XRD8799 Datasheet, PDF (10/23 Pages) Exar Corporation – LOW POWER, 2 MSPS, 10-BIT, A/D CONVERTER WITH 8-CHANNEL MUX

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XRD8799
LOW POWER, 2 MSPS, 10-BIT, A/D CONVERTER WITH 8-CHANNEL MUX
REV. 1.00
FIGURE 5. XRD8799 COMPARATORS
External
Update
References
Clock
Internal
AIN Sample
Window
Ladder Sample
Window (MSB Bank)
Ladder Compare
(LSB Bank)
External
DATA
Settle by Clock Update Time
Short Cycle Sample will be discarded
t_S
Reference Stable Time - For Sample A _IN1
Hold Reference Value Past
Clock Change for t_AP Time
Reference Stable Time - For Sample A _IN2
A _INX0
Sample A IN1
ΦB
ΦS
Sample A _IN1
Sample Ladder
for A _IN1
AINX1
ΦB ^{Not Used} ΦS
A_INX1
Sample Ladder
for A_INX1
Sample A IN2
ΦB
ΦS
Sample A _IN2
Sample Ladder
for _AIN2
Sample Ladder
for A _INX2
Compare Ladder
V/S A _INX0
Compare Ladder
V/S A _IN1
Compare Ladder
V/S A _INX1
Compare Ladder
V/S A _IN2
DATA A _IN0
DATA A _INX0
Not Used
DATA A _IN1
DATA A _INX1
Not Used
1.1 ACCURACY OF CONVERSION: DNL AND INL
The transfer function for an ideal A/D converter is
shown in Figure 6.
FIGURE 6. IDEAL A/D TRANSFER FUNCTION
DIGITAL
CODES
1 LSB
002
001
000
LSB
V_REF(-)
V001
V002
OFW=0
OFW=1
3FF
3FE
3FD
V_3FE
V_3FF
V
V_0FW = V_REF(+)
The overflow transition (VOFW) takes place at:
V_IN = VOFW = V_REF(+)
The first and the last transitions for the data bits take
place at:
V_IN = V001 = V_REF(-) + 1.0 * LSB
V_IN = V3FF = V_REF(-) - 1.0 * LSB
V_REF = V_REF(+) - V_REF(-)
LSB = V_REF / 1024 = (V_3FF - V001) / 1022
NOTE: 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 V_REF/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 V_REF =
4.608 V then 1 LSB = 4.5 mV and every code width is
within 2.25 and 6.75 mV.
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