Rainbow Electronics RF01 - Manual (Page 20)

RF01
Any negative change in the supply voltage will not cause reset event unless the V
dd
level reaches the reset
threshold voltage (250mV in normal mode, 1.6V in sensitive reset mode).
If the sensitive mode is disabled and the power supply turned off the V
dd
must drop below 250mV in order to
trigger a power-on reset event when the supply voltage is turned back on. If the decoupling capacitors keep
their charges for a long time it could happen that no reset will be generated upon power-up because the power
glitch detector circuit is disabled.
Note that the reset event reinitializes the internal registers, so the sensitive mode will be enabled again.
Sensitive Reset Enabled, Ripple on V
dd
:
Sensitive reset disabled:
Software reset
Software reset can be issued by sending the appropriate control command (described at the end of the section)
to the chip. The result of the command is the same as if power-on reset was occurred. When the nRES pin
connected to the reset pin of the microcontroller, using the software reset command may cause unexpected
problems.
V dd line filtering
During the reset event (caused by power-on, fast positive spike on the supply line or software reset command)
it is very important to keep the V
dd
line as smooth as possible. Noise or periodic disturbing signal superimposed
the supply voltage may prevent the part getting out from reset state. To avoid this phenomenon use adequate
filtering on the power supply line to keep the level of the disturbing signal below 10mV
p-p
in the DC – 50kHz
range for 200ms from V
dd
ramp start.. Typical example when a switch-mode regulator is used to supply the
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