ICM7216B_04 Datasheet, PDF (7/18 Pages) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counters/Timers

ICM7216B, ICM7216D
Typical Performance Curves (Continued)
200
V_DD = 5V
150
100
-20^oC
25^oC
85^oC
200
T_A = 25^oC
50
V_DD = 5V
100
V_DD = 5.5V
V_DD = 4.5V
50
50
0
0
1
2
3
V_OUT (V)
FIGURE 4. TYPICAL I_DIGIT vs V_OUT
Description
INPUTS A and B
INPUTS A and B are digital inputs with a typical switching
threshold of 2V at V_DD = 5V. For optimum performance the
peak-to-peak input signal should be at least 50% of the
supply voltage and centered about the switching voltage.
When these inputs are being driven from TTL logic, it is
desirable to use a pullup resistor. The circuit counts high to
low transitions at both inputs. (INPUT B is available only on
lCM7216B).
Note that the amplitude of the input should not exceed the
device supply (above the VDD and below the VSS) by more
than 0.3V, otherwise the device may be damaged.
Multiplexed Inputs
The FUNCTION, RANGE, CONTROL and EXTERNAL
DECIMAL POINT inputs are time multiplexed to select the
function desired. This is achieved by connecting the
appropriate Digit driver output to the inputs. The function,
range and control inputs must be stable during the last half
of each digit output, (typically 125µs). The multiplexed inputs
are active low for the common cathode lCM7216B and
lCM7216D.
Noise on the multiplex inputs can cause improper operation.
This is particularly true when the unit counter mode of
operation is selected, since changes in voltage on the digit
drivers can be capacitively coupled through the LED diodes
to the multiplex inputs. For maximum noise immunity, a
10kΩ resistor should be placed in series with the multiplexed
inputs as shown in the application circuits.
Table 1 shows the functions selected by each digit for
these inputs.
0
0
1
2
3
V_OUT (V)
FIGURE 5. TYPICAL I_DIGIT vs V_OUT
.
TABLE 1. MULTIPLEXED INPUT FUNCTIONS
FUNCTION
DIGIT
FUNCTION INPUT
Frequency
D1
(Pin 3, lCM7216B Only) _Period
D8
Frequency Ratio
D2
Time Interval
D5
Unit Counter
D4
Oscillator Frequency
D3
RANGE INPUT, Pin 14 0.01s/1 Cycle
D1
0.1s/10 Cycles
D2
1s/100 Cycles
D3
10s/1K Cycles
D4
CONTROL INPUT, Pin 1 Display Off
D4 and
Hold
Display Test
D8
1MHz Select
D2
External Oscillator Enable D1
External Decimal Point
D3
Enable
External DP INPUT
Decimal point is output for same digit
(Pin 13, ICM7216D Only) that is connected to this input.
7