7106_15 Datasheet, PDF (8/18 Pages) Unisonic Technologies – CONVERTERS

7106
„ DETAILED DESCRIPTION(Cont.)
CMOS IC
DIFFERENTIAL REFERENCE
The reference voltage can be generated anywhere within the power supply voltage of the converter. The main
source of common mode error is a roll-over voltage caused by the reference capacitor losing or gaining charge to
stray capacity on its nodes. If there is a large common mode voltage, the reference capacitor can gain charge
(increase voltage) when called up to de-integrate a positive signal but lose charge (decrease voltage) when called up
to de-integrate a negative input signal. This difference in reference for positive or negative input voltage will give a
roll-over error. However, by selecting the reference capacitor such that it is large enough in comparison to the stray
capacitance, this error can be held to less than 0.5 count worst case. (See Component Value Selection)
31
IN HI
32
COMMON
30
IN LO
STRAY
CREF +
V+
34
10μ A
CREF
REF HI
36
A-Z
REF LO
35
A-Z
STRAY
CREF -
33
-
+
RINT
BUFFER
V+
28 1 29
CAZ
A-Z
CINT
INT
27
INTEGRATOR
2.8V
-
-
+
+
INT
A-Z
DE-
DE+
DE+
DE-
INPUT
HIGH
N
-
+
A-Z
6.2V
COMPARATOR
INT
A-Z AND DE(±)
INPUT
LOW
V-
Fig.1 Analog Section
TO
DIGITAL
SECTION
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
8 of 18
QW-R502-018.E