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8.0
4.0
0
–4.0
–8.0
–12
R TC = 56 kΩ,
R S = 0, f = 10.15 kHz @ V DD = 10 V, T A = 25 C
{
C = 1000 pF
R S = 120 kΩ, f = 7.8 kHz @ V DD = 10 V, T A = 25 C
–16
–55
–25
0
T A , AMBIENT TEMPERATURE ( C), DEVICE ONLY
Figure 5. RC Oscillator Stability
R S
R TC
C
Figure 7. RC Oscillator Circuit
Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î
Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î Î
A test function (see Figure 8) has been
included for the reduction of test time required to
included for the reduction of test time required to
exercise all 24 counter stages. This test function
divides the counter into three 8–stage sections,
and 255 counts are loaded in each of the
8–stage sections in parallel. All flip–flops are
now at a logic "1". The counter is now returned
g
to the normal 24–stages in series configuration.
One more pulse is entered into Input 2 (In 2)
which will cause the counter to ripple from an all
"1" state to an all "0" state.
MOTOROLA CMOS LOGIC DATA
TEST CIRCUIT
V DD = 15 V
FIGURE 7
10 V
5.0 V
25
50
75
100
V DD
V DD
V DD
IN 1
OUT 1
OUT 2
Q18
Q19
IN 2
Q20
Q21
Q22
Q23
R
Q24
V SS
V SS
FUNCTIONAL TEST SEQUENCE
Inputs
Reset
In 2
1
0
100
50
20
10
5.0
f AS A FUNCTION
OF C
2.0
(R TC = 56 kΩ)
(R S = 120 k)
1.0
0.5
0.2
0.1
1.0 k
125
0.0001
Figure 6. RC Oscillator Frequency as a
PULSE
GENERATOR
Figure 8. Functional Test Circuit
Outputs
Out 2
V SS
V DD
Q18 thru Q24
V DD
Gnd
0
0
1
1
0
0
1
1
—
—
—
—
—
—
1
1
0
0
0
0
Gnd
Gnd
V DD
1
0
1
0
0
1
TEST CIRCUIT
V DD = 10 V
FIGURE 7
f AS A FUNCTION
OF R TC
(C = 1000 pF)
(R S 2R TC )
10 k
100 k
R TC , RESISTANCE (OHMS)
0.001
0.01
C, CAPACITANCE (µF)
Function of R TC and C
V DD
V DD
IN 1
Q18
Q19
Q20
Q21
IN 2
Q22
Q23
Q24
OUT 1
R
OUT 2
V SS
V SS
Comments
Counter is in three 8–stage
sections in parallel mode
Counter is reset In 2 and
Counter is reset. In 2 and
0
Out 2 are connected
together
First "0" to "1" transition
on In 2, Out 2 node.
255 "0" to "1" transitions
are clocked into this In 2,
Out 2 node.
The 255th "0" to "1"
1
transition.
1
1
Counter converted back to
1
24–stages in series mode.
Out 2 converts back to an
1
output.
Counter ripples from an all
0
"1" state to an all "0" stage.
MC14521B
1.0 m
0.1
6–305
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