MAX825SEUK+T [MAXIM]
Power Supply Support Circuit, Fixed, 1 Channel, +2.93VV, BICMOS, PDSO5, ROHS COMPLIANT, MO-178AA, SOT-23, 5 PIN;
| 型号： | MAX825SEUK+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Support Circuit, Fixed, 1 Channel, +2.93VV, BICMOS, PDSO5, ROHS COMPLIANT, MO-178AA, SOT-23, 5 PIN 微处理器 监控 |
| 文件： | 总8页 (文件大小：80K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0487; Rev 1; 6/97
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
34/MAX825
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX823/MAX824/MAX825* microprocessor (µP)
supervisory circuits combine reset output, watchdog,
and manual-reset input functions in a 5-pin SOT23-5
package. They significantly improve system reliability
and accuracy compared to separate ICs or discrete
c omp one nts . The MAX823/MAX824/MAX825 a re
♦ Precision Monitoring of +3V, +3.3V, and +5V
Power Supplies
♦ Operating Current: 10µA (MAX823L/M)
3µA (MAX825T/S/R)
♦ Fully Specified Over Temperature
♦ 140ms Min Power-On Reset
specifically designed to ignore fast transients on V
.
CC
Five p re p rog ra mme d re s e t thre s hold volta g e s a re
a va ila b le , d e s ig na te d b y the following p a c ka g e
suffixes: L = 4.63V, M = 4.38V, T = 3.08V, S = 2.93V,
and R = 2.63V. All three devices have an active-low
reset output, which is guaranteed to be in the correct
♦ Guaranteed RESET Valid to V
= 1V
CC
♦ Power-Supply Transient Immunity
♦ Watchdog Timer with 1.6sec Timeout
(MAX823/MAX824)
state for V
down to 1V. The MAX824/MAX825 also
CC
♦ Manual-Reset Input (MAX823/MAX825)
♦ No External Components
have an active-high reset output. The following Selector
Guide explains the functions offered in this series of
parts.
______________Ord e rin g In fo rm a t io n
________________________Ap p lic a t io n s
†
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
5 SOT23-5
Battery-Powered Computers and Controllers
Embedded Controllers
Intelligent Instruments
MAX823_EUK
MAX824_EUK
MAX825_EUK
5 SOT23-5
Automotive Systems
5 SOT23-5
Critical µP Monitoring
Portable/Battery-Powered Equipment
†Insert the desired suffix letter (from the table below) into the
blank to complete the part number.
_____________________S e le c t o r Gu id e
RESET
SUFFIX
THRESHOLD (V)
FUNCTION
MAX823
MAX824
MAX825
L
M
T
4.63
4.38
3.08
2.93
2.63
✔
✔
✔
✔
—
✔
✔
Active-Low Reset
Active-High Reset
Watchdog Input
—
✔
✔
—
S
✔
Manual-Reset Input
R
Typical Operating Circuit appears at end of data sheet.
Marking Information appears at end of data sheet.
__________________________________________________________P in Co n fig u ra t io n s
TOP VIEW
1
2
3
5
4
V
1
2
3
5
4
1
2
3
5
4
RESET
GND
MR
RESET
GND
V
V
CC
RESET
GND
CC
CC
MAX823
MAX824
MAX825
WDI
RESET
WDI
MR
RESET
SOT23-5
SOT23-5
SOT23-5
*Patents Pending
________________________________________________________________ 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 408-737-7600 ext. 3468.
