12-BIT µP-COMPATIBLE
ANALOG-TO-DIGITAL CONVERTERS
1
2
3
4
5
6
7
8
TC7109
TC7109A
SERIAL OUTPUT
6402 CMOS UART
RBR1–RBR8
SERIAL INPUT
TBRL DRR TBRE
SFD TBR1–TBR8
2
3
GND
8-BIT DATA BUS
MODE CE/ SEND
LOAD
MODE CE/ SEND
LOAD
MODE CE/ SEND
LOAD
B9–B12
B9–B12
POL, OR
B9–B12
POL, OR
6
6
8
6
8
POL, OR
ANALOG
IN
ANALOG
IN
ANALOG
IN
B1-B8
8
B1–B8
B1–B8
TC7109A
TC7109A
TC7109A
RUN/HOLD
+5V
RUN/HOLD
+5V
RUN/HOLD
LBEN
+5V
HBEN
LBEN
HBEN
LBEN
HBEN
Figure 21. Handshake Interface for Multiplexed Converters
Integrating Converter Features
30
20
10
0
The output of integrating ADCs represents the integral,
or average, of an input voltage over a fixed period of time.
Comparedwithtechniquesinwhichtheinputissampledand
held, theintegratingconverteraveragestheeffectsofnoise.
A second important characteristic is that time is used to
quantizetheanswer,resultinginextremelysmallnonlinearity
errors and no missing output codes. The integrating con-
verter also has very good rejection of frequencies whose
periods are an integral multiple of the measurement period.
This feature can be used to advantage in reducing line
frequency noise (Figure 22).
t = MEASUREMENT
PERIOD
0.1/t
1/t
INPUT FREQUENCY
10/t
Figure 22. Normal Mode Rejection of Dual-Slope Converter as a
Function of Frequency
TELCOM SEMICONDUCTOR, INC.
3-111
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
