MC14490 查看數據表（PDF） - ON Semiconductor
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MC14490 Datasheet PDF : 12 Pages
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MC14490
SWITCHING CHARACTERISTICS (5.) (CL = 50 pF, TA = 25_C)
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Characteristic
VDD
Symbol
Vdc
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Output Rise Time
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ All Outputs
tTLH
5.0
10
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Output Fall Time
Oscillator Output
5.0
tTHL
10
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Debounce Outputs
tTHL
5.0
10
15
Propagation Delay Time
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Oscillator Input to Debounce Outputs
tPHL
5.0
10
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ tPLH
5.0
10
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ 15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Clock Frequency (50% Duly Cycle)
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ (External Clock)
fcl
5.0
10
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Setup Time (See Figure 1)
tsu
5.0
10
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Maximum External Clock Input
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Rise and Fall Time
Oscillator Input
tr, tf
5.0
10
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Oscillator Frequency
fosc, typ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ OSCout
5.0
Î ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Cext ≥ 100 pF*
10
Note: These equations are intended to be a design guide.
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Laboratory experimentation may be required. Formulas
15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ are typically ± 15% of actual frequencies.
Min
Typ (6.)
Max
Unit
—
180
360
ns
—
90
180
—
65
130
—
100
200
ns
—
50
100
—
40
80
—
60
120
—
30
60
—
20
40
—
285
570
ns
—
120
240
—
95
190
—
370
740
—
160
320
—
120
240
—
2.8
1.4
MHz
—
6
3.0
—
9
4.5
100
50
80
40
60
30
—
ns
—
—
ns
No Limit
1.5
Hz
Cext (in mF)
4.5
Cext (in mF)
6.5
Cext (in mF)
5. The formulas given are for the typical characteristics only at 25_C.
6. Data labelled “Typ” is not to be used for design purposes but is intended as an indication of the IC’s potential performance.
*POWER–DOWN CONSIDERATIONS
Large values of Cext may cause problems when powering down the MC14490 because of the amount of energy stored in the
capacitor. When a system containing this device is powered down, the capacitor may discharge through the input protection
diodes at Pin 7 or the parasitic diodes at Pin 9. Current through these internal diodes must be limited to 10 mA, therefore the
turn–off time of the power supply must not be faster than t = (VDD – VSS) Cext / (10 mA). For example, If VDD – VSS = 15
V and Cext = 1 µF, the power supply must turn off no faster than t = (15 V) (1 µF) / 10 mA = 1.5 ms. This is usually not a problem
because power supplies are heavily filtered and cannot discharge at this rate.
When a more rapid decrease of the power supply to zero volts occurs, the MC14490 may sustain damage. To avoid this
possibility, use external clamping diodes, D1 and D2, connected as shown in Figure 2.
OSCin
50%
VDD
0V
tPLH
Aout
50% 90%
10%
tr
D1
Cext
D2
VDD
VDD
tPHL
7
9
Aout
90% 50%
10%
OSCin OSCout
tf
OSCin
VDD
50%
0V
tsu
Ain
50%
VDD
0V
MC14490
Figure 1. Switching Waveforms
Figure 2. Discharge Protection During Power Down
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