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.3V to +6.0V
Operating Temperature Range
All Other Pins ..............................................-0.3V to (V + 0.3V)
Input Current, All Pins Except RESET and RESET..............20mA
Output Current, RESET, RESET ..........................................20mA
MAX82_EUK .....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
CC
Rate of Rise, V ............................................................100V/µs
CC
Continuous Power Dissipation (T = +70°C)
A
SOT23-5 (derate 7.1mW/°C above +70°C)...................571mW
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
CC
= +4.75V to +5.5V for MAX82_L, V
= +4.5V to +5.5V for MAX82_M, V
= +3.15V to +3.6V for MAX82_T, V
= +3V
CC
CC
CC
to +3.6V for MAX82_S, V
= +2.7V to +3.6V for MAX82_R, T = T
to T , unless otherwise noted. Typical values are at
MAX
CC
A
MIN
T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
= 0°C to +70°C
MIN
1.0
TYP
MAX
UNITS
T
5.5
A
Operating Voltage Range
Supply Current
V
CC
V
T
A
= -40°C to +85°C
1.2
MAX823L/M,
MAX824L/M
10
5
24
12
WDI and MR
unconnected
MAX823T/S/R,
MAX824T/S/R
I
µA
SUPPLY
34/MAX825
MAX825L/M
4.5
3
12
MR unconnected
MAX82_L
MAX825T/S/R
8
T
A
= +25°C
4.56
4.50
4.31
4.25
3.04
3.00
2.89
2.85
2.59
2.55
4.63
4.70
4.75
4.45
4.50
3.11
3.15
2.96
3.00
2.66
2.70
T
= -40°C to +85°C
= +25°C
A
T
A
4.38
3.08
2.93
2.63
MAX82_M
MAX82_T
T
= -40°C to +85°C
= +25°C
A
T
A
Reset Threshold
V
RST
V
T
= -40°C to +85°C
= +25°C
A
T
A
MAX82_S
T
= -40°C to +85°C
= +25°C
A
T
A
MAX82_R
T
A
= -40°C to +85°C
MAX82_L/M
10
5
Reset Threshold Hysteresis
mV
ppm/°C
ms
MAX82_T/S/R
Reset Threshold Temperature
Coefficient
40
MAX82_L/M
140
140
200
200
280
280
Reset Timeout Period
t
RP
MAX82_T/S/R
2
_______________________________________________________________________________________
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
34/MAX825
ELECTRICAL CHARACTERISTICS (continued)
(V
= +4.75V to +5.5V for MAX82_L, V
= +4.5V to +5.5V for MAX82_M, V
= +3.15V to +3.6V for MAX82_T, V
= +3V
CC
CC
CC
CC
to +3.6V for MAX82_S, V
= +2.7V to +3.6V for MAX82_R, T = T
to T , unless otherwise noted. Typical values are at
MAX
CC
A
MIN
T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
- 1.5
TYP
MAX
UNITS
MAX82_L/M, V = V
max,
CC
RST
V
CC
I
= 120µA
SOURCE
V
OH
MAX82_T/S/R, V = V
max,
CC
RST
0.8V
CC
I
= 30µA
SOURCE
MAX82_L/M, V = V
min,
CC
RST
0.4
0.3
0.3
0.3
I
= 3.2mA
SINK
V
RESET Output Voltage
MAX82_T/S/R, V = V
min,
CC
RST
I
= 1.2mA
SINK
V
OL
T
A
= 0°C to +70°C, V = 1V,
CC
V
CC
falling, I
= 50µA
SINK
T
A
= -40°C to +85°C, V = 1.2V,
CC
V
CC
falling, V
= 0V, I
= 100µA
BATT
SINK
800
400
MAX82_L/M, RESET = 0V, V = 5.5V
CC
RESET Output Short-Circuit
Current (Note 2)
I
µA
SOURCE
MAX82_T/S/R, RESET = 0V, V = 3.6V
CC
V
OH
V
CC
> 1.8V, I
= 150µA
0.8V
CC
SOURCE
MAX824L/M, MAX825L/M,
= V max, I = 3.2mA
0.4
0.3
V
CC
RST
SINK
RESET Output Voltage
V
V
OL
MAX824T/S/R, MAX825T/S/R,
= V max, I = 1.2mA
V
CC
RST
SINK
V
RST
- V = 100mV
20
µs
V
CC
to RESET Delay
CC
WATCHDOG INPUT (MAX823/MAX824)
Watchdog Timeout Period
WDI Pulse Width
t
1.12
50
1.60
2.40
sec
ns
WD
t
V = 0.4V, V = 0.8V
IL IH CC
WDI
V
0.3V
CC
IL
WDI Input Threshold (Note 3)
WDI Input Current (Note 4)
V
= 5V
V
CC
V
IH
0.7V
CC
WDI = V , time average
CC
120
-15
160
µA
WDI = 0V, time average
-20
0.3V
MANUAL-RESET INPUT (MAX823/MAX825)
V
IL
CC
V
µs
ns
MR Input Threshold
MR Pulse Width
V
IH
0.7V
CC
1.0
MR Noise Immunity (pulse width
with no reset)
100
500
52
ns
MR to Reset Delay
35
75
kΩ
MR Pull-Up Resistance (internal)
Note 1: Over-temperature limits are guaranteed by design and not production tested.
