INTERSIL ICM7226A

ICM7226A,
ICM7226B
8-Digit, Multi-Function,
Frequency Counter/Timer
August 1997
Features
Description
• CMOS Design for Very Low Power
The ICM7226 is a fully integrated Universal Counter and
LED display driver. It combines a high frequency oscillator, a
decade timebase counter, an 8-decade data counter and
latches, a 7-segment decoder, digit multiplexer and segment
and digit drivers which can directly drive large LED displays.
The counter inputs accept a maximum frequency of 10MHz
in frequency and unit counter modes and 2MHz in the other
modes. Both inputs are digital inputs. In many applications,
amplification and level shifting will be required to obtain
proper digital signals for these inputs.
• Output Drivers Directly Drive Both Digits and
Segments of Large 8-Digit LED Displays
• Measures Frequencies from DC to 10MHz; Periods
from 0.5µs to 10s
• Stable High Frequency Oscillator uses either 1MHz or
10MHz Crystal
• Both Common Anode and Common Cathode Available
• Control Signals Available for External Systems
Interfacing
• Multiplexed BCD Outputs
Applications
• Frequency Counter
• Period Counter
• Unit Counter
• Frequency Ratio Counter
• Time Interval Counter
Ordering Information
PART NUMBER
TEMP.
RANGE (oC)
PACKAGE
PKG.
NO.
ICM7226AlJL
-25 to 85
40 Ld CERDIP
F40.6
ICM7226BlPL
-25 to 85
40 Ld PDIP
E40.6
The ICM7226 can function as a frequency counter, period
counter, frequency ratio (fA/fB) counter, time interval counter
or as a totalizing counter. The devices require either a
10MHz or 1MHz quartz crystal timebase, or if desired an
external timebase can also be used. For period and time
interval, the 10MHz timebase gives a 0.1µs resolution. In
period average and time interval average, the resolution can
be in the nanosecond range. In the frequency mode, the
user can select accumulation times of 0.01s, 0.1s, 1s and
10s. With a 10s accumulation time, the frequency can be displayed to a resolution of 0.1Hz. There is 0.2s between measurements in all ranges. Control signals are provided to
enable gating and storing of prescaler data.
Leading zero blanking has been incorporated with frequency
display in kHz and time in µs. The display is multiplexed at a
500Hz rate with a 12.2% duty cycle for each digit. The
ICM7226A is designed for common anode displays with typical peak segment currents of 25mA, and the ICM7226B is
designed for common cathode displays with typical segment
currents of 12mA. In the display off mode, both digit drivers
and segment drivers are turned off, allowing the display to
be used for other functions.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
http://www.intersil.com or 407-727-9207 | Copyright © Intersil Corporation 1999
9-15
File Number
3169.1
ICM7226A, ICM7226B
Pinouts
ICM7226A
COMMON ANODE (CERDIP)
TOP VIEW
CONTROL INPUT
1
40 INPUT A
INPUT B
2
39 HOLD
MEASUREMENT IN PROGRESS
3
38 BUF OSC OUT
FUNCTION
4
37 NC (NOTE 1)
STORE
5
36 OSC OUT
BCD 4
6
35 OSC IN
BCD 8
7
34 NC (NOTE 1)
DP
8
33 EXT OSC IN
SEG e
9
32 RST OUT
SEG g 10
31 EXT RANGE
SEG a 11
30 D1
VSS 12
29 D2
SEG d 13
28 D3
SEG b 14
27 D4
SEG c 15
26 D5
SEG f 16
25 VDD
BCD 2 17
24 D6
BCD 1 18
23 D7
RST INPUT 19
22 D8
EXT DP IN 20
21 RANGE
ICM7226B
COMMON CATHODE (PDIP)
TOP VIEW
CONTROL INPUT
1
40 INPUT A
INPUT B
2
39 HOLD
MEASUREMENT IN PROGRESS
3
38 BUF OSC OUT
FUNCTION
4
37 NC (NOTE 1)
STORE
5
36 OSC OUT
BCD 4
6
35 OSC IN
BCD 8
7
34 NC (NOTE 1)
D1
8
33 EXT OSC IN
D3
9
32 RST OUT
D2 10
31 EXT RANGE
D4 11
30 DP OUT
VSS 12
29 SEG g
D5 13
28 SEG e
D6 14
27 SEG a
D7 15
26 SEG d
D8 16
25 VDD
BCD 2 17
24 SEG b
BCD 1 18
23 SEG c
RST INPUT 19
22 SEG f
EXT DP IN 20
21 RANGE
NOTE:
1. For maximum frequency stability, connect to VDD or VSS .
9-16
ICM7226A, ICM7226B
Functional Block Diagram
8
DECODER
8
DIGIT
DRIVERS
REFERENCE
COUNTER
+103
3
RANGE
CONTROL
LOGIC
EXT OSC
INPUT
OSC
INPUT
104 OR
105
OSC
SELECT
STORE
AND RESET
LOGIC
100Hz
OSC
OUTPUT
RANGE
SELECT
LOGIC
CONTROL
LOGIC
6
RESET
INPUT
INPUT A
4
INPUT B
4
DP
LOGIC
OVERFLOW
4
4
4
4
EXT
DP
INPUT
4
DATA LATCHES
STORE
OUTPUT MUX
8
Q
D
INPUT
CONTROL
LOGIC
4
CONTROL
INPUT
RESET
MAIN
EN COUNTER
÷103
CL
INPUT
CONTROL
LOGIC
RANGE
INPUT
EXT RANGE
INPUT
5
BUF OSC
OUTPUT
DIGIT
OUTPUTS
(8)
CL
DECODER
AND LZB
LOGIC
4
7
SEGMENT
DRIVERS
8
SEGMENT
OUTPUTS
(8)
MAIN
FF
R
FUNCTION
INPUT
4
FN
CONTROL
LOGIC
4
BCD
OUTPUTS
(4)
RESET
OUTPUT
6
MEAS IN
PROGRESS
OUTPUT
STORE
OUTPUT
HOLD
INPUT
9-17
ICM7226A, ICM7226B
Absolute Maximum Ratings
Thermal Information
Maximum Supply Voltage (VDD - VSS). . . . . . . . . . . . . . . . . . . . 6.5V
Maximum Digit Output Current . . . . . . . . . . . . . . . . . . . . . . . . 400mA
Maximum Segment Output Current . . . . . . . . . . . . . . . . . . . . . 60mA
Voltage On Any Input or
Output Terminal (Note 1) . . . . . . . . . . . . . . VDD +0.3V to VSS -0.3V
Thermal Resistance (Typical, Note 2)
θJA (oC/W) θJC (oC/W)
CERDIP Package . . . . . . . . . . . . . . . .
