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| TC530 Datasheet, PDF (12/15 Pages) TelCom Semiconductor, Inc – 5V PRECISION DATA ACQUISITION SUBSYSTEMS | |||
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5V PRECISION DATA ACQUISITION
SUBSYSTEMS
TC530
TC534
3. Calculate LOAD VALUE
LOAD VALUE = 256 â (tINT)(FIN)/1024 = [128]10
[128]10 = 80 hex
4. Calculate RINT
RINT (in Mâ¦) = VINMAX/20 = 2/20 = 100kâ¦
5. Calculate CINT for maximum (4V) integrator out-
put swing
CINT (in µF) = (tINT)(20 x 10 â6)/ (VS â 0.9)
= (.066)(20 x 10 â6)/(4.1)
= .32µF (use closest value: 0.33µF)
NOTE: TelCom recommended capacitor:
WIMA p/n: MK12 .33/63/10
6. Choose CREF and CAZ based on conversion rate
Conversions/sec = 1/(tAZ + tINT + 2tINT + 2msec)
= 1/(66msec + 66msec + 132msec
+ 2msec)
= 3.7 conversions/sec
from which CAZ = CREF = 0.22µF (see Table 1)
NOTE: TelCom recommended capacitor:
WIMA p/n: MK12 .22/63/10
7. Calculate VREF
VREF (in Volts = (VS â 0.9)(CINT)(RINT)
2(tINT)
= (4.1)(0.33x10 â6)(105)/2(.066)
= 1.025V
Power Supply Sequencing
Improper sequencing of the power supply inputs (VDD
vs. VCCD) can potentially cause an improper power-up
sequence to occur. See Circuit Design/Layout Consider-
ations below. Failing to insure a proper power-up sequence
can cause spurious operation.
Ciruit Design/Layout Considerations
(1) Separate ground return paths should be used for the
analog and digital circuitry. Use of ground planes and trace
fill on analog circuit sections is highly recommended
EXCEPT for in and around the integrator section and
CREF, CAZ. (CINT, CREF, CAZ, RINT). Stray capacitance be-
tween these nodes and ground appears in parallel with the
components themselves and can affect measurement accu-
racy.
.01µF
.01µF
VDD
VCCD
1µF
Analog
Inputs
CIN
0.33µF
CAZ
0.22µF
RINT
100k
CREF
0.22µF
MUX
Channel
Control
1µF
IN1 +
IN1 â
IN2+
IN2â
+5V
+5V
RESET
C1
.01µF
10µF
VCCD
VDD
100â¦
(Optional)
EOC
INT
IN3+
IN3â
R/W
DOUT
IN4+
IN4â
CINT
CAZ
BUF
TC534
DIN
DCLK
OSCIN
OSCOUT
VSS
DGND
X1: 2MHz
â5V +5V
1µF
R1
100k
C+REF
CRâEF
A0
A1
CAP+
CAP â
VR+EF
R2
100k
(1.03V)
VRâEF
ACOM
TC04
(1.25V VREF)
I/O
I/O PROCESSOR
I/O
I/O
Figure 6. TC530/534 Typical Application
3-58
TELCOM SEMICONDUCTOR, INC.
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