IMP811JEUS-T IMP [IMP, Inc], IMP811JEUS-T Datasheet - Page 6

• Manufacturer Part Number: IMP811JEUS-T
• Description: 4-pin ?P Voltage Supervisor with Manual Reset
• Manufacturer: IMP [IMP, Inc]

6
RESET Output Operation
In µP/µC systems it is important to have the processor begin
operation from a known state or be able to return the system to a
known state. A RESET output to a processor is provided to pre-
vent improper operation during power supply sequencing or low
voltage – brownout – conditions.
The IMP811/812 are designed to monitor the system power sup-
ply voltages and issue a RESET signal when levels are out of
range. RESET outputs are guaranteed to be active for V
1.1V. When V
keeps RESET active for the reset timeout period, after which
RESET becomes inactive (HIGH for the IMP811 and LOW for the
IMP812).
Valid Reset with V
To ensure that logic inputs connected to the IMP811 RESET pin
are in a known state when V
resistor at RESET is needed. The value is not critical.
A similar pull-up resistor to V
Application Information
Supply
Power
Figure 2. RESET Valid with V
CC
exceeds the reset threshold, an internal timer
CC
under 1.1V
CC
MR
CC
is under 1.1V, a 100kΩ pull-down
IMP811
is needed with the IMP812.
V CC
GND
RESET
CC
Under 1.1V
811/12_04.eps
408-432-9100/www.impweb.com
100k
CC
9
above
If V
becomes active. Alternatively, external circuitry or a human oper-
ator can initiate this condition using the Manual Reset (MR) pin.
There is an internal pullup on MR so it can be left open if it is not
used. MR can be driven by TTL/CMOS logic or even an external
switch, since it is already debounced. If the switch is at the end of
a long cable, it might require a bypass (100nF) at the pin if noise
pickup is a problem.
Six voltage thresholds are available to support 3V and 5V systems:
Negative V
Typically short duration transients of 100mV amplitude and 20µs
duration do not cause a false RESET. A 0.1µF capacitor at V
increases transient immunity.
CC
Supply
Power
drops below the reset threshold, RESET automatically
Figure 3. RESET Valid with V
CC
M
S
R
Transients
L
J
T
MR
IMP8
IMP8
IMP812
GND
V CC
RESET
1
1
CC
1
1
Under 1.1V
4.63
4.38
4.00
3.08
2.93
2.63
, IMP8
, IMP8
811/12_05.eps
©
100kΩ
1999 IMP, Inc.
1
1
2
2
CC