mic6315-46d4uy Micrel Semiconductor, mic6315-46d4uy Datasheet - Page 5

• Manufacturer Part Number: mic6315-46d4uy
• Description: Mic6315 Open-drain ?p Reset Circuit
• Manufacturer: Micrel Semiconductor

Applications Information
Microprocessor Reset
The /RESET pin is asserted whenever V
reset threshold voltage or if /MR (manual reset) is forced
low. The /RESET pin remains asserted for the duration of
the reset timeout period after V
threshold or /MR has returned high. The reset function en-
sure the microprocessor is properly reset and powers up in
a known condition after a power failure. /RESET will remain
valid with V
The /RESET output is a simple open-drain N-channel MOS-
FET structure. A pull-up resistor must be used to pull this
output up to some voltage. For most applications, this volt-
age will be the same power supply that supplies V
MIC6315. It is possible, however, to tie this resistor to some
other voltage. This will allow the MIC6315 to monitor one
voltage while level-shifting the /RESET output to some other
voltage. The pull-up voltage must be limited to 6.0V or less
(absolute maximum) to avoid damage to the MIC6315. The
resistor must be small enough to supply current to the inputs
and leakage paths that are driven by the /RESET output.
/RESET Valid at Low Voltage
As V
pull the /RESET output low. At this point, the pull-up resistor
will pull the output high. The value of the pull-up resistor and
the voltage it is connected to will affect the point at which
this happens.
October 2005
CC
drops to 0V, the MIC6315 will no longer be able to
CC
as low as 1V.
CC
has risen above the reset
CC
falls below the
CC
to the
5
Wire OR'ing The /RESET Output
Because the RESET output is open-drain, several reset
sources can be wire-ORed, in parallel, to allow resets from
multiple sources.
V
The MIC6315 is relatively immune to negative-going V
glitches below the reset threshold. Typically, a negative-going
transient 125mV below the reset threshold with a duration of
20µs or less will not cause an unwanted reset. If additional
transient immunity is needed, a bypass capacitor can be
placed a close as possible to the MIC6315.
CC
Transients
MIC6315 Used in a Multiple Supply System
MR
MIC6315
+3.3V
V CC
RESET
10k
RESET
5V SYSTEM
+5.0V
V CC
M9999-102005
CC