MAX1232CSA+TG126 [MAXIM]
Power Supply Support Circuit,;
| 型号： | MAX1232CSA+TG126 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Support Circuit, |
| 文件： | 总6页 (文件大小：510K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3899; Rev 1; 11/05
Microprocessor Monitor
MAX132
General Description
Features
o Consumes 1/10th the Power of the DS1232
The MAX1232 microprocessor (µP) supervisory circuit
provides µP housekeeping and power-supply supervi-
sion functions while consuming only 1/10th the power of
the DS1232. The MAX1232 enhances circuit reliability
in µP systems by monitoring the power supply, monitor-
ing the software execution, and providing a debounced
manual reset input. The MAX1232 is a plug-in upgrade
of the Dallas DS1232.
o Precision Voltage Monitor—Adjustable +4.5V
or +4.75V
o Power-OK/Reset Pulse Width—250ms Min
o No External Components
o Adjustable Watchdog Timer—150ms, 600ms,
or 1.2s
A reset pulse of at least 250ms duration is supplied on
power-up, power-down, and low-voltage brownout
conditions (5% or 10% supply tolerances can be
selected digitally). Also featured is a debounced man-
ual reset input that forces the reset outputs to their
active states for a minimum of 250ms. A digitally pro-
grammable watchdog timer monitors software execu-
tion and can be programmed for timeout settings of
150ms, 600ms, or 1.2s. The MAX1232 requires no
external components.
o Debounced Manual Reset Input for External
Override
o Available in 8-Pin PDIP/SO and 16-Pin Wide SO
Packages
Ordering Information
PART
MAX1232C/D
MAX1232CPA
MAX1232CSA
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
Dice*
8 PDIP
8 SO
Applications
Ordering Information continued on last page.
*Contact factory for dice specifications.
Computers
Devices in PDIP and SO packages are available in both leaded
and lead-free packaging. Specify lead free by adding the +
symbol at the end of the part number when ordering. Lead free
not available for CERDIP package.
Controllers
Intelligent Instruments
Automotive Systems
Critical µP Power Monitoring
Pin Configurations
TOP VIEW
PB RST
TD
1
2
3
4
8
7
6
5
V
CC
ST
Typical Operating Circuit
MAX1232
TOL
RST
RST
GND
RST
V
CC
5%/10%
TOLERANCE
SELECT
DIP/SO
RESET
GENERATOR
TOL
N.C.
REF
1
2
3
4
5
6
7
8
16 N.C.
15
RST
PB RST
N.C.
TD
V
CC
MAX1232
PB RST
14 N.C.
13 ST
DEBOUNCE
MAX1232
N.C.
TOL
12 N.C.
11 RST
10 N.C.
WATCHDOG
TIMEBASE
SELECT
TD
ST
WATCHDOG
TIMER
N.C.
GND
GND
9
RST
WIDE SO
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Microprocessor Monitor
ABSOLUTE MAXIMUM RATINGS
Voltage on Any Pin (with respect to GND)……………-1V to +7V
Operating Temperature Range
Storage Temperature Range……………………-65°C to +160°C
Lead Temperature (soldering, 10s)………………………+300°C
C Suffix………………………………………………0°C to +70°C
E Suffix.……………………………………………-40°C to +85°C
M Suffix .…………………………………………-55°C to +125°C
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.