Note 2: The RESET short-circuit current is the maximum pull-up current when RESET is driven low by a µP bidirectional reset pin.
Note 3: WDI is internally serviced within the watchdog period if WDI is left unconnected.
Note 4: The WDI input current is specified as the average input current when the WDI input is driven high or low. The WDI input is
designed to drive a three-stated-output device with a 10µA maximum leakage current and a maximum capacitive load of
200pF. This output device must be able to source and sink at least 200µA when active.
_______________________________________________________________________________________
3
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(MAX823L, V = +5V, T = +25°C, unless otherwise noted.)
CC
A
RESET TIMEOUT PERIOD
vs. TEMPERATURE
V
SUPPLY CURRENT
RESET COMPARATOR PROPAGATION DELAY
vs. TEMPERATURE
CC
vs. TEMPERATURE
250
240
12.5
12.0
30
V
CC
FALLING
25
20
15
10
5
230
220
210
200
190
180
11.5
11.0
10.5
10.0
9.5
9.0
170
160
150
8.5
8.0
7.5
0
-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)
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED RESET THRESHOLD
VOLTAGE vs. TEMPERATURE
MAXIMUM V TRANSIENT DURATION
CC
vs. RESET THRESHOLD OVERDRIVE
34/MAX825
2.0
1.9
1.06
1.04
1.02
1.00
0.98
0.96
0.94
160
140
120
100
80
1.8
1.7
1.6
1.5
1.4
1.3
RESET OCCURS
ABOVE CURVE
60
40
1.2
1.1
1.0
20
0
-40 -20
0
20
40
60
80 100
0
20
60
80
-40 -20
40
100
0
20 40 60 80 100 120 140 160 180 200
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV), V - V
RST
CC
4
_______________________________________________________________________________________
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
34/MAX825
______________________________________________________________P in De s c rip t io n
PIN
NAME
FUNCTION
MAX823
MAX824
MAX825
Active-Low Reset Output. Pulses low for 200ms when triggered, and remains
low whenever V is below the reset threshold or when MR is a logic low. It
CC
1
2
1
2
1
2
4
3
RESET
GND
remains low for 200ms after one of the following occurs: V rises above the
CC
reset threshold, the watchdog triggers a reset, or MR goes low to high.
Ground. 0V reference for all signals.
Manual-Reset Input. A logic low on MR asserts reset. Reset remains asserted as
long as MR is held low and for 200ms after MR returns high. The active-low input
has an internal 52kΩ pull-up resistor. It can be driven from a CMOS-logic line or
3
—
3
MR
shorted to ground with a switch. Leave open or connect to V if unused.
CC
—
RESET
Active-High Reset Output. Inverse of RESET.
Watchdog Input. If WDI remains either high or low for longer than the watch-
dog timeout period, the internal watchdog timer runs out and a reset is trig-
gered. The internal watchdog timer clears whenever reset is asserted, or
whenever WDI sees a rising or falling edge. If WDI is left unconnected or is
connected to a three-stated buffer output, the watchdog feature is disabled.
