MC14490_13 Datasheet, PDF (4/11 Pages) ON Semiconductor – Hex Contact Bounce Eliminator

MC14490
SWITCHING CHARACTERISTICS (Note 3) (C_L = 50 pF, T_A = 25_C)
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Output Rise Time}
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ All Outputs
Characteristic
Symbol
t_TLH
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Output Fall Time}
Oscillator Output
t_THL
Debounce Outputs
t_THL
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Propagation Delay Time}
t_PHL
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Oscillator Input to Debounce Outputs
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _tPLH
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Clock Frequency (50% Duly Cycle)}
f_cl
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ (External Clock)
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Setup Time (See Figure 1)}
t_su
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Maximum External Clock Input}
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ Rise and Fall Time
Oscillator Input
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Oscillator Frequency}
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ OSC_out
C_ext ≥ 100 pF*
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{Note: These equations are intended to be a design guide.}
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ^{Laboratory experimentation may be required. Formulas are typically}
± 15% of actual frequencies.
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _{3. The formulas given are for the typical characteristics only at 25_C.}
t_r, t_f
f_osc, typ
V_DD
Typ
Vdc
Min (Note 4) Max
Unit
5.0
−
180
360
ns
10
−
90
180
15
−
65
130
5.0
−
100
200
ns
10
−
50
100
15
−
40
80
5.0
−
10
−
15
−
60
120
30
60
20
40
5.0
−
285
570
ns
10
−
120
240
15
−
95
190
5.0
−
370
740
10
−
160
320
15
−
120
240
5.0
−
2.8
1.4
MHz
10
−
6
3.0
15
−
9
4.5
5.0
100
50
−
ns
10
80
40
−
15
60
30
−
5.0
ns
10
No Limit
15
1.5
Hz
5.0
Cext (in mF)
10
4.5
Cext (in mF)
15
6.5
Cext (in mF)
4. 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 C_ext 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 = (V_DD − V_SS)  C_ext / (10 mA). For example, If V_DD − V_SS = 15
V and C_ext = 1 mF, the power supply must turn off no faster than t = (15 V)  (1 mF) / 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.
OSC_in
50%
V_DD
0V
t_PLH
A_out
50% ^90%
10%
t_r
t_PHL
A_out
90% _50%
10%
t_f
OSC_in
V_DD
50%
0V
t_su
A_in
50%
V_DD
0V
Figure 1. Switching Waveforms
D1
C_ext
D2
V_DD
V_DD
7
OSC_in
9
OSC_out
MC14490
Figure 2. Discharge Protection During Power Down
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