MAX132
Recommended DC Operating Conditions
(T = T
A
to T
)
MAX
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
V
4.5
5.0
5.5
V
CC
ST and PBRST Input High Level
(Note 1)
V
+
CC
0.3
V
2.0
V
V
IH
ST and PBRST Input Low Level
V
-0.3
+0.8
IL
DC Electrical Characteristics
(V
= +4.5V to +5.5V, T = T
A
to T
)
MAX
CC
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
-1.0
-1.0
2.0
TYP
MAX
UNITS
µA
Input Leakage ST, TOL
Output Current RST
I
+1.0
IL
I
V
V
= 2.4V
= 0.4V
-12
10
mA
mA
µA
OH
OH
OL
Output Current RST, RST
Operating Current (Note 2)
I
OL
CC
I
50
200
4.74
4.49
V
V
5% Trip Point (Note 3)
10% Trip Point (Note 3)
V
V
TOL = GND
TOL = V
4.50
4.25
4.62
4.37
V
CC
CC
CCTP
CCTP
V
CC
Capacitance (Note 4)
(T = +25°C)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
pF
Input Capacitance ST, TOL
C
5
7
IN
Output Capacitance RST, RST
C
pF
OUT
2
_______________________________________________________________________________________
Microprocessor Monitor
MAX132
AC Electrical Characteristics
(V
= +5V 10%, T = T
A
to T
)
MAX
CC
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
20
TYP
MAX
UNITS
ms
PBRST (Note 5)
PBRST Delay
t
Figure 3
Figure 3
PB
t
1
4
20
ms
PBD
Reset Active Time
ST Pulse Width
t
250
75
610
1000
ms
RST
t
Figure 4
ns
ST
Figure 4, TD pin = 0V
TD pin = open
62.5
250
500
10
150
600
250
1000
2000
ST Timeout Period
t
ms
TD
TD pin = V
Figure 5
1200
CC
V
V
Fall Time (Note 4)
Rise Time (Note 4)
t
µs
µs
CC
CC
F
t
Figure 6
0
B
V
Low
Detect to RST High and RST
CC
t
t
Figure 7, V
Figure 8, V
falling
rising
100
ns
BPD
BPU
CC
CC
V
Detect to RST Low and RST
CC
250
610
1000
ms
Open (Note 6)
Note 1: PBRST is internally pulled up to V
Note 2: Measured with outputs open.
Note 3: All voltages referenced to GND.
Note 4: Guaranteed by desing.
with an internal impedance of typically 40kΩ.
CC
Note 5: PBRST must be held low for a minimum of 20ms to guarantee a reset.
Note 6: t = 5µs.
R
Pin Description
PIN
NAME
FUNCTION
WIDE SO
DIP/SO
1, 3, 5, 7, 10,
12, 14, 16
—
N.C.
PBRST
TD
No Connection
Pushbutton Reset Input. A debounced active-low input that ignores pulses less than 1ms
in duration and is guaranteed to recognize inputs of 20ms or greater.
2
4
1
2
Time Delay Set. The watchdog timebase select input (t = 150ms for TD = 0V, t
600ms for TD = open, t = 1.2s for TD = V ).
=
TD
TD
TD
CC
6
8
3
4
TOL
Tolerance Input. Connect to GND for 5% tolerance or to V
Ground
for 10% tolerance.
CC
GND
Reset Output (Active High). Goes active:
(1) If VCC falls below the selected reset voltage threshold
(2) If PBRST is forced low
9
5
RST
(3) If ST is not strobed within the minimum timeout period
(4) During power-up
11
13
15
6
7
8
RST
ST
Reset Output (Active Low, Open-Drain). See RST.
Strobe Input. Input for watchdog timer.
The +5V Power-Supply Input
V
CC
_______________________________________________________________________________________
3
Microprocessor Monitor
Watchdog Timer
The microprocessor drives the ST input with an
input/output (I/O) line. The microprocessor must toggle
the ST input within a set period (as determined by TD)
to verify proper software execution. If a hardware or
software failure keeps ST from toggling within the mini-
mum timeout period—ST is activated only by falling
edges (a high-to-low transition)—the MAX1232 reset
outputs are forced to their active states for 250ms
(Figure 2). This typically initiates the microprocessor’s
power-up routine. If the interruption continues, new
reset pulses are generated each timeout period until ST
is strobed. The timeout period is determined by the TD
input connection. This timeout period is typically 150ms
with TD connected to GND, 600ms with TD floating, or
Detailed Description
Power Monitor
A voltage detector monitors V
and holds the reset
CC
outputs (RST and RST) in their active states whenever
V
is below the selected 5% or 10% tolerance (4.62V
CC
or 4.37V, typically). To select the 5% level, connect
TOL to ground. To select the 10% level, connect TOL to
V
CC
. The reset outputs will remain in their active states
MAX132
until V
has been continuously in-tolerance for a mini-
CC
mum of 250ms (the reset active time) to allow the
power supply and µP to stabilize.
The RST output both sinks and sources current, while
the RST output, an open-drain MOSFET, sinks current
only and must be pulled high.
1200ms with TD connected to V
.
