MP8798AN 查看數據表（PDF） - Exar Corporation

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MP8798AN

CMOS Very Low Power, 1 MSPS 10-Bit Analog-to-Digital Converter with 4-Channel Mux

Exar Corporation 

MP8798

Accuracy of Conversion: DNL and INL

The transfer function for an ideal A/D converter is shown in

Figure 4.

DIGITAL

CODES

0.5 ∗ LSB

0.5 ∗ LSB

OFW = 0 OFW = 1

1 LSB

3FF

3FE

002 3FD

001

000 LSB

V

VREF(–) V001 V002

V3FE V3FF V0FW VREF(+)

Figure 4. Ideal A/D Transfer Function

The overflow transition (VOFW) takes place at:

VIN = VOFW = VREF(+) – 0.5 ∗ LSB

The first and the last transitions for the data bits take place at:

VIN = V001 = VREF(–) + 0.5 ∗ LSB

VIN = V3FF = VREF(+) – 1.5 ∗ LSB

LSB = VREF / 1024 = (V3FF – V001) / 1022

Note that the overflow transition is a flag and has no impact on

the data bits.

In a “real” converter the code-to-code transitions don’t fall

exactly every VREF/1024 volts.

A positive DNL (Differential Non-Linearity) error means that

the real width of a particular code is larger than 1 LSB. This error

is measured in fractions of LSBs.

A Max DNL specification guarantees that ALL code widths

(DNL errors) are within the stated value. A specification of Max

DNL = + 0.5 LSB means that all code widths are within 0.5 and

1.5 LSB. If VREF = 4.608 V then 1 LSB = 4.5 mV and every code

width is within 2.25 and 6.75 mV.

Analog

Input

DNL LSB

Output

Codes

(N+1) Code Width = V(N+1) – V(N)

LSB = [ VREF(+) – VREF(–) ] / 1024

DNL(N) = [ V(N+1) – V(N) ] – LSB

V(N+1)

V(N)

N+1

N

N–1

Figure 5. DNL Measurement

On Production Tester

The formulas for Differential Non-linearity (DNL), Integral

Non-Linearity (INL) and zero and full scale errors (EZS, EFS) are:

DNL (001) = V002 – V001 – LSB

:::

DNL (3FE) = V3FF – V3FE – LSB

EFS (full scale error) = V3FF – [VREF(+) –1.5 ∗ LSB]

EZS (zero scale error) = V001 – [VREF(–) + 0.5 ∗ LSB]

DIGITAL

CODES

0.5 ∗ LSB

1.5 ∗ LSB

EZS

002

001

000

EFS

3FF

3FE

VREF(–) V001 V002

V3FE

V

V3FF VREF(+)

Figure 6. Real A/D Transfer Curve

Figure 6. shows the zero scale and full scale error terms.

Rev. 3.00

7

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