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零件编号 | ZSCT1555D8 | ||
描述 | PRECISION SINGLE CELL TIMER | ||
制造商 | Zetex Semiconductors | ||
LOGO | |||
1 Page
PRECISION SINGLE CELL TIMER
ZSCT1555
ISSUE 2 - MAY 1998
DEVICE DESCRIPTION
These devices are precision timing circuits for
generation of accurate time delays or
oscillation. Advanced circuit design means that
these devices can operate from a single battery
cell with the minimum of quiescent current.
In monostable mode time delays are
controlled by a single resistor and capacitor
network. In astable mode the frequency and
duty cycle can be accurately and
independently controlled with two external
resistors and one capacitor.
The threshold and trigger levels are normally
set as a proportion of VCC by internal resistors.
These levels can be programmed by the use
of the control input pin.
When the trigger input reduces to a value
below the trigger level, the flip-flop is set and
the output goes high. With the trigger input
above the trigger level and the threshold input
above the threshold level, the flip-flop is reset
SCHEMATIC DIAGRAM
8
VCC
and the output goes low. The reset pin has
priority over all the other inputs and is used
to start new timing cycles. A low on the reset
input causes the flip-flop to reset forcing the
output low. Whenever the output is forced
low then the internal discharge transistor is
turned on.
FEATURES
• 0.9V supply operating voltage guaranteed
• Pin connections comparable with 555
series timers
• Very low quiescent current 74 µA
• SO8 and DIL8 packages
• Operating temperature range
compatible with battery technologies
APPLICATIONS
• Portable and battery powered
equipment
• Low voltage and low power systems
CONTROL
5
6
THRESH
2
TRIGGER
7
DISCHARGE
4
RESET
4-311
3
OUTPUT
1
GND
ZSCT1555
Figure 5 shows the monostable mode used as
a pulse width modulator. Here the trigger pin
is supplied with a continuous pulse train, the
resulting output pulse width is modulated by
a signal applied to the control pin.
Astable operation
The configuration of Figure 7 produces a free
running multivibrator circuit whose frequency
is independent of supply voltage. The ratio of
resistors RA and RB precisely sets the circuit
duty cycle. The capacitor is charged and
discharged between thresholds at 0.2VCC and
0.8VCC. Oscillation frequency (f) and duty cycle
(d) can be calculated using the following
equations:-
f = 0.62/(RA + 2RB)CT
d = RB /(RA + 2RB)
Figure 5
Figure 6 shows typical waveform examples.
Figure 7
Figure 8 shows the waveforms generated in
this mode of operation.
Figure 6
Figure 8
4-318
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页数 | 10 页 | ||
下载 | [ ZSCT1555D8.PDF 数据手册 ] |
零件编号 | 描述 | 制造商 |
ZSCT1555D8 | PRECISION SINGLE CELL TIMER | Zetex Semiconductors |
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