MAX821UUS-T [MAXIM]
4-Pin レP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay; 4引脚微处理器电压监视器具有引脚可选的上电复位超时周期
| 型号： | MAX821UUS-T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 4-Pin レP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay |
| 文件： | 总8页 (文件大小：79K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
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
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
Continuous Power Dissipation (T = +70°C)
A
V
......................................................................-0.3V to 6.0V
SOT143-4 (derate 4mW/°C above +70°C)...................320mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
CC
All Other Inputs.......................................-0.3V to (V + 0.3V)
Input Current, V , SRT......................................................20mA
Output Current, RESET or RESET.......................................20mA
CC
CC
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V = full range, T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.)
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
= 0°C to +70°C
MIN
1.0
TYP
MAX
5.5
UNITS
T
A
V
CC
Range
V
T
A
= -40°C to +85°C
1.2
5.5
T
= +25°C
2.5
7.0
A
MAX82_L/M/P,
= 5.5V, I
V
CC
= 0
= 0
OUT
T
A
= T
to T
12
MIN
MAX
Supply Current
I
CC
µA
T
A
= +25°C
1.8
5.5
MAX82_R/S/T/U,
= 5.5V, I
V
CC
OUT
T
A
= T
to T
9
MIN
MAX
T
= +25°C
4.56
4.50
4.31
4.25
3.97
3.91
3.04
3.00
2.89
2.85
2.74
2.70
2.59
2.55
4.63
4.38
4.00
3.08
2.93
2.78
2.63
4.70
4.75
4.45
4.50
4.04
4.09
3.11
3.15
2.96
3.00
2.81
2.85
2.66
2.70
A
MAX82_L
MAX82_M
MAX82_P
MAX82_T
MAX82_S
MAX82_U
MAX82_R
T
A
= -40°C to +125°C
= +25°C
T
A
T
A
= -40°C to +125°C
= +25°C
T
A
T
A
= -40°C to +125°C
= +25°C
T
A
Reset Threshold (Note 1)
V
TH
V
T
A
= -40°C to +125°C
= +25°C
T
A
T
A
= -40°C to +125°C
= +25°C
T
A
T
A
= -40°C to +125°C
= +25°C
T
A
T
A
= -40°C to +125°C
Reset Threshold Tempco
to Reset Delay (Note 1)
30
50
ppm/°C
µs
V
V
CC
falling at 1mV/µs
CC
SRT = GND
SRT = V
0.5
20
0.8
32
1
Reset Active Timeout Period
SRT Input Current (Note 2)
SRT Input Threshold
t
40
ms
µA
V
RP
CC
SRT = unconnected
100
-100
160
200
SRT = GND
RESET = low for MAX821,
RESET = high for MAX822
SRT = V
100
1
CC
SRT = unconnected
-1
V
0.07V
CC
IL
RESET = low for MAX821,
RESET = high for MAX822
V
0.9V
CC
IH
V
0.5V
CC
OPEN
2
_______________________________________________________________________________________
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
ELECTRICAL CHARACTERISTICS (continued)
(V = full range, T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.)
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SRT Input Capacitance
(Note 3) (see Setting
the Reset Timeout Delay
section)
Internal
20
pF
MAX821L/M/P only, I
= 3.2mA,
SINK
0.4
0.3
0.3
0.3
V
CC
= V
TH(MIN)
MAX821R/S/T/U only, I
= 1.2mA,
SINK
V
CC
= V
TH(MIN)
V
OL
T
A
= 0°C to +70°C,
V
CC
≥ 1V
RESET Output Voltage
(MAX821)
I
= 50µA
V
SINK
T
A
= -40°C to +85°C,
V
CC
≥ 1.2V
MAX821L/M/P only, I
= 800µA,
SOURCE
V
CC
-1.5
V
≥ V
TH(MAX)
CC
V
OH
MAX821R/S/T/U only, I
= 500µA,
SOURCE
0.8V
CC
V
CC
≥ V
TH(MAX)
MAX822L/M only, I
= 3.2mA,
SINK
0.4
0.3
V
CC
= VTH(MAX)
V
OL
RESET Output Voltage
(MAX822)
V
MAX822R/S/T only, I
= 1.2mA,
SINK
V
CC
= V
TH(MAX)
V
OH
I
= 150µA, 1.4V ≤ V ≤ V
0.8V
CC
SOURCE
CC
TH(MIN)
Note 1: RESET output for MAX821; RESET output for MAX822.