45
9
PDIP Package . . . . . . . . . . . . . . . . . . .
50
N/A
Maximum Junction Temperature
CERDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175oC
PDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150oC
Maximum Storage Temperature Range . . . . . . . . . .-55oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300oC
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . -25oC to 85oC
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation
of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES:
1. Destructive latchup may occur if input signals are applied before the power supply is established or if inputs or outputs are forced to
voltages exceeding VDD or VSS by 0.3V.
2. θJA is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
VDD = 5.0V, TA = 25oC, Unless Otherwise Specified
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
-
2
5
mA
4.75
-
6.0
V
-25oC to 85oC
4.75V < VDD < 6.0V, Figure 9
Function = Frequency, Ratio,
Unit Counter
10
14
-
MHz
Function = Period, Time Interval
2.5
-
-
MHz
-25oC to 85oC
2.5
-
-
MHz
250
-
-
ns
0.1
-
10
MHz
2000
-
-
µS
Operating Supply Current, IDD
Display Off, Unused Inputs to VSS
Supply Voltage Range (VDD -VSS), VSUPPLY
-25oC to 85oC, INPUT A,
INPUT B Frequency at fMAX
Maximum Frequency INPUT A, Pin 40, fA(MAX)
Maximum Frequency INPUT B, Pin 2, fB(MAX)
4.75V < VDD < 6.0V, Figure 10
Minimum Separation INPUT A to INPUT B,
Time Interval Function
-25oC to 85oC
4.75V < VDD < 6.0V, Figure 1
Oscillator Frequency and External Oscillator Frequency, -25oC to 85oC
4.75V < VDD < 6.0V
fOSC
Oscillator Transconductance, gM
VDD -4.75V, TA = 85oC
Multiplex Frequency, fMUX
fOSC = 10MHz
-
500
-
Hz
Time Between Measurements
fOSC = 10MHz
-
200
-
ms
Input Rate of Charge, dVIN/dt
Inputs A, B
-
15
-
mV/µs
-25oC to 85oC
-
-
1.0
V
3.5
-
-
V
-
-
20
µA
Input Voltages: Pins 2, 19, 33, 39, 40, 35
Input Low Voltage, VIL
Input High Voltage, VlH
Pins 2, 39, 40, Input Leakage, A, B, IILK
Input Resistance to VDD Pins 19, 33, RIN
VIN = VDD -1.0V
100
400
-
kΩ
Input Resistance to VSS Pin 31, RIN
VIN = +1.0V
50
100
-
kΩ
Low Output Current, Pins 3, 5-7, 17, 18, 32, 38, IOL
VOL = +0.4V
400
-
-
µA
High Output Current, Pins 5-7, 17, 18, 32, HOL
VOH = +2.4V
100
-
-
µA
High Output Current, Pins 3, 38, HOL
VOH = VDD -0.8V
265
-
-
µA
Low Output Current, IOL
VO = +1.5V
25
35
-
mA
High Output Current, IOH
VO = VDD -1.0V
-
100
-
µA
Output Current
ICM7226A
Segment Driver: Pins 8-11, 13-16
9-18
ICM7226A, ICM7226B
Electrical Specifications
VDD = 5.0V, TA = 25oC, Unless Otherwise Specified (Continued)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Input Low Voltage, VIL
-
-
0.8
V
Input High Voltage, VIH
2.0
-
-
V
VIN = +1.0V
50
100
-
kΩ
Low Output Current, IOL
VO = +1.0V
-
-0.3
-
mA
High Output Current, IOH
VO = VDD -2.0V
150
180
-
mA
-
-
10
µA
10
15
-
mA
Input Low Voltage, VIL
-
-
VDD-2.0
V
Input High Voltage, VIH
VDD-0.8
-
-
V
VIN = VDD -1.0V
100
360
-
kΩ
Low Output Current, IOL
VO = +1.0V
50
75
-
mA
High Output Current, IOH
VO = VDD -2.5V
-
100
-
µA
Multiplex Inputs: Pins 1, 4, 20, 21
Input Resistance to VSS, RIN
Digit Driver: Pins 22-24, 26-30
ICM7226B
Segment Driver: Pins 22-24, 26-30
Leakage Current, IL
VO = VSS
High Output Current, IOH
VO = VDD -2.0V
Multiplex Inputs: Pins 1, 4, 20, 21
Input Resistance to VSS, RIN
Digit Driver: Pins 8-11, 13-16
NOTES:
1. Assumes all leads soldered or welded to PC board and free air flow.
2. Typical values are not tested.
Timing Waveform
40ms
STORE
30ms TO 40ms
60ms
RESET
40ms
UPDATE
190ms TO 200ms
FUNCTION:
TIME INTERVAL
UPDATE
PRIMING
MEASUREMENT INTERVAL
MEASUREMENT
IN PROGRESS
INPUT A
PRIMING EDGES
INPUT B
250ns MIN
MEASURED
INTERVAL
(FIRST)
NOTE:
MEASURED
INTERVAL
(LAST)
1. If range is set to 1 event, first and last measured interval will coincide.
FIGURE 1. WAVEFORMS FOR TIME INTERVAL MEASUREMENT (OTHERS ARE SIMILAR, BUT WITHOUT PRIMING PHASE)
9-19
ICM7226A, ICM7226B
Typical Performance Curves
200
300
TA = 25oC
4.5 ≤ VDD ≤ 6.0V
VDD = 5.5V
50
200
VDD = 4.5V
IDIG (mA)
IDIGIT (mA)
VDD = 5.0V
100
100
50
25oC
85oC
-20oC
0
0
0
1
2
0
3
1
VOUT (V)
FIGURE 2. ICM7226B TYPICAL IDIGIT vs VOUT
30
2
3
VDD-VOUT (V)
FIGURE 3. ICM7226A TYPICAL IDIG vs VDD-VOUT
80
4.5 ≤ VDD ≤ 6.0V
TA = 25oC
-20oC
VDD = 5.5V
25oC
60
VDD = 5.0V
20
ISEG (mA)
ISEG (mA)
85oC
VDD = 4.5V
40
10
20
0
0
0
1
2
0
3
1
2
FIGURE 4. ICM7226B TYPICAL ISEG vs VDD-VOUT
FIGURE 5. ICM7226A TYPICAL ISEG vs VOUT
200
80
-20oC
VDD = 5.0V
VDD = 5.0V
-20oC
25oC
25oC
60
ISEG (mA)
IDIGIT (mA)
150
85oC
100
85oC
40
20
50
0
3
VOUT (V)
VDD-VOUT (V)
0
0
1
2
3
0
VOUT (V)
1
2
VOUT (V)
FIGURE 6. ICM7226B TYPICAL IDIGIT vs VOUT
FIGURE 7. ICM7226A TYPICAL ISEG vs VOUT
9-20
3
ICM7226A, ICM7226B
Typical Performance Curves
(Continued)
20
fA (MAX) FREQUENCY UNIT COUNTER,
FREQUENCY RATIO MODES
FREQUENCY (MHz)
15
10
fA (MAX) fB (MAX) PERIOD
TIME INTERVAL MODES
5
TA = 25oC
0
3
4
5
6
VDD-VSS (V)
FIGURE 8. fA(MAX), fB(MAX) AS A FUNCTION OF SUPPLY
Description
INPUTS A and B
The signal to be measured is applied to INPUT A in
frequency period, unit counter, frequency ratio and time
interval modes. The other input signal to be measured is
applied to INPUT B in frequency ratio and time interval. fA
should be higher than fB during frequency ratio.
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.
COUNTED
TRANSITIONS
Multiplexed Inputs
50ns MIN
INPUT A
Both inputs are digital inputs with a typical switching threshold of 2.0V at VDD = 5.0V and input impedance of 250kΩ.
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
4.5V
0.5V
tr = tf = 10ns
50ns MIN
FIGURE 9. WAVEFORM FOR GUARANTEED MINIMUM fA(MAX)
FUNCTION = FREQUENCY, FREQUENCY RATIO,
UNIT COUNTER
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.
MEASURED
INTERVAL
250ns
MIN
INPUT A OR 4.5V
INPUT B 0.5V
250ns
MIN
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 high for the common anode lCM7226A and active low
for the common cathode lCM7226B.
tr = tf = 10s
FIGURE 10. WAVEFORM FOR GUARANTEED MINIMUM fB(MAX)
AND fA(MAX) FOR FUNCTION = PERIOD AND
TIME INTERVAL
9-21
ICM7226A, ICM7226B
Table 1 shows the functions selected by each digit for these
inputs.
TABLE 1. MULTIPLEXED INPUT FUNCTIONS
INPUT
FUNCTION
FUNCTION INPUT
Pin 4
RANGE INPUT
Pin 21
CONTROL INPUT
Pin 1
DIGIT
Frequency
D1
Period
D8
Frequency Ratio
D2
Time Interval
D5
Unit Counter
D4
Oscillator Frequency
D3
0.01s/1 Cycle
D1
0.1s/10 Cycles
D2
1s/100 Cycles
D3
10s/1K Cycles
D4
Enable External Range Input
D5
Display Off
D4 and
Hold
The implementation of different functions is done by routing
the different signals to two counters, called “Main Counter”
and “Reference Counter”. A simplified block diagram of the
device for functions realization is shown in Figure 11. Table 2
shows which signals will be routed to each counter in different cases. The output of the Main Counter is the information
which goes to the display. The Reference Counter divides its
input to 1, 10, 100 and 1000. One of these outputs will be
selected through the range selector and drive the enable
input of the Main Counter. This means that the Reference
Counter, along with its' associated blocks, directs the Main
Counter to begin counting and determines the length of the
counting period. Note that Figure 11 does not show the complete functional diagram (See the Functional Block Diagram). After the end of each counting period, the output of
the Main Counter will be latched and displayed, then the
counter will be reset and a new measurement cycle will
begin. Any change in the FUNCTION INPUT will stop the
present measurement without updating the display and then
initiate a new measurement. This prevents an erroneous first
reading after the FUNCTION INPUT is changed. In all
cases, the 1-0 transitions are counted or timed.
TABLE 2. INPUT ROUTING
Display Test
D8
1MHz Select
D2
External Oscillator Enable
D1
Frequency (fA)
Input A
100Hz (Oscillator ÷105 or 104)
External Decimal Point
Enable
D3
Period (tA)
Oscillator
Input A
Ratio (fA /fB)
Input A
Input B
Time Interval
(A→B)
Oscillator
Input A
Input B
Function Input
Unit Counter
(Count A)
Input A
Not Applicable
The six functions that can be selected are: Frequency,
Period, Time Interval, Unit Counter, Frequency Ratio and
Oscillator Frequency.
Osc. Freq.
(fOSC)
Oscillator
100Hz (Oscillator ÷105 or 104)
External DP INPUT
Pin 20
FUNCTION
Decimal point is output for same digit
that is connected to this input.
INTERNAL CONTROL
MAIN
COUNTER
COUNTER
INTERNAL CONTROL
100Hz
INPUT A
INPUT
SELECTOR
CLOCK
INPUT B
REFERENCE COUNTER
÷ 1 ÷ 10 ÷ 100 ÷ 1000
INTERNAL CONTROL
INTERNAL OR
EXTERNAL
OSCILLATOR
INPUT A
INTERNAL CONTROL
RANGE SELECTOR
ENABLE
INPUT
SELECTOR
CLOCK
MAIN COUNTER
FIGURE 11. SIMPLIFIED BLOCK DIAGRAM OF FUNCTIONS IMPLEMENTATION
9-22
ICM7226A, ICM7226B
Frequency - In this mode input A is counted by the Main
Counter for a precise period of time. This time is determined
by the time base oscillator and the selected range. For the
10MHz (or 1MHz) time base, the resolutions are 100Hz,
10Hz, 1Hz and 0.1Hz. The decimal point on the display is
set for kHz reading.
Period - In this mode, the timebase oscillator is counted by
the Main Counter for the duration of 1, 10, 100 or 1000
(range selected) periods of the signal at input A. A 10MHz
timebase gives resolutions of 0.1µs to 0.0001µs for 1000
periods averaging. Note that the maximum input frequency
for period measurement is 2.5MHz.
Frequency Ratio - In this mode, the input A is counted by
the Main Counter for the duration of 1, 10, 100 or 1000
(range selected) periods of the signal at input B. The frequency at input A should be higher than input B for meaningful result. The result in this case is unitless and its resolution
can go up to 3 digits after decimal point.
Time Interval - In this mode, the timebase oscillator is counted
by the Main Counter for the duration of a 1-0 transition of input
A until a 1-0 transition of input B. This means input A starts the
counting and input B stops it. If other ranges, except 0.01s/1
cycle are selected the sequence of input A and B transitions
must happen 10, 100 or 1000 times until the display becomes
updated; note this when measuring long time intervals to give
enough time for measurement completion. The resolution in
this mode is the same as for period measurement. See the
Time Interval Measurement section also.
Unit Counter - In this mode, the Main Counter is always
enabled. The input A is counted by the Main Counter and
displayed continuously.
Oscillator Frequency - In this mode, the device makes a
frequency measurement on its timebase. This is a self test
mode for device functionality check. For 10MHz timebase
the display will show 10000.0, 10000.00, 10000.000 and
Overflow in different ranges.
Range Input
The RANGE INPUT selects whether the measurement period is
made for 1,10,100 or 1000 counts of the Reference Counter or it
is controlled by EXT RANGE input. As it is shown in Table 1, this
gives different counting windows for frequency measurement
and various cycles for other modes of measurement.
In all functional modes except Unit Counter, any change in
the RANGE INPUT will stop the present measurement without updating the display and then initiate a new measurement. This prevents an erroneous first reading after the
RANGE INPUT is changed.
Control Input
Unlike the other multiplexed inputs, to which only one of the
digit outputs can be connected at a time, this input can be
tied to different digit lines to select combination of controls.
In this case, isolation diodes must be used in digit lines to
avoid crosstalk between them (see Figure 19). The direction
of diodes depends on the device version, common anode or
common cathode. For maximum noise immunity at this input,
in addition to the 10K resistor which was mentioned before,
a 39pF to 100pF capacitor should also be placed between
this input and the VDD or VSS (See Figure 19).
Display Off - To disable the display drivers, it is necessary to tie
the D4 line to the CONTROL INPUT and have the HOLD input
at VDD . While in Display Off mode, the segments and digit drivers are all off, leaving the display lines floating, so the display
can be shared with other devices. In this mode, the oscillator
continues to run with a typical supply current of 1.5mA with a
10MHz crystal, but no measurements are made and multiplexed inputs are inactive. A new measurement cycle will be initiated when the HOLD input is switched to VSS .
Display Test - Display will turn on with all the digits showing
8s and all decimal points also on. The display will be blanked
if Display Off is selected at the same time.
1MHz Select - The 1MHz select mode allows use of a 1MHz
crystal with the same digit multiplex rate and time between
measurement as with a 10MHz crystal. This is done by dividing the oscillator frequency by 104 rather than 105. The decimal point is also shifted one digit to the right in period and
time interval, since the least significant digit will be in µs
increment rather than 0.1µs increment.
External Oscillator Enable - In this mode, the signal at EXT
OSC INPUT is used as a timebase instead of the on-board
crystal oscillator (built around the OSC INPUT, OSC OUTPUT
inputs). This input can be used for an external stable temperature compensated crystal oscillator or for special measurements with any external source. The on-board crystal oscillator
continues to work when the external oscillator is selected. This
is necessary to avoid hang-up problems, and has no effect on
the chip's functional operation. If the on-board oscillator frequency is less than 1MHz or only the external oscillator is used,
THE OSC INPUT MUST BE CONNECTED TO THE EXT OSC
INPUT providing the timebase has enough voltage swing for
OSC INPUT (See Electrical Specifications). If the external timebase is TTL level a pullup resistor must be used for OSC
INPUT. The other way is to put a 22MΩ resistor between OSC
INPUT and OSC OUTPUT and capacitively couple the EXT
OSC INPUT to OSC INPUT. This will bias the OSC INPUT at
its threshold and the drive voltage will need to be only 2VP-P .
The external timebase frequency must be greater than 100kHz
or the chip will reset itself to enable the on-board oscillator.
External Decimal Point Enable - In this mode, the EX
INPUT is enabled. A decimal point will be displayed for
digit that its output line is connected to this input (EX
INPUT). Digit 8 should not be used since it will override
overflow output. Leading zero blanking is effective for
digits to the left of selected decimal point.
DP
the
DP
the
the
Hold Input
Except in the unit counter mode, when the HOLD input is
at VDD , any measurement in progress (before STORE goes
low) is stopped, the main counter is reset and the chip is
held ready to initiate a new measurement as soon as HOLD
goes low. The latches which hold the main counter data are
not updated, so the last complete measurement is displayed.
In unit counter mode when HOLD input is at VDD , the
counter is not stopped or reset, but the display is frozen at
that instantaneous value. When HOLD goes low the count
continues from the new value in the new counter.
9-23
ICM7226A, ICM7226B
RST IN Input
190ms TO 200ms
MEAS
IN PROGRESS
The RST IN is provided to reset the Main Counter, stop any
measurement in progress, and enable the display latches,
resulting in the all zero display. It is suggested to have a
capacitor at this input to VSS to prevent any hangup problem
on power up. See application circuits.
40ms
STORE
30ms TO
40ms
60ms
RESET OUT
EXT RANGE Input
40ms
This input is provided to select ranges other than those
provided in the chip. In any mode of measurement the duration
of measurement is determined by the EXT RANGE if this input
is enabled. This input is sampled at 10ms intervals by the
100Hz reference derived from the timebase. Figure 12 shows
the relationship between this input, 100Hz reference signal and
MEAS IN PROGRESS. EXT RANGE can change state
anywhere during the period of 100Hz reference by will be
sampled at the trailing edge of the period to start or stop
measurement.
REFERENCE
COUNTER
CLOCK
MEAS
IN PROGRESS
tr
FIGURE 13. RESET OUT, STORE AND MEASUREMENT IN
PROGRESS OUTPUTS BETWEEN MEASUREMENTS
BCD Outputs
The BCD representation of each display digit is available at
the BCD outputs in a multiplexed fashion. See Table 3 for digits truth table. The BCD output of each digit is available when
its corresponding digit output is activated. Note that the digit
outputs are multiplexed from D8 (MSD) to D1 (LSD). The positive going (ICM7226A, common anode) or the negative going
(ICM7226B, common cathode) digit drive signals lag the BCD
data by 2µs to 6µs. This starting edge of each digit drive signal should be used to externally latch the BCD data. Each
BCD output drives one low power Schottky TTL load. Leading
zero blanking has no effect on the BCD outputs.
TABLE 3. TRUTH TABLE BCD OUTPUTS
EXT RANGE
INPUT
FIGURE 12. EXTERNAL RANGE INPUT TO END OF
MEASUREMENT IN PROGRESS
NUMBER
BCD 8
PIN 7
BCD 4
PIN 6
BCD 2
PIN 17
BCD 1
PIN 18
0
0
0
0
0
1
0
0
0
1
2
0
0
1
0
3
0
0
1
1
4
0
1
0
0
5
0
1
0
1
6
0
1
1
0
7
0
1
1
1
8
1
0
0
0
9
1
0
0
1
This input should not be used for short arbitrary ranges
(because of its sampling period), it is provided for very long
gating purposes. A way of using the ICM7226 for a short
arbitrary range is to feed the gating signal into the INPUT B
and run the device in the Frequency Ratio mode. Note that
the gating period will be from one positive edge until the next
positive edge of INPUT B (0.01s/1 cycle range).
MEAS IN PROGRESS, STORE, RST OUT Outputs
These outputs are provided for external system interfacing.
MEAS IN PROGRESS stays low during measurements and
goes high for intervals between measurements. Figure 13
shows the relationship between these outputs for intervals
between measurements. All these outputs can drive a low
power Schottky TTL. The MEAS IN PROGRESS can drive
one ECL load if the ECL device is powered from the same
power supply as the ICM7226.
BUF OSC OUT Output
The BUFFered OSCillator OUTput is provided for use of the
on-board oscillator signal, without loading the oscillator itself.
This output can drive one low power Schottky TTL load. Care
should be taken to minimize capacitive loading on this pin.
Decimal Point Position
Table 4 shows the decimal point position for different modes
of lCM7226 operation. Note that the digit 1 is the least significant digit. Table is given for 10MHz timebase frequency.
TABLE 4. DECIMAL POINT POSITIONS
FREQUENCY
PERIOD
FREQUENCY
RATIO
TIME
INTERVAL
UNIT
COUNTER
OSCILLATOR
FREQUENCY
0.01s/1 Cycle
D2
D2
D1
D2
D1
D2
0.1s/10 Cycle
D3
D3
D2
D3
D1
D3
1s/100 Cycle
D4
D4
D3
D4
D1
D4
RANGE
10s/1K Cycle
D5
D5
D4
D5
D1
D5
External
N/A
N/A
N/A
N/A
N/A
N/A
9-24
ICM7226A, ICM7226B
Overflow Indication
When overflow happens in any measurement it will be indicated
on the decimal point of the digit 8. A separate LED indicator can
be used. Figure 14 shows how to connect this indicator.
When timing repetitive signals, it is not necessary to “prime”
the lCM7226A and lCM7226B as the first alternating signal
states automatically prime the device. See Figure 1.
During any time interval measurement cycle, the ICM7226A
and lCM7226B requires 200ms following B going low to
update all internal logic. A new measurement cycle will not
take place until completion of this internal update time.
Oscillator Considerations
a
f
b
g
e
c
DP
d
LED overflow indicator connections: Overflow will be
indicated on the decimal point output of digit 8.
DEVICE
For a specific crystal and load capacitance, the required gM
can be calculated as follows:
CATHODE
ANODE
ICM7226A
Decimal Point
D8
ICM7226B
D8
Decimal Point
CO 2

2
g M = ω C IN C OUT R S 1 + -------- 
CL 

 C IN C OUT 
where C L =  --------------------------------- 
 C IN + C OUT 
FIGURE 14. SEGMENT IDENTIFICATION AND DISPLAY FONT
Time Interval Measurement
When in the time interval mode and measuring a single
event, the lCM7226A and lCM7226B must first be “primed”
prior to measuring the event of interest. This is done by first
generating a negative going edge on Channel A followed by a
negative going edge on Channel B to start the “measurement
interval”. The inputs are then primed ready for the measurement. Positive going edges on A and B, before or after the
priming, will be needed to restore the original condition.
Priming can be easily accomplished using the circuit in
Figure 15.
SIGNAL A
2
INPUT A
2
INPUT B
VDD
PRIME
N.O.
1
1
1
10K
RS = Crystal Series Resistance
CIN = Input Capacitance
COUT = Output Capacitance
ω = 2πf
The required gM should not exceed 50% of the gM specified
for the lCM7226 to insure reliable startup. The OSCillator
INPUT and OUTPUT pins each contribute about 4pF to CIN
and COUT . For maximum stability of frequency, CIN and
COUT should be approximately twice the specified crystal
static capacitance.
f OSC
f OSC
f MUX = ------------------- for 10MHz mode and f MUX = ------------------- for the
4
3
2 × 10
2 × 10
6
2 × 10
1MHz mode. The time between measurements is ------------------- in
f OSC
150K
1
CO = Crystal Static Capacitance
In cases where non decade prescalers are used, it may be
desirable to use a crystal which is neither 10MHz or 1MHz.
In that case both the multiplex rate and time between
measurements will be different. The multiplex rate is:
SIGNAL B
VDD
The oscillator is a high gain complementary FET inverter. An
external resistor of 10MΩ or 22MΩ should be connected
between the oscillator input and output to provide biasing.
The oscillator is designed to work with a parallel resonant
10MHz quartz crystal with a static capacitance of 22pF and
a series resistance of less than 35Ω. Among suitable
crystals is the 10MHz CTS KNIGHTS ISI-002.
5
2 × 10
the 10MHz mode and ------------------- in the 1MHz mode.
1N914
100K
0.1µF
VSS
VSS
DEVICE
f OSC
10nF
VSS
The buffered oscillator output should be used as an oscillator
test point or to drive additional logic; this output will drive one
low power Schottky TTL load. When the buffered oscillator
output is used to drive CMOS or the external oscillator input,
a 10kΩ resistor should be added from the buffered oscillator
output to VDD .
TYPE
1
CD4049B Inverting Buffer
2
CD4070B Exclusive - OR
FIGURE 15. PRIMING CIRCUIT, SIGNALS A AND B BOTH HIGH
OR LOW
Following the priming procedure (when in single event or 1
cycle range) the device is ready to measure one (only) event.
The crystal and oscillator components should be located as
close to the chip as practical to minimize pickup from other
signals. Coupling from the EXTERNAL OSClLLATOR INPUT
to the OSClLLATOR OUTPUT or INPUT can cause
undesirable shifts in oscillator frequency.
9-25
ICM7226A, ICM7226B
Display Considerations
The display is multiplexed at a 500Hz rate with a digit time of
244µs. An interdigit blanking time of 6µs is used to prevent
display ghosting (faint display of data from previous digit
superimposed on the next digit). Leading zero blanking is
provided, which blanks the left hand zeroes after decimal
point or any non zero digits. Digits to the right of the decimal
point are always displayed. The leading zero blanking will be
disabled when the Main Counter overflows.
The lCM7226A is designed to drive common anode LED displays at peak current of 25mA/segment, using displays with
VF = 1.8V at 25mA. The average DC current will be greater
than 3mA under these conditions. The lCM7226B is designed
to drive common cathode displays at peak current of
15mA/segment using displays with VF = 1.8V at 15mA. Resistors can be added in series with the segment drivers to limit
the display current, if required. The Typical Performance
Curves show the digit and segment currents as a function of
output voltage for common anode and common cathode
drivers.
To increase the light output from the displays, VDD may be
increased to 6.0V. However, care should be taken to see that
maximum power and current ratings are not exceeded.
The SEGment and Digit outputs in both the ICM7226A and
ICM7226B are not directly compatible with either TTL or
Accuracy
In a Universal Counter, crystal drift and quantization errors
cause errors. In frequency, period and time interval
modes, a signal derived from the oscillator is used in either
the Reference Counter or Main Counter, and in these
modes, an error in the oscillator frequency will cause an
identical error in the measurement. For instance, an oscillator temperature coefficient of 20ppm/oC will cause a measurement error of 20ppm/oC.
In addition, there is a quantization error inherent in any digital measurement of ±1 count. Clearly this error is reduced by
displaying more digits. In the frequency mode maximum
accuracy is obtained with high frequency inputs and in
period mode maximum accuracy is obtained with low frequency inputs. As can be seen in Figure 16. In time interval
measurements there can be an error of 1 count per interval.
As a result there is the same inherent accuracy in all ranges
as shown in Figure 17. In frequency ratio measurement
can be more accurately obtained by averaging over more
cycles of INPUT B as shown in Figure 18.
0
0
FREQUENCY MEASURE
MAXIMUM NUMBER OF
SIGNIFICANT DIGITS
MAXIMUM NUMBER OF
SIGNIFICANT DIGITS
CMOS logic. Therefore, level shifting with discrete transistors may be required to use these outputs as logic signals.
External latching should be down on the leading edge of the
digit signal.
0.01s
0.1s
1s
10s
2
4
1 CYCLE
10 CYCLES
102 CYCLES
103 CYCLES
6
1
10
103
FREQUENCY (Hz)
2
MAXIMUM TIME INTERVAL
FOR 103 INTERVALS
3
4
MAXIMUM TIME
INTERVAL FOR
102 INTERVALS
5
6
MAXIMUM TIME INTERVAL
FOR 10 INTERVALS
7
PERIOD MEASURE
fOSC = 10MHz
8
1
8
105
107
1
FIGURE 16. MAXIMUM ACCURACY OF FREQUENCY AND
PERIOD MEASUREMENTS DUE TO LIMITATIONS
OF QUANTIZATION ERRORS
102
10
103
104
105
TIME INTERVAL (µs)
106
107
108
FIGURE 17. MAXIMUM ACCURACY OF TIME INTERVAL
MEASUREMENT DUE TO LIMITATIONS OF
QUANTIZATION ERRORS
0
MAXIMUM NUMBER OF
SIGNIFICANT DIGITS
1
RANGE
2
1 CYCLE
10 CYCLES
102 CYCLES
103 CYCLES
3
4
5
6
7
8
1
10
102
103
104
fA /fB
105
106
107
108
FIGURE 18. MAXIMUM ACCURACY FOR FREQUENCY RATIO MEASUREMENT DUE TO LIMITATION OF QUANTIZATION ERRORS
9-26
ICM7226A, ICM7226B
Test Circuit
DISPLAY DISPLAY
OFF
TEST 1MHz
VDD = 5.0V
EXT OSC IN
EXT
DP
TEST
FUNCTION
GENERATOR
INPUT A
FUNCTION
GENERATOR
EXT
OSC
D4
D8
D2
D1
CONTROL INPUT
D3
D5
1N914s
39pF
VSS
FUNCTION
GENERATOR
10kΩ
1
40
2
39
3
38
4
37
STORE
5
36
BCD C
6
35
BCD D
7
34
DP
8
33
INPUT B
MEAS IN PROGRESS
FUNCTION
10K
D1
D8
D2
D5
D4
D3
e
g
a
HOLD
10MHz
CRYSTAL
VDD
22MΩ
32
10
31
11
30
EXT RANGE
D1
ICM7226A
12
29
D2
d
13
28
D3
b
14
27
D4
c
15
26
D5
f
16
25
BCD B
17
24
D6
BCD A
18
23
D7
19
22
D8
20
21
RESET
6
VDD
RST OUT
9
VDD
BUF OSC OUT
30pF
39pF
VDD
VDD
8
CRYSTAL SPECS. =
FO 10.00MHz
CO 22pF
RS 35Ω
D1
D2
VDD
5
D3
D4
100kΩ
D5
6
D1
D2
D3
D4
100kΩ
8
D5
D6
8
6
D7
LED
OVERFLOW
INDICATOR
a
b
c
d
e
f
g
D8
8
DP
D8
D8
D7
DEVICE
D6
D5
D4
D3
CATHODE
ANODE
ICM7226A
DP
D8
ICM7226B
D8
DP
D2
NOTE: Overflow will be indicated on the decimal point output of digit 7.
FIGURE 19.
9-27
D1
DENOTES BU
WITH 6
CONDUCTORS
ICM7226A, ICM7226B
Typical Applications
The ICM7226 has been designed as a complete stand alone
Universal Counter, or used with prescalers and other circuitry
in a variety of applications. Since INPUT A and INPUT B are
digital inputs, additional circuitry will be required in many
applications, for input buffering, amplification, hysteresis, and
level shifting to obtain the required digital voltages. For many
applications a FET source follower can be used for input buffering, and an ECL 10116 line receiver can be used for amplification and hysteresis to obtain high impedance input,
sensitivity and bandwidth. However, cost and complexity of
this circuitry can vary widely, depending upon the sensitivity
and bandwidth required. When TTL prescalers or input buffers
are used, a pull up resistors to VDD should be used to obtain
optimal voltage swing at INPUTS A and B. If prescalers aren’t
required, the ICM7226 can be used to implement a minimum
component Universal Counter as shown in Figure 20.
For input frequencies up to 40MHz, the circuit shown in
Figure 21 can be used to implement a frequency and
period counter. To obtain the correct value when measuring
frequency and period, it is necessary to divide the 10MHz
oscillator frequency down to 2.5MHz. In doing this the time
between measurements is lengthened to 800ms and the display multiplex rate is decreased to 125Hz.
If the input frequency is prescaled by ten, the oscillator
frequency can remain at either 10MHz or 1MHz, but the
decimal point must be moved. Figure 22 shows use of a ÷10
prescaler in frequency counter mode. Additional logic has
been added to enable the ICM7226 to count the input
directly in period mode for maximum accuracy.
DISPLAY DISPLAY EXT OSC
BLANK
TEST
ENABLE
10kΩ
39pF
VDD
VDD
A IN
100kΩ
1
B IN
10kΩ
D1
D8
D2
D5
D4
D3
40
39
3
38
4
37
5
36
6
35
7
34
V+
8
33
EXT OSC IN
3
10MHz
CRYSTAL
22MΩ
39pF
9
D2
10
D4
11
30
DP
32
31
39pF (TYP)
V+
12
29
D5
13
28
g
e
D6
14
27
a
D7
15
26
D8
16
25
17
24
b
18
23
c
19
22
f
20
21
0.1µF
D1
V+
D3
RESET
D8
1N914s
2
ICM7226B
D4
HOLD
TYPICAL
CRYSTAL
PARAMETERS
CL 22pF
RS 35Ω
V+
8
d
VDD
4
D1
100kΩ
D2
D3
D4
6
a
b
c
d
e
f
g
8
DP
D8
D7
D6
D5
D4
D3
FIGURE 20. 10MHz UNIVERSAL COUNTER
9-28
D2
D1
D8
ICM7226A, ICM7226B
VDD
Q
VDD
P
D
÷2
÷2
CK
Q
DISPLAY
OFF
EXT OSC
ENABLE
DISPLAY
TEST
D8 3
V+
V+
3kΩ
D
P
C
D1
Q
D3
D
Q
3
38
4
37
5
36
6
35
7
34
8
33
9
22MΩ
DP
D5
13
28
D6
14
27
g
e
a
D7
15
26
D8
16
25
17
24
b
18
23
c
19
22
f
20
21
V+
74LS74
D8
D2
3kΩ
d
VDD
4
D1
100kΩ
D2
D3
RESET
D4
a
b
c
d
e
f
g
8
F
VDD
8
0.1
µF
D1
Q
VDD
VDD
P
DP
R
3
8
D8
D7
D6
D5
D4
D3
D2
FIGURE 21. 40MHz FREQUENCY, PERIOD COUNTER
9-29
D1
D8
Q
C
39pF (TYP)
VDD
31
29
P
IC ÷2
CK2
VDD
10MHz
CRYSTAL
39pF
30
D
Q
C
VDD
12
VDD
Q
VDD
32
ICM7226B
P
IC ÷2
CK1
11
Q
100kΩ
D
D4
B IN
C
39
10
V+
P
40
2
VDD
74LS74
VDD
D2
Q
V+
1
A IN
VDD
HOLD
10kΩ
D4
VDD
3kΩ
10kΩ
CK
C
VDD
1N914
D1
VDD
D
Q
C
39pF
P
Q
OVERFLOW
ICM7226A, ICM7226B
VDD
INPUT
EXT
DISPLAY DISPLAY OSC
EN
OFF
TEST
M1
CP ECL11C90 QTTL
CE
MS
10kΩ
74LS00
VDD
39pF
D4
VDD
10kΩ
M1
INPUT
CP ECL11C90 QTTL
CE
MS
V+ 10kΩ
V+ 10kΩ
74LS00
F
D1
D8
P
D2
R
D4
UC
V+ 10kΩ
40
2
39
3
38
4
37
5
36
6
35
D1
VDD
8
10MHz
CRYSTAL
34
VDD
33
e
9
32
EXT OSC IN
39pF
g
10
a
11
30
12
29
d
13
28
b
14
27
D4
c
15
26
D5
f
16
25
17
24
D6
18
23
D7
D2
19
22
D8
20
21
D3
D4
8
8
31
22MΩ
VDD
D1
39pF
(TYP)
VDD
D2
D3
8
VDD
D1
RANGE
5
D5
100kΩ
a
b
c
d
e
f
g
DP
OVERFLOW
D8
D8
D7
D6
D5
FIGURE 22. 100MHz MULTI-FUNCTION COUNTER
9-30
D4
D3
10
kΩ
100kΩ
8
ICM7226A
D2
1N914s
7
S6
2
1
D8
HOLD
DP
4
0.1µF
1MHz
D3
D2
D1 8
ICM7226A, ICM7226B
VDD
M1
CP ECL11C90 QTTL