4
5
4
5
—
5
WDI
V
CC
Supply Voltage
V
CC
MAX823
MAX824
MAX825
RESET
RESET
GENERATOR
RESET
(MAX824/MAX825
ONLY)
V
CC
1.25V
MR
(MAX823/MAX825
ONLY)
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
WDI
(MAX823/MAX824
ONLY)
GND
Figure 1. Functional Diagram
_______________________________________________________________________________________
5
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
Wa t c h d o g In p u t (MAX8 2 3 /MAX8 2 4 )
In the MAX823/MAX824, the watchdog circuit monitors
the µP’s activity. If the µP does not toggle the watchdog
_______________De t a ile d De s c rip t io n
RES ET Ou t p u t
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX823/MAX824/MAX825 µP super-
visory circuits assert a reset to prevent code-execution
errors during power-up, power-down, and brownout
conditions. RESET is guaranteed to be a logic low for
input (WDI) within t
(1.6sec), reset asserts. The inter-
WD
nal 1.6sec timer is cleared by either a reset pulse or by
toggling WDI, which detects pulses as short as 50ns.
While reset is asserted, the timer remains cleared and
does not count. As soon as reset is released, the timer
starts counting (Figure 3).
V
CC
down to 1V. Once V
exceeds the reset thresh-
CC
old, an internal timer keeps RESET low for the specified
Disable the watchdog function by leaving WDI uncon-
nected or by three-stating the driver connected to WDI.
The watchdog input is internally driven low during the
first 7/8 of the watchdog timeout period and high for the
last 1/8 of the watchdog timeout period. When WDI is
left unconnected, this internal driver clears the 1.6sec
timer every 1.4sec. When WDI is three-stated or uncon-
ne c te d , the ma ximum a llowa b le le a ka g e c urre nt is
10µA and the maximum allowable load capacitance is
200pF.
reset timeout period (t ); after this interval, RESET
RP
returns high (Figure 2).
If a brownout condition occurs (V
dips below the
CC
reset threshold), RESET goes low. Each time RESET is
asserted it stays low for the reset timeout period. Any
time V
goes below the reset threshold the internal
CC
timer restarts. RESET both sources and sinks current.
RESET on the MAX824/MAX825 is the inve rs e of
RESET.
Ma n u a l-Re s e t In p u t (MAX8 2 3 /MAX8 2 5 )
Many µP-based products require manual-reset capabili-
ty, allowing the operator, a test technician, or external
log ic c irc uitry to initia te a re s e t. On the MAX823/
MAX825, a logic low on MR asserts reset. Reset remains
__________Ap p lic a t io n s In fo rm a t io n
Wa t c h d o g In p u t Cu rre n t
The MAX823/MAX824 WDI inputs are internally driven
through a buffer and series resistor from the watchdog
counter (Figure 1). When WDI is left unconnected, the
watchdog timer is serviced within the watchdog timeout
period by a low-high-low pulse from the counter chain.
For minimum watchdog input current (minimum overall
power consumption), leave WDI low for the majority of
the watchdog timeout period, pulsing it low-high-low
once within the first 7/8 of the watchdog timeout period
to reset the watchdog timer. If WDI is externally driven
high for the majority of the timeout period, up to 160µA
can flow into WDI.
34/MAX825
asserted while MR is low, and for t (200ms nominal)
RP
after it returns high. MR has an internal 52kΩ pull-up
resistor, so it can be left open if not used. This input can
be driven with CMOS-logic levels or with open-drain/
collector outputs. Connect a normally open momentary
switch from MR to GND to create a manual-reset func-
tion; external debounce circuitry is not required. If MR is
driven from long cables or the device is used in a noisy
environment, connect a 0.1µF capacitor from MR to
GND to provide additional noise immunity.
V
CC
V
CC
t
RST
V
V
RST
RST
1V
t
1V
RESET*
WDI
t
RP
t
RP
RD
RESET
t
t
RP
WD
t
RP
t
RD
RESET
GND
*RESET ON THE MAX824/MAX825 IS THE INVERSE OF RESET.
