MIC2776 Micrel Semiconductor, MIC2776 Datasheet - Page 5

• Manufacturer Part Number: MIC2776
• Description: Micro-Power Low Voltage Supervisor
• Manufacturer: Micrel Semiconductor

Functional Diagram
Functional Description
IN, Under-Voltage Detector Input
The voltage present at the IN pin is compared to the internal
300mV reference voltage. A reset is triggered if and when V
falls below V
the input voltage to be monitored such that V
V
trip-point. Hysteresis is employed to prevent chattering due to
noise.
RST, /RST Reset Output
Typically, the MIC2776 is used to monitor the power supply
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the reset output of a MIC2776 to the
reset input of a µC or µP, the processor will be properly reset
at power-on and during power-down and brown-out condi-
September 29, 2000
MIC2776
REF
as the voltage being monitored falls below the desired
REF
. Typically, a resistor divider is used to scale
GND
/MR
IN
* Pinout and polarity vary by device type.
See ordering information table.
V
DD
V
REF
I
PU
IN
will fall below
Delay
IN
5
tions. In addition, asserting /MR, the manual reset input, will
activate the reset function.
The reset outputs are asserted any time /MR is asserted or if
V
remain asserted for t
above the threshold boundary and /MR is released. A reset
pulse is also generated at power-on.
/MR, Manual Reset Input
The ability to initiate a reset via external logic or a manual
switch is provided in addition to the MIC2776’s automatic
supervisory functions. Driving the /MR input to a logic low
causes an immediate and unconditional reset to occur.
Assuming V
(returns high), the reset output will be de-asserted no less
than t
mechanical switch. Typically, a momentary push-button switch
is connected such that /MR is shorted to ground when the
switch contacts close. The switch may be connected directly
between /MR and GND. /MR has an internal 100nA pull-up
current to V
IN
One Shot
drops below the threshold voltage. The reset outputs
RST
later. /MR may be driven by a logic signal, or
DD
IN
and may be left open if unused.
R
S
is within tolerance when /MR is released
RST
Q
/Q
(min) after V
MIC2776
/RST*
RST*
IN
subsequently returns
MIC2776
Micrel