MPC5673K datasheet(80/147 Pages) NXP

80 / 147 page

MPC5675K Microcontroller Data Sheet, Rev. 8.1

Electrical characteristics

NXP Semiconductors

3.14

ADC electrical characteristics

The MPC5675K provides a 12-bit Successive Approximation Register (SAR) Analog-to-Digital Converter.

Figure 8. ADC characteristics and error definitions

3.14.1

Input impedance and ADC accuracy

To preserve the accuracy of the A/D converter, it is necessary that analog input pins have low AC impedance. Placing a capacitor

with good high frequency characteristics at the input pin of the device can be effective: the capacitor should be as large as

possible, ideally infinite. This capacitor contributes to attenuating the noise present on the input pin; further, it sources charge

during the sampling phase, when the analog signal source is a high-impedance source.

A real filter can typically be obtained by using a series resistance with a capacitor on the input pin (simple RC filter). The RC

filtering may be limited according to the value of source impedance of the transducer or circuit supplying the analog signal to

be measured. The filter at the input pins must be designed taking into account the dynamic characteristics of the input signal

(bandwidth) and the equivalent input impedance of the ADC itself.

IRCTRIM

CC Internal RC oscillator trimming step

TA = 25 °C

—

1.6

—

1 PTF = Post Trimming Frequency: The frequency of the output clock after trimming at typical supply voltage and

temperature.

Table 23. RC oscillator electrical characteristics (continued)

No.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

(2)

( 1)

(3)

(4)

(5)

Offset Error OSE

Gain Error GE

1 LSB (ideal)

Vin(A) (LSBideal)

(1) Example of an actual transfer curve

(2) The ideal transfer curve

(3) Differential non-linearity error (DNL)

(4) Integral non-linearity error (INL)

(5) Center of a step of the actual transfer

curve

code out

4095

4094

4093

4092

4091

4090

4089 40904091 40924093 4094 4095

1 LSB ideal =(VrefH-VrefL)/ 4096 =

3.3 V/ 4096 = 0.806 mV

Total Unadjusted Error

TUE =

±6 LSB = ±4.84 mV

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