Figure 2. Reset Timing Diagram
Figure 3. MAX823/MAX824 Watchdog Timing Relationship
6
_______________________________________________________________________________________
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
34/MAX825
An optional 0.1µF bypass capacitor mounted close to
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
V
provides additional transient immunity.
CC
The RESET output maximum pull-up current is 800µA
for L/M versions (400µA for T/S/R versions). This allows
µPs with bidirectional resets, such as the 68HC11, to
force RESET low when the MAX823/MAX824/MAX825
are pulling RESET high (Figure 4).
Wa t c h d o g S o ft w a re Co n s id e ra t io n s
(MAX8 2 3 /MAX8 2 4 )
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
input at different points in the program, rather than
pulsing the watchdog input high-low-high or low-high-
low. This technique avoids a stuck loop, in which the
watchdog timer would continue to be reset inside the
loop, keeping the watchdog from timing out.
Ne g a t ive -Go in g V
Tra n s ie n t s
CC
The s e s up e rvis ors a re re la tive ly immune to s hort-
duration, negative-going V transients (glitches), which
CC
usually do not require the entire system to shut down.
Resets are issued to the µP during power-up, power-
down, and brownout conditions.
Figure 5 shows an example of a flow diagram where the
I/O driving the watchdog input is set high at the begin-
ning of the program, set low at the beginning of every
subroutine or loop, then set high again when the pro-
gram returns to the beginning. If the program should
hang in any subroutine, the problem would quickly be
corrected, since the I/O is continually set low and the
watchdog timer is allowed to time out, causing a reset
or interrupt to be issued. As described in the Watchdog
Input Current section, this scheme results in higher time
average WDI input current than does leaving WDI low
for the majority of the timeout period and periodically
pulsing it low-high-low.
The Typical Operating Characteristics show a graph of
the MAX823L’s Maximum V
Transient Duration vs.
CC
Reset Threshold Overdrive, for which reset pulses are
not generated. The graph was produced using nega-
tive-going V pulses, starting at 5V and ending below
CC
the reset threshold by the magnitude indicated (reset
threshold overdrive). The graph shows the maximum
pulse width that a negative-going V
transient can
CC
typically have without triggering a reset pulse. As the
amplitude of the transient increases (i.e., goes farther
below the reset threshold), the maximum allowable
pulse width decreases. Typically, a V
transient that
CC
goes 100mV below the reset threshold and lasts for
15µs or less will not trigger a reset pulse.
START
SET WDI
HIGH
V
CC
V
CC
MAX823
MAX824
MAX825
PROGRAM
CODE
V
CC
I
MAX = 800µA L, M
400µA T, S, R
SOURCE
RESET
GENERATOR
RESET
SUBROUTINE OR
PROGRAM LOOP
µP
SET WDI LOW
GND
GND
RETURN
Figure 4. Interfacing to µPs with Bidirectional Resets
Figure 5. Watchdog Flow Diagram
_______________________________________________________________________________________
7
5 -P in Mic ro p ro c e s s o r S u p e rvis o ry Circ u it s
__________Typ ic a l Op e ra t in g Circ u it
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 607
V
CC
V
CC
______________P a c k a g e In fo rm a t io n
V
CC
RESET
WDI
RESET
I/O
MARKING INFORMATION (TOP)
XXXX
MAX823
GND
µP
AAAI = MAX823L
AAAJ = MAX823M
AAAK = MAX823T
AAAL = MAX823S
AAAM = MAX823R
AAAN = MAX824L
AAAO = MAX824M
AAAP = MAX824T
AAAQ = MAX824S
AAAR = MAX824R
AAAS = MAX825L
AAAT = MAX825M
AAAU = MAX825T
AAAV = MAX825S
AAAW= MAX825R
MR
MANUAL
RESET
34/MAX825
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 -3 7 7 -7 6 0 0
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
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