si4021 Silicon Laboratories, si4021 Datasheet - Page 26

• Manufacturer Part Number: si4021
• Description: Si4021 Universal Ism Band Fsk Transmitter
• Manufacturer: Silicon Laboratories

Sensitive Reset Enabled, Ripple on V
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.
V
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
reset state. To avoid this phenomenon use adequate filtering on the power supply line to keep the level of the disturbing signal below
10mV
switching noise may be present on the V
and/or how to shift the switching frequency.
Related control commands
“PLL setting and Reset Mode Command”
“SW Reset Command”
dd
output
output
nRes
nRes
line filtering
dd
250mV
p-p
1.6V
line as smooth as possible. Noise or periodic disturbing signal superimposed the supply voltage may prevent the part getting out from
V
H
L
V
H
L
in the DC – 50kHz range for 200ms from V
dd
dd
Setting bit<1> to high will change the reset mode to normal from the default sensitive.
Issuing FE00h command will trigger software reset. See the Wake-up Timer Command.
Reset threshold voltage
Reset threshold voltage
(600mV)
(600mV)
dd
:
dd
line. Follow the manufacturer’s recommendations how to decrease the ripple of the regulator IC
dd
ramp start.. Typical example when a switch-mode regulator is used to supply the radio,
Reset ramp line
(100mV/ms)
Reset ramp line
(100mV/ms)
time
time
IA4221
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