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SA56614-XX Datasheet, PDF (8/14 Pages) NXP Semiconductors – CMOS system reset
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Philips Semiconductors
CMOS system reset
Product data
SA56614-XX
TIMING DIAGRAM
The timing diagram shown in Figure 13 depicts the operation of the
device. Letters A-J on the TIME axis indicate specific events.
A: At ‘A’, VDD begins to increase. Also the VOUT voltage initially
increases but abruptly decreases when VDD reaches the level
(approximately 0.8 V) that activates the internal bias circuitry and
RESET is asserted.
B: At ‘B’, VDD reaches the threshold level of VSH. At this point the
device releases the hold on the VOUT reset. The Reset output VOUT
tracks VDD as it rises above VSH (assuming the reset pull-up resistor
RPU is connected to VDD). In a microprocessor based system these
events release the reset from the microprocessor, allowing the
microprocessor to function normally.
C-D: At ‘C’, VDD begins to fall, causing VOUT to follow. VDD
continues to fall until the VSL undervoltage detection threshold is
reached at ‘D’. This causes a reset signal to be generated (VOUT
Reset goes LOW).
D-E: Between ‘D’ and ‘E’, VDD starts rising.
E: At ‘E’, VDD rises to the VSH. Once again, the device releases
the hold on the VOUT reset. The Reset output VOUT tracks VDD as it
rises above VSH.
F-G: At ‘F’, VDD is above the upper threshold and begins to fall,
causing VOUT to follow it. As long as VDD remains above the VSH,
no reset signal will be triggered. Before VDD falls to the VSH, it
begins to rise, causing VOUT to follow it. At ‘G’, VDD returns to
normal.
H: At event ‘H’ VDD falls until the VSL undervoltage detection
threshold point is reached. At this level, a RESET signal is
generated and VOUT goes LOW.
J: At ‘J’ the VDD voltage has decreased until normal internal circuit
bias is unable to maintain a VOUT reset. As a result, VDD may rise to
less than 0.8 V. As VDD decreases further, VOUT reset also
decreases to zero.
VSH
VSL
VDD
0
∆VS
VOUT
0
A
B
CD
E
F
G
TIME
Figure 13. Timing diagram.
H
J
SL01354
2001 Jun 19
8
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