TC820 TelCom Semiconductor, TC820 Datasheet - Page 14

• Manufacturer Part Number: TC820
• Description: 3-3/4 DIGIT A/D CONVERTER WITH FREQUENCY COUNTER AND LOGIC PROBE
• Manufacturer: TelCom Semiconductor

TC820
with respect to the TC820 power source. The analog common
potential of V
The analog common potential has a voltage coefficient of
0.001%/%.
> 7V), analog common is a very stable potential with excellent
temperature stability (typically 35ppm/ C). This potential
can be used to generate the TC820 reference voltage. An
external voltage reference will be unnecessary in most
cases, because of the 35ppm/ C temperature coefficient.
See the applications section for details.
Function Control Input Pin
Functional Description
function control inputs. The control input truth table is shown
in Table I. The high logic threshold is
low logic level is
3-162
Table I. TC820 Control Input Truth Table
NOTES: 1. Logic "0" = DGND
VOLTS
FREQ/
+
system where input signals are not referenced (float)
With a sufficiently high total supply voltage (V
The TC820 operating modes are selected with the
–
X
0
0
1
V IN
V CM
2. Logic "1" = V
Figure 9.
Counter Input
Frequency
Where:
Logic Input
RANGE/
DD
FREQ
+
–
– 3.3V gives a 7V end-of-battery-life voltage.
V
C I = Integration Capacitor
R I = Integration Resistor
X
Integrator Swing (V
0
1
T I= Integration Time =
INPUT
BUFFER
I
Common-Mode Voltage Reduces Available
=
DGND +1.5V.
R I C I
T I
DD
LOGIC
[
V
CM
1
0
0
0
R I
–
V
COM
IN
TC820
Function
Logic Probe
A/D Converter,
V
A/D Converter,
V
Frequency Counter
[
FULL SCALE
FULL SCALE
–
+
4000
f
OSC
V
V
IN
C I
INTEGRATOR
DD
)
- 1.5V and the
= 2
= 20
DD
V
– V
V
REF
V I
REF
SS
FREQ/VOLTS
analog-to-digital conversion mode or in the frequency counter
mode. When FREQ/VOLTS is connected to V
will measure frequency at the RANGE/FREQ input. When
unconnected, or connected to DGND, the TC820 will oper-
ate as an analog-to-digital converter. This input has an
internal 5 A pull-down to DGND.
LOGIC
function. When connected to V
logic probe mode. The LCD will show "OL" and all decimal
points will be off. The decimal point inputs directly control
"high" and "low" display annunciators. When LOGIC is
unconnected, or connected to DGND, the TC820 will per-
form analog-to-digital or frequency measurements as se-
lected by the FREQ/VOLTS input. The LOGIC input has an
internal 5 A pull-down to DGND.
RANGE/FREQ
the FREQ/VOLTS input. When FREQ/VOLTS is connected
to V
function. Pulses at this input are counted with a time base
equal to f
(V
mended.
selected, connecting RANGE/FREQ to V
integration time by 10. Therefore, the RANGE/FREQ input
can be used to perform a 10:1 range change without
changing external components.
DP0/LO, DP1/HI
by the LOGIC input. When the TC820 is in the analog-to-
digital converter mode, these inputs control the LCD decimal
points. The decimal point truth table is shown in Table II.
These inputs have internal 5 A pull-downs to DGND when
the voltage/frequency measurement mode is active.
Table II. TC820 Decimal Point Truth Table
DD
DD
This input determines whether the TC820 is in the
The LOGIC input is used to activate the logic probe
The function of this dual-purpose pin is determined by
When the TC820 analog-to-digital converter function is
The function of these dual-purpose pins is determined
- 1.5V and DGND +1.5V), an external buffer is recom-
Decimal Point Inputs
DP1
, RANGE/FREQ is the input for the frequency counter
0
0
1
1
OSC
/40,000. Since this input has CMOS input levels
3-3/4 A/D CONVERTER WITH
TELCOM SEMICONDUCTOR, INC.
FREQUENCY COUNTER
DP0
0
1
0
1
AND LOGIC PROBE
DD
, the TC820 will enter the
DD
399.9
39.99
3.999
LCD
3999
DD
will divide the
, the TC820