTERFACING
ADS8405 to 8-Bit Microcontroller Interface
CS
RD
CONVST
BUSY
BDGND
+VBD
DB[15:8]
Micro
Controller
RD
GPIO
INT
10 µF
0.1 µF
Analog 5 V
0.1 µF
Digital 3 V
Ext Ref Input
Analog Input
+VA
REFM
AGND
+IN
−IN
ADS8405
0.1 µF
REFIN
1 µF
AGND
BDGND
GPIO BYTE
P[7:0]
GPIO
+VA
REFOUT
REFIN
REFM
AGND
0.1 µF
1 µF
0.1 µF
10 µF
Analog 5 V
ADS8405
AGND
AGND
PRINCIPLES OF OPERATION
ADS8405
SLAS427 – DECEMBER 2004
Figure 31 shows a parallel interface between the ADS8405 and a typical microcontroller using the 8-bit data bus.
The BUSY signal is used as a falling-edge interrupt to the microcontroller.
Figure 31. ADS8405 Application Circuitry (Using an External Reference)
Figure 32. Using the Internal Reference
The ADS8405 is a high-speed successive approximation register (SAR) analog-to-digital converter (ADC). The
architecture is based on charge redistribution, which inherently includes a sample/hold function. See Figure 31
for the application circuit for the ADS8405.
The conversion clock is generated internally. The conversion time of 650 ns is capable of sustaining a 1.25-MHz
throughput.
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