CC
Pushbutton Reset Input
The MAX1232’s debounced manual reset input
(PBRST) manually forces the reset outputs into their
active states. The reset outputs go active after PBRST
The software routine that strobes ST is critical. The
code must be in a section of software that executes fre-
quently enough so the time between toggles is less
than the watchdog timeout period. One common tech-
nique controls the microprocessor I/O line from two
sections of the program. The software might set the I/O
line high while operating in the foreground mode, and
set it low while in the background or interrupt mode. If
both modes do not execute correctly, the watchdog
timer issues reset pulses.
has been held low for a time t
, the pushbutton reset
PBD
delay time. The reset outputs remain in their active
states for a minimum of 250ms after PBRST rises above
V
IH
(Figure 3).
A mechanical pushbutton or an active logic signal can
drive the PBRST input. The debounced input ignores
input pulses less than 1ms and is guaranteed to recog-
nize pulses of 20ms or greater. The PBRST input has
an internal pullup to V
of about 100µA; therefore, an
CC
external pullup resistor is not necessary.
+5V
+5V
10kΩ
V
TD
ST
CC
7805
3-TERMINAL
REGULATOR
+8V
+5V
V
RST
ST
RESET
I/O
PB RST
MAX1232
CC
MICROPROCESSOR
RESET
MICROPROCESSOR
0.1µF
MAX1232
RST
I/O
TD
TOL GND
GND TOL
Figure 1. Pushbutton Reset
Figure 2. Watchdog Timer
4
_______________________________________________________________________________________
Microprocessor Monitor
MAX132
t
ST
ST
t
PB
t
PBD
PB RST
t
TD
V
IH
V
IL
NOTE: t IS THE MAXIMUM ELAPSED TIME BETWEEN ST HIGH-TO-LOW
SD
TRANSITIONS (ST IS ACTIVATED BY FALLING EDGES ONLY) WHICH WILL
KEEP THE WATCHDOG TIMER FROM FORCING THE RESET OUTPUTS
t
RST
ACTIVE FOR A TIME OF t . t IS A FUNCTION OF THE VOLTAGE AT
RST TD
THE TD PIN, AS TABULATED BELOW.
RST
RST
t
TD
TYP
CONDITION
MIN
MAX
62.5ms
250ms
500ms
250ms
1000ms
2000ms
TD pin = 0V
TD pin = open
150ms
250ms
1200ms
TD pin = V
CC
Figure 3. Pushbutton Reset. The debounced PBRST input
ignores input pulses less than 1ms and is guaranteed to rec-
ognize pulses of 20ms or greater.
Figure 4. Watchdog Strobe Input
t
F
t
R
V
CC
+4.75V
+4.75V
+4.25V
+4.25V
V
CC
Figure 5. Power-Down Slew Rate
Figure 6. Power-Up Slew Rate
_______________________________________________________________________________________
5
Microprocessor Monitor
V
CC
+4.5V (5% TRIP POINT)
+4.75V (5% TRIP POINT)
+4.5V (10% TRIP POINT)
+4.25V (10% TRIP POINT)
V
CC
MAX132
t
t
RPD
RPU
RST
RST
RST
RST
V
V
OH
OH
V
V
OL
OL
V
SLEW RATE = 1.66mV/µsec (0.5V/300µsec)
CC
Figure 7. VCC Detect Reset Output Delay (Power-Down)
Figure 8. VCC Detect Reset Output Delay (Power-Up)
Chip Topography
Ordering Information (continued)
PART
TEMP RANGE
PIN-PACKAGE
16 Wide SO
8 PDIP
PB RST
V
CC
MAX1232CWE
MAX1232EPA
MAX1232ESA
MAX1232EWE
MAX1232MJA
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
8 SO
16 Wide SO
8 CERDIP
Ordering Information continued on last page.
*Contact factory for dice specifications.
Devices in PDIP and SO packages are available in both leaded
and lead-free packaging. Specify lead free by adding the +
symbol at the end of the part number when ordering. Lead free
not available for CERDIP package.
TD
0.099"
(2.51 mm)
ST
TOL
Package Information
For the latest package outline information, go to
www.maxim-ic.com/packages.
RST
GND
RST
0.070"
(1.78 mm)
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.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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