Note 2: During reset active timeout period only.
Note 3: Guaranteed by design.
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(T = +25°C, unless otherwise noted.)
A
RESET TIMEOUT PERIOD
vs. TEMPERATURE
RESET TIMEOUT PERIOD
vs. TEMPERATURE
RESET TIMEOUT PERIOD
vs. TEMPERATURE
1.0
36
35
34
33
180
175
170
165
SRT = UNCONNECTED
SRT = GND
SRT = V
CC
0.9
0.8
0.7
0.6
32
31
30
160
155
150
-40 -20
0
20
40 60
80 100
-40 -20
0
20
40 60
80 100
-40 -20
0
20
40 60
80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
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
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(T = +25°C, unless otherwise noted.)
A
MAX82_L/M POWER-DOWN RESET DELAY
vs. TEMPERATURE
MAX82_R/S/T POWER-DOWN RESET DELAY
vs. TEMPERATURE
60
50
40
30
45
40
35
30
25
20
15
10
5
V
FALLING AT 1mV/µs
CC
V
FALLING AT 1mV/µs
FALLING AT 10mV/µs
CC
20
10
0
V
CC
FALLING AT 10mV/µs
V
CC
0
-40 -20
0
20
40 60
80 100
-40 -20
0
20
40 60
80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
NORMALIZED SUPPLY
CURRENT vs. TEMPERATURE
1.003
1.10
1.002
1.001
1.000
1.05
1.00
0.95
0.90
0.999
0.998
0.997
-40 -20
0
20
40 60
80 100
-40 -20
0
20
40 60
80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
______________________________________________________________P in De s c rip t io n
PIN
NAME
FUNCTION
MAX821
MAX822
1
GND
Ground
1
Active-Low Reset Output. RESET is low while V is below the reset threshold. It remains
low for the reset timeout period after the reset condition is terminated. The reset timeout
period is determined by the SRT input.
CC
2
–
2
RESET
Active-High Reset Output. RESET is high while V is below the reset threshold. It remains
CC
high for the reset timeout period after the reset condition is terminated. The reset timeout
period is determined by the SRT input.
RESET
SRT
–
Set Reset Timeout Input. Connect to GND for 1ms (max) delay; connect to V for 20ms
CC
(min) delay; leave unconnected for 100ms (min) delay.
3
4
3
4
V
CC
Supply Voltage
4
_______________________________________________________________________________________
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
_______________De t a ile d De s c rip t io n
Re s e t Ou t p u t
300
T
A
= +25°C
A microprocessor’s (µP’s) reset input starts the µP in a
known state. These µP supervisory circuits assert reset
to prevent code-execution errors during power-up,
power-down, or brownout conditions. They also provide
a reset timeout delay that is pin programmable to 1ms
(max), 20ms (min), or 100ms (min). This feature allows
flexibility in designing bar-code scanners, hand-held
devices, and other applications that require quick or
nonstandard power-up times.
250
200
150
100
50
The MAX821’s RESET output is guaranteed to be a
logic low for V
> 1V. Once V
exceeds the reset
CC
CC
0
threshold, an internal timer keeps RESET low for the
reset timeout period, as determined by the Set Reset
Timeout (SRT) input. See the Setting the Reset Timeout
Delay section.
1
10
100
1000
RESET COMPARATOR OVERDRIVE, V -V (mV)
TH CC
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Comparator Overdrive
If a brownout condition occurs (V
reset threshold), RESET goes low. Any time V
below the reset threshold, the internal timer resets to
dips below the
CC
goes
CC
zero, and RESET goes low. The internal timer begins
__________Ap p lic a t io n s In fo rm a t io n
counting after V
returns above the reset threshold,
CC
and RESET remains low for the reset timeout period.
