MAX706ATESA [MAXIM]
+3V Voltage Monitoring, Low-Cost uP Supervisory Circuits; + 3V的电压监测，低成本高达监控电路
| 型号： | MAX706ATESA |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | +3V Voltage Monitoring, Low-Cost uP Supervisory Circuits |
| 文件： | 总15页 (文件大小：466K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0099; Rev 5; 4/06
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
General Description
Features
The MAX706P/R/S/T, MAX706AP/AR/AS/AT, and
MAX708R/S/T microprocessor (µP) supervisory circuits
reduce the complexity and number of components
required to monitor +3V power-supply levels in +3V to
+5V µP systems. These devices significantly improve
system reliability and accuracy compared to separate
ICs or discrete components.
♦ µMAX Package, Small 8-Pin SO
♦ Precision Supply-Voltage Monitors
2.63V (MAX706P/R, MAX706AP/AR, and MAX708R)
2.93V (MAX706S, MAX706AS, and MAX708S)
3.08V (MAX706T, MAX706AT, and MAX708T)
♦ 200ms Reset Time Delay
The MAX706P/R/S/T and MAX706AP/AR/AS/AT supervi-
sory circuits provide the following four functions:
♦ Debounced TTL/CMOS-Compatible Manual Reset
Input
1) A reset output during power-up, power-down, and
brownout conditions.
♦ 100µA Quiescent Current
2) An independent watchdog output that goes low if the
watchdog input has not been toggled within 1.6s.
♦ WDI Disable Feature (MAX706AP/AR/AS/AT)
♦ Watchdog Timer: 1.6s Timeout
3) A 1.25V threshold detector for power-fail warning,
low-battery detection, or for monitoring a power
supply other than the main supply.
♦ Reset Output Signal:
Active-High Only (MAX706P, MAX706AP)
Active-Low Only (MAX706R/S/T, MAX706AR/AS/AT)
Active-High and Active-Low (MAX708R/S/T)
4) An active-low, manual-reset input.
The only difference between the MAX706R/AR,
MAX706S/AS, and MAX706T/AT is the reset-threshold
voltage levels, which are 2.63V, 2.93V, and 3.08V,
respectively. All have active-low reset output signals.
The MAX706P/AP are identical to the MAX706R/AR,
except the reset output signal is active-high. The watch-
dog timer function for the MAX706AP/AR/AS/AT dis-
ables when the WDI input is left open or connected to a
high-impedance state of a low-leakage tri-state output.
♦ Voltage Monitor for Power-Fail or Low-Battery
Warning
♦ 8-Pin Surface-Mount Package
♦ Guaranteed RESET Assertion to V
= 1V
CC
Ordering Information
TEMP
RANGE
PIN-
PACKAGE
PKG
CODE
PART†
The MAX708R/S/T provide the same functions as the
MAX706R/S/T and MAX706AR/AS/AT except they do
not have a watchdog timer. Instead, they provide both
RESET and RESET outputs. As with the MAX706,
devices with R, S, and T suffixes have reset thresholds
of 2.63V, 2.93V, and 3.08V, respectively.
MAX706PCPA
MAX706PCSA
MAX706PCUA
MAX706PEPA
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
8 PDIP
8 SO
P8-1
S8-2
U8-1
P8-1
8 µMAX
8 PDIP
†
SO, µMAX, and PDIP packages are available in lead-free.
These devices are available in 8-pin SO, DIP, and
µMAX® packages and are fully specified over the oper-
ating temperature range.
Ordering Information continued at end of data sheet.
Pin Configurations appear at end of data sheet.
Typical Operating Circuits
Applications
UNREGULATED
Battery-Powered Equipment
Portable Instruments
Computers
DC-DC
DC
CONVERTER
+3V/+3.3V
MAX639
V
CC
µP
Controllers
MