Datasheet ICM7216A (Intersil) - 9

ICM7216A, ICM7216B, ICM7216D INTERNAL CONTROL INTERNAL CONTROL 100Hz INPUT A INPUT CLOCK SELECTOR INPUT B REFERENCE COUNTER
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1
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10
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100
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1000 INTERNAL CONTROL RANGE SELECTOR INTERNAL CONTROL INTERNAL OR EXTERNAL ENABLE OSCILLATOR INPUT CLOCK SELECTOR INPUT A MAIN COUNTER FIGURE 11. SIMPLIFIED BLOCK DIAGRAM OF FUNCTIONS IMPLEMENTATION TABLE 2. 7216A/B INPUT ROUTING
ing long time intervals to give enough time for measurement completion. The resolution in this mode is the same as for
MAIN
period measurement. See the Time Interval Measurement
FUNCTION COUNTER REFERENCE COUNTER
section also. Frequency (fA) Input A 100Hz (Oscillator ÷105 or 104)
Unit Counter
- In this mode, the Main Counter is always Period (tA) Oscillator Input A enabled. The input A is counted by the Main Counter and Ratio (fA/fB) Input A Input B displayed continuously. Time Interval Oscillator Input A
Oscillator Frequency
- In this mode, the device makes a (A→B) Input B frequency measurement on its timebase. This is a self test Unit Counter Input A Not Applicable mode for device functionality check. For 10MHz timebase (Count A) the display will show 10000.0, 10000.00, 10000.000 and Osc. Freq. Oscillator 100Hz (Oscillator ÷105 or 104) Overflow in different ranges. (fOSC)
Range Input Frequency
- In this mode input A is counted by the Main The RANGE INPUT selects whether the measurement Counter for a precise period of time. This time is determined period is made for 1,10,100 or 1000 counts of the Reference by the time base oscillator and the selected range. For the Counter. As it is shown in Table 1, this gives different count- 10MHz (or 1MHz) time base, the resolutions are 100Hz, ing windows for frequency measurement and various cycles 10Hz, 1Hz and 0.1Hz. The decimal point on the display is for other modes of measurement. set for kHz reading. In all functional modes except Unit Counter, any change in
Period
- In this mode, the timebase oscillator is counted by the RANGE INPUT will stop the present measurement with- the Main Counter for the duration of 1,10,100 or 1000 (range out updating the display and then initiate a new measure- selected) periods of the signal at input A. A 10MHz timebase ment. This prevents an erroneous first reading after the gives resolutions of 0.1µs to 0.0001µs for 1000 periods aver- RANGE INPUT is changed. aging. Note that the maximum input frequency for period measurement is 2.5MHz.
Control Input Frequency Ratio
- In this mode, the input A is counted by Unlike the other multiplexed inputs, to which only one of the the Main Counter for the duration of 1,10,100 or 1000 (range digit outputs can be connected at a time, this input can be selected) periods of the signal at input B. The frequency at tied to different digit lines to select combination of controls. input A should be higher than input B for meaningful result. In this case, isolation diodes must be used in digit lines to The result in this case is unitless and its resolution can go up avoid crosstalk between them (see Figure 17). The direction to 3 digits after decimal point. of diodes depends on the device version, common anode or common cathode. For maximum noise immunity at this input,
Time Interval
- In this mode, the timebase oscillator is in addition to the 10K resistor which was mentioned before, counted by the Main Counter for the duration of a 1-0 transi- a 39pF to 100pF capacitor should also be placed between tion of input A until a 1-0 transition of input B. This means this input and the VDD or VSS (See Figure 17). input A starts the counting and input B stops it. If other ranges, except 0.01s/1 cycle are selected the sequence of
Display Off
- To disable the display drivers, it is necessary to input A and B transitions must happen 10,100 or 1000 times tie the D4 line to the CONTROL INPUT and have the HOLD until the display becomes updated; note this when measur- input at VDD. While in Display Off mode, the segments and 13-30