Ne g a t ive -Go in g V
Tra n s ie n t s
CC
While designed to issue a reset to the microprocessor
(µP) during power-up, power-down, and brownout con-
ditions, the MAX821/MAX822 are relatively immune to
The MAX822 has an active-high RESET output that is
the inverse of the MAX821’s RESET output.
short-duration, negative-going V transients (glitches).
S e t t in g t h e Re s e t Tim e o u t De la y
Use the three-level Set Reset Timeout (SRT) input to set
the reset timeout delay. Connect SRT to GND for a 1ms
CC
Figure 1 shows the maximum transient duration vs. reset
comparator overdrive for which the MAX821/MAX822
typically do not generate a reset pulse. This graph was
(max) delay; connect it to V
for a 20ms (min) delay;
CC
or leave it unconnected for a 100ms (min) delay.
generated using a negative-going pulse applied to V
,
CC
starting above the actual reset threshold and ending
below it by the magnitude indicated (reset comparator
overdrive). The graph indicates the typical maximum
If you choose to drive the SRT pin with an external sig-
nal, make sure the signal source can charge/discharge
the capacitance on SRT quickly enough (<500µs) to
avert an unintended reset timeout delay.
pulse width a negative-going V
transient may have
CC
without causing a reset pulse to be issued. As the mag-
nitude of the transient increases (goes farther below the
reset threshold), the maximum allowable pulse width
To ensure proper operation when selecting the 100ms
time out (SRT = unc onne c te d ), minimize c a p a c itive
loading on the SRT pin (< 200pF). Excessive capacitive
loading can select an unintended faster timeout mode.
decreases. Typically, for the MAX821/MAX822, a V
CC
transient that goes 100mV below the reset threshold and
lasts 12µs or less will not cause a reset pulse to be
issued. A 0.1µF capacitor mounted as close as possible
Re s e t Th re s h o ld Ac c u ra c y
The MAX821/MAX822 are designed to meet their worst-
case specifications over their entire operating tempera-
ture range. Choose a reset threshold guaranteed to
assert at a voltage below the power supply’s regulation
range and above the minimum specified operating volt-
age range for the system’s ICs.
to V
can provide additional transient immunity, if
CC
desired.
_______________________________________________________________________________________
5
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
En s u rin g a Va lid RESET Ou t p u t
V
CC
V
CC
Do w n t o V
= 0 V
CC
When V
falls below 1V, the MAX821 RESET output
CC
no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS logic inputs con-
nected to the RESET output can drift to undetermined
voltages. This presents no problem in most applica-
tions, since most µP and other circuitry is inoperative
V
V
CC
CC
R1
MAX822
MAX821
RESET
RESET
with V below 1V. However, in applications where the
CC
RESET output must be valid down to 0V, adding a pull-
down resistor to the RESET pin will cause any stray
leakage currents to flow to ground, holding RESET low
(Figure 2a). R1’s value is not critical; 100kΩ is large
enough not to load RESET, and small enough to pull
RESET to ground.
R1
GND
GND
b)
a)
Figure 2. RESET/RESET Valid to V = Ground Circuit
CC
A 100kΩ pull-up resistor to V
is also recommended
CC
for the MAX822 if RESET is required to remain valid for
< 1V (Figure 2b).
V
CC
BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
In t e rfa c in g t o µP s w it h
Bid ire c t io n a l Re s e t P in s
BUFFER
µPs with bidirectional reset pins (such as the Motorola
68HC11 series) can contend with the MAX821 reset
output. For example, if the MAX821 RESET output is
asserted high and the µP wants to pull it low, indetermi-
nate logic levels may result. To correct such cases,
connect a 4.7kΩ resistor between the MAX821 RESET
output and the µP reset I/O (Figure 3). Buffer the reset
output to other system components.
V
V
CC
CC
µP
MAX821
4.7k
RESET
RESET
GND
GND
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 492
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
6
_______________________________________________________________________________________
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
________________________________________________________P a c k a g e In fo rm a t io n
_______________________________________________________________________________________
7
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
NOTES
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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