19-1122; Rev 1; 12/99
4 -P in µP Vo lt a g e Mo n it o rs w it h P in -S e le c t a b le
P o w e r-On Re s e t Tim e o u t De la y
Ge n e ra l De s c rip t io n
Fe a t u re s
The MAX821/MAX822 microprocessor (µP) supervisory
circuits monitor power supplies in µP and digital sys-
tems. They provide excellent circuit reliability and low
cost by eliminating external components and adjust-
ments when used with 5V-powered or 3V-powered cir-
cuits. The MAX821/MAX822 also provide a power-on
reset timeout delay that is pin selectable to 1ms (max),
20ms (min), or 100ms (min).
ꢀ Pin-Selectable, Precision Power-On Reset Delay:
1ms (max), 20ms (min), or 100ms (min)
ꢀ Precision Monitoring of +3V to +5V Power-Supply
Voltages
ꢀ 2.5µA Supply Current
ꢀ Guaranteed Over Temperature (-40°C to +125°C)
ꢀ Guaranteed RESET Valid to V
= 1V (MAX821)
CC
These devices perform a single function: they assert a
reset signal whenever the V
below a preset threshold, and they keep reset asserted
for the pin-selected reset timeout delay after V has
supply voltage falls
CC
ꢀ Power-Supply Transient Immunity
ꢀ No External Components
ꢀ SOT143 Package
CC
risen above the reset threshold. The only difference
between the two devices is that the MAX821 has an
active-low RESET output (which is guaranteed to be in
Ord e rin g In fo rm a t io n
the c orre c t s ta te for V
d own to 1V), while the
CC
PART
NOMINAL V (V)
TH
TOP MARK*
AZ_ _
MAX822 has an active-high RESET output. The reset
comparator is designed to ignore fast transients on
MAX821LUS-T
MAX821MUS-T
MAX821PUS-T
MAX821TUS-T
MAX821SUS-T
MAX821UUS-T
MAX821RUS-T
MAX822LUS-T
MAX822MUS-T
MAX822TUS-T
MAX822SUS-T
MAX822RUS-T
4.63
4.38
4.00
3.08
2.93
2.78
2.63
4.63
4.38
3.08
2.93
2.63
V
CC
. Reset thresholds suitable for operation with a vari-
BA_ _
BM_ _
BB_ _
BC_ _
BL_ _
ety of supply voltages are available.
Low supply current makes the MAX821/MAX822 ideal
for use in portable equipment. These devices come in a
4-pin SOT143 package.
BD_ _
BF_ _
________________________Ap p lic a t io n s
Bar-Code Scanners
BG_ _
BH_ _
BJ_ _
Computers
Controllers
BK_ _
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
* The first two letters in the package top mark identify the part,
while the remaining two letters are the lot-tracking code.
Note: These parts are offered in the SOT143-4 package, in the
extended temperature range (-40°C to +85°C).
__________Typ ic a l Op e ra t in g Circ u it
P in Co n fig u ra t io n
V
CC
V
CC
TOP VIEW
1
2
4
V
CC
GND
µP
MAX821
MAX822
MAX821
MAX822
RESET
INPUT
RESET
(RESET)
20ms
100ms
1ms
SRT
SRT
3
(RESET) RESET
GND
GND
SOT143
( ) ARE FOR MAX822
( ) ARE FOR MAX822
________________________________________________________________ Maxim Integrated Products
1
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