CE
MS
INPUT
39pF
VDD
DISPLAY DISPLAY
OFF
TEST
10kΩ
VDD
10kΩ
VDD
2N2222
3kΩ
D4
VDD
FUNCTION
SWITCH
OPEN FREQ
CLOSED
PERIOD
VDD
10kΩ
F
D IN
CONT 2
OUT
CD4016
D1
D7 IN
CONT 2
OUT
40
2
39
3
38
4
37
5
36
6
35
7
34
8
33
100kΩ HOLD
10kΩ
1N914s
VDD
3
10MHz
CRYSTAL
VDD
22MΩ
39pF
(TYP)
39pF
9
D2
10
D4
11
30
DP
g
e
a
32
ICM7226B
D1
VDD
D3
31
12
29
D5
13
28
D6
14
27
D7
15
26
D8
16
25
17
24
18
23
c
19
22
f
20
21
N.O.
0.1µF
1
D2
VDD
VDD
d
b
VDD
8
10kΩ
4
D1
D2
D3
RESET
INPUT
D4
a
b
c
d
e
f
g
8
2
D8
D7
D6
D5
D4
D3
D2
D1
D8
OVERFLOW
FIGURE 23. 100MHz FREQUENCY, PERIOD COUNTER
9-31
ICM7226A, ICM7226B
to put the ICM7226 into a hold mode. The HOLD input can
also be used to reduce the time between measurements.
The circuit shown in Figure 25 puts a short pulse into the
HOLD input a short time after STORE goes low. A new measurement will be initiated at the end of the pulse on the
HOLD input. This circuit reduces the time between measurements to about 40ms from 200ms; use of the circuit shown in
Figure 25 on the circuit shown in Figure 21 will reduce the
time between measurements from 800ms to about 160ms.
Figure 23 shows the use of a CD4016 analog multiplexer to
multiplex the digital outputs back to the FUNCTION Input.
Since the CD4016 is a digitally controlled analog transmission
gate, no level shifting of the digit output is required. CD4051s
or CD4052s could also be used to select the proper inputs for
the multiplexed input on the ICM7226 from 2-bit or 3-bit digital
inputs. These analog multiplexers may also be used in systems in which the mode of operation is controlled by a microprocessor rather than directly from front panel switches. TTL
multiplexers such as the 74LS153 or 74LS251 may also be
used, but some additional circuitry will be required to convert
the digit output to TTL compatible logic levels.
Using LCD Display
Figure 26 shows the ICM7226 being interfaced to LCD displays, by using its BCD outputs and 8 digit lines to drive two
ICM7211 display drivers.
The circuit shown in Figure 24 can be used in any of the
circuit applications shown to implement a single measurement mode of operation. This circuit uses the STORE output
STORE
OUTPUT
HOLD
INPUT
100kΩ
S1
100kΩ
S3
VDD
VDD
VDD
100kΩ
100kΩ
S2
STORE
OUTPUT
VDD
FUNCTION
S1
Open-Single Meas Mode Enabled
S2
Closed-Initiate New Measurement
S3
Closed-Hold Input
a
f
b
N.O.
g
e
f
g
e
c
d
+5V
1
a
f
b
g
c
d
FIGURE 25. CIRCUIT FOR REDUCING TIME BETWEEN
MEASUREMENTS
a
b
HOLD
INPUT
HOLD SWITCH
FIGURE 24. SINGLE MEASUREMENT CIRCUIT FOR USE WITH
ICM7226
a
100pF
100pF
SWITCH
f
100kΩ
e
a
b
f
g
e
c
d
a
b
f
g
e
c
d
g
c
e
d
28 SEGMENT LINES
a
22 23 24 26
D8
•
•
f
g
e
c
d
b
g
c
d
e
c
d
+5V
1
5
ICM7211
31 32 33 34
a
b
28 SEGMENT LINES
5
35
f
b
ICM7211
30 29 28 27
27 28 29 30
7
6
17 18
D5
31 32 33 34
27 28 29 30
D8
•
•
ICM7226A
FIGURE 26. 10MHz UNIVERSAL COUNTER SYSTEM WITH LCD DISPLAY
9-32
D1
36 35
ICM7226A, ICM7226B
All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification.
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate
and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which
may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see web site http://www.intersil.com
Sales Office Headquarters
NORTH AMERICA
Intersil Corporation
P. O. Box 883, Mail Stop 53-204
Melbourne, FL 32902
TEL: (407) 724-7000
FAX: (407) 724-7240
EUROPE
Intersil SA
Mercure Center
100, Rue de la Fusee
1130 Brussels, Belgium
TEL: (32) 2.724.2111
FAX: (32) 2.724.22.05
9-33
ASIA
Intersil (Taiwan) Ltd.
Taiwan Limited
7F-6, No. 101 Fu Hsing North Road
Taipei, Taiwan
Republic of China
TEL: (886) 2 2716 9310
FAX: (886) 2 2715 3029