TC826 データシートの表示（PDF） - TelCom Semiconductor Inc => Microchip
部品番号
コンポーネント説明
メーカー
TC826 Datasheet PDF : 12 Pages
| |||
A/D CONVERTER WITH
BAR GRAPH DISPLAY OUTPUT
1
TC826
THEORY OF OPERATION
Analog Section
In addition to the basic signal integrate and deintegrate
cycles discussed above, the TC826 incorporates an auto-
zero cycle. This cycle removes buffer amplifier, integrator,
and comparator offset voltage error terms from the conver-
sion. A true digital zero reading results without external
adjusting potentiometers. A complete conversion consists
of three cycles: an auto-zero, signal integrate and reference
cycle. (Figures 4 and 5.)
Auto-Zero Cycle
During the auto-zero cycle the differential input signal is
disconnected from the circuit by opening internal analog
gates. The internal nodes are shorted to analog common
(internal analog ground) to establish a zero input condition.
Additional analog gates close a feedback loop around the
integrator and comparator. This loop permits comparator
REF IN
5
CREF
6
7
offset voltage error compensation. The voltage level estab-
2 lished on CAZ compensates for device offset voltages.
The auto-zero cycle length is 19 counts minimum.
Unused time in the deintegrate cycle is added to the auto-
zero cycle.
Signal Integration Cycle
The auto-zero loop is opened and the internal differen-
tial inputs connect to +IN and –IN. The differential input
3 signal is integrated for a fixed time period. The TC826 signal
integration period is 20 clock periods or counts. The exter-
nally set clock frequency is divided by 32 before clocking the
internal counters. The integration time period is:
Where: TSI = 32 x 20
FOSC
FOSC = External Clock Frequency
4
RINT
CAZ
9
10
CINT
11
VDD
8
AZ
3
+ INPUT
INT
AZ
ANALOG 2
COMMON
4
– INPUT
DE–
DE+
DE+
DE–
–
+
BUFFER
AZ
INT
INT
FROM
DIGITAL
CONTROL
SECTION
AZ
INT
DE+
DE–
ANALOG SWITCH
≈ VDD – 2.9V
TC826
INTEGRATOR
–
+
+
–
COMPARATOR
AZ
CMPTR TO DIGITAL
SECTION
VDD
1µA
VDD
≈ 6.3V
5
6
7
TELCOM SEMICONDUCTOR, INC.
12
≈VDD
Figure 4. TC826 Analog Section
8
3-177
Share Link: 