AFS090 datasheet(120/334 Pages) MICROSEMI

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Device Architecture

2- 10 4

R e v isio n 2

INL – Integral Non-Linearity

INL is the deviation of an actual transfer function from a straight line. After nullifying offset and gain

errors, the straight line is either a best-fit straight line or a line drawn between the end points of the

transfer function (Figure 2-83).

LSB – Least Significant Bit

In a binary number, the LSB is the least weighted bit in the group. Typically, the LSB is the furthest right

bit. For an ADC, the weight of an LSB equals the full-scale voltage range of the converter divided by 2N,

where N is the converter’s resolution.

EQ 13 shows the calculation for a 10-bit ADC with a unipolar full-scale voltage of 2.56 V:

1 LSB = (2.56 V / 210) = 2.5 mV

EQ 13

No Missing Codes

An ADC has no missing codes if it produces all possible digital codes in response to a ramp signal

applied to the analog input.

Offset Error

Offset error indicates how well the actual transfer function matches the ideal transfer function at a single

point. For an ideal ADC, the first transition occurs at 0.5 LSB above zero. The offset voltage is measured

by applying an analog input such that the ADC outputs all zeroes and increases until the first transition

occurs (Figure 2-84 on page 2-105).

Figure 2-83 • Integral Non-Linearity (INL)

Input Voltage to Prescaler

INL = +0.5 LSB

INL = +1 LSB

Ideal Output

Actual Output

AFS090 Datasheet(PDF) 120 Page - Microsemi Corporation