MAX821 Datasheet, PDF (1/8 Pages) Maxim Integrated Products – 4-Pin μP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay

19-1122; Rev 1; 12/99
4-Pin µP Voltage Monitors with Pin-Selectable
Power-On Reset Timeout Delay
General Description
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).
These devices perform a single function: they assert a
reset signal whenever the V_CC supply voltage falls
below a preset threshold, and they keep reset asserted
for the pin-selected reset timeout delay after V_CC has
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
the correct state for V_CC down to 1V), while the
MAX822 has an active-high RESET output. The reset
comparator is designed to ignore fast transients on
V_CC. Reset thresholds suitable for operation with a vari-
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.
________________________Applications
Bar-Code Scanners
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
__________Typical Operating Circuit
Features
o Pin-Selectable, Precision Power-On Reset Delay:
1ms (max), 20ms (min), or 100ms (min)
o Precision Monitoring of +3V to +5V Power-Supply
Voltages
o 2.5µA Supply Current
o Guaranteed Over Temperature (-40°C to +125°C)
o Guaranteed RESET Valid to V_CC = 1V (MAX821)
o Power-Supply Transient Immunity
o No External Components
o SOT143 Package
Ordering Information
PART
NOMINAL V_TH (V)
TOP MARK*
MAX821LUS-T
4.63
AZ_ _
MAX821MUS-T
4.38
BA_ _
MAX821PUS-T
4.00
BM_ _
MAX821TUS-T
3.08
BB_ _
MAX821SUS-T
2.93
BC_ _
MAX821UUS-T
2.78
BL_ _
MAX821RUS-T
2.63
BD_ _
MAX822LUS-T
4.63
BF_ _
MAX822MUS-T
4.38
BG_ _
MAX822TUS-T
3.08
BH_ _
MAX822SUS-T
2.93
BJ_ _
MAX822RUS-T
2.63
BK_ _
* 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).
20ms
100ms
1ms
V_CC
MAX821
MAX822
RESET
SRT
(RESET)
GND
V_CC
µP
RESET
INPUT
GND
( ) ARE FOR MAX822
Pin Configuration
TOP VIEW
GND ¹
MAX821
MAX822
4 V_CC
(RESET) RESET ²
3 SRT
( ) ARE FOR MAX822
SOT143
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