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Número de pieza | FM1233AD | |
Descripción | 3-Pin C Supervisor Circuit | |
Fabricantes | Fairchild Semiconductor | |
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Hay una vista previa y un enlace de descarga de FM1233AD (archivo pdf) en la parte inferior de esta página. Total 7 Páginas | ||
No Preview Available ! September 2004
FM1233A
3-Pin µC Supervisor Circuit
General Description
The FM1233A is a supervisor circuit that monitors a micropro-
cessor power supply or other system voltage and issues a reset
pulse when a fault condition exists. Several different threshold
voltages are offered to accommodate 3.3V and 3.0V systems
with different tolerances.
FM1233A features a precision temperature-compensated volt-
age reference and comparator. When VCC falls to the threshold
voltage, a RESET pulse is issued, holding the output in the
active state. When power rises above VTH, the reset remains
asserted for a minimum period (tRST) to allow the system clock
and other circuits to stabilize. The reset output of FM1233A is of
open-drain active low type.
The FM1233A also can monitor a switch closure on its output,
enabling it to recognize an external reset from a pushbutton
switch or a µP. In the case of a switch, the closure will be
debounced by circuitry internal to the FM1233A.
Features
■ Precision monitoring of 3.3V and lower voltage
microprocessor systems
■ VTH values of 3.08V, 2.88V and 2.72V
■ Automatic restart of microprocessor after power failure
■ Reset Timeout Period Choice:
– Options AC and AD: 140ms (min)/256ms (typ)
– Option ABA: 17ms (min)/32ms (typ)
– Available on request: 64ms (typ) and 128ms (typ)
■ Internal 5kΩ pull-up resistor
■ Operating Temperature -40°C to +105°C
■ Monitors external pushbutton override
■ Internal switch debounce circuitry
■ SOT23-3 package
Typical Operating Circuit
VCC
GND
Connection Diagram
3
FM1233A
12
RESET
Controller
GND 1
FM1233A 3 VCC
RESET 2
SOT23-3 Package
©2004 Fairchild Semiconductor Corporation
FM1233A Rev. E
1
www.fairchildsemi.com
1 page General Description
The FM1233A features a highly accurate voltage reference to
which VCC is compared. Once VCC is below the specified thresh-
old, it will drive the RESET line and continue to hold it low until
VCC returns above the threshold and the time for the RESET
pulse duration has expired. The FM1233A is immune to short
negative going transients on the VCC line. The placement of a
0.1µF bypass capacitor as close as possible to the VCC pin pro-
vides additional transient immunity.
For a VCC value below 1.0V, the FM1233A does not sink very
much current on the RESET pin. This is not a problem in most
systems since common devices are not functional in this range.
If it is desired for the FM1233A reset to be functional below this
range, use a 100KΩ pull-down resistor between RESET and
VSS.
Bi-Directional Reset
The FM1233A permits a pushbutton (or a signal) to initiate a
reset externally. Once this external reset is detected on the
reset pin, FM1233 also actively asserts the reset signal to main-
tain the Reset Timeout period when the external reset is not
present .
FM1233 internally debounces glitches seen during a typical
push button closure. For proper operation, the external switch
should be paralleled by an external capacitor of 100pF to
0.01µF.
Connecting an External Reset to the FM1233A
VCC
3
FM1233
Controller
GND
12
RESET
PUSH
BUTTON
100pF
FM1233A Rev. E
5 www.fairchildsemi.com
5 Page |
Páginas | Total 7 Páginas | |
PDF Descargar | [ Datasheet FM1233AD.PDF ] |
Número de pieza | Descripción | Fabricantes |
FM1233A | 3-Pin C Supervisor Circuit | Fairchild Semiconductor |
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FM1233AC | 3-Pin C Supervisor Circuit | Fairchild Semiconductor |
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