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ACHIEVING HIGH ACCURACY AND 13-BIT RESOLUTION WITH ST7LITE2 ADC

3.3 HARDWARE FILTERING

Figure 6 shows the hardware setup used in the reference application.

To minimize the effect of external noise (on the supply and input signal), shielded core wire is

used with capacitors C1 = C2 = 0.01µF, C3 = 1000µF, C4 =100µF. These capacitors should

be placed very close to the device input pins with short leads.

The values of these capacitors may vary from application to application, as they depend on

noise behavior and supply type.

Care should be taken regarding the shield; all grounds and shields in the application must be

connected in star format to earth. In addition to this you can use a precision voltage reference

to reduce the effect of supply noise on conversion accuracy. This can have the disadvantage

of extra cost.

Figure 6 Hardware Setup

4 REFERENCE APPLICATION

The resolution of the ADC is 13-bit when the amplifier is ON, so even a small amount of noise

can create an error at output. This noise could be from the supply or the signal. To filter this out

and to obtain correct converted data it is suggested to use different software and hardware

techniques depending on your application requirements, like hardware filtering/shielding/soft-

ware averaging/histogram etc.

However, taking into account this fact, the reference application has been provided showing

the implementation of software averaging, offset compensation and hardware filtering (refer to

Section 3.3 for hardware filtering).

Supply

Ground

Analog Input

C2

C3

C4

+

+

_

_

C1, C2 = Ceramic Capacitors

C3, C4 = Electrolytic Capacitors

ST7LITE2

AIN0/PBO

Application

Board

C1