3
www.fairchildsemi.com
F
FM809 Rev. A.1
General Description
The FM809 features a highly accurate voltage reference against
which the Vcc is compared. Once the Vcc is below the specified
threshold, it will drive the RESET line and continue to hold it low
until the V
CC
returns above the threshold and the time for the
RESET pulse duration has expired. The FM809 is immune to short
negative going transients on the V
line. The placement of a
0.1
μ
F bypass capacitor as close as possible to the V
CC
pin
provides additional transient immunity.
For a V
CC
value below 1.0V-1.3V, the FM809 does not sink current
on the RESET pin.
This is not a problem in most systems since most common devices
are not functional in this range. If it is desired for the FM809 reset
to be functional below the range above, it is suggested to use a
100K
pull-down resistor between RESET and V
SS
.
Interfacing to Bidirectional reset pins
FM809 can be used with microprocessors with bidirectional reset
pins. In order to allow the microprocessor to drive the reset line, the
output of the FM809 must be connected to the microprocessor
through a 4.7k
resistor. This will ensure that the RESET line has
correct level at both the FM809 as well as the device end.
Product Specifications
Absolute Maximum Ratings
Ambient Storage Temperature
All Input or Output Voltages
with Respect to Ground
Lead Temperature (Soldering, 10 seconds)
ESD Rating
Electrical Characteristics
–
65
°
C to +150
°
C
-0.3V to 6.5V
+300
°
C
2000V min.
Parameter
Symbol
Temp
Conditions
Min
Typ
Max
Units
V
CC
Range
Com
1.0
5.5V
V
I
ND
I
CC
1.2
5.5
V
Supply Current
Com
50
μ
A
100
μ
A
Reset Threshold
V
TH
Com
‘
L
’
Identifier
4.50
4.63
4.75
V
Ind
4.40
4.63
4.85
V
Com
‘
M
’
Identifier
4.25
4.38
4.50
V
Ind
4.16
4.38
4.56
V
Com
‘
J
’
Identifier
3.89
4.00
4.10
V
Ind
3.80
4.00
4.20
V
Com
‘
T
’
Identifier
3.00
3.08
3.15
V
Ind
2.92
3.08
3.23
V
Com
‘
S
’
Identifier
2.85
2.93
3.00
V
Ind
2.78
2.93
3.08
V
Com
‘
R
’
Identifier
2.55
2.63
2.70
V
Ind
2.50
2.63
2.75
V
nRESET Output Voltage High
V
OH
V
OL
T
RST
All
Isource = 150 mA
0.8V
CC
0.4
V
nRESET Output Voltage Low
All
Isink = 1.2mA
V
Reset Timeout Period
All
175
240
375
ms
Note:
Production testing done at TA = +25
°
C, over temperature limits guaranteed by design only.
Operating Conditions
Ambient Operating Temperature
Commercial
Industrial
0
°
C to +70
°
C
-40
°
C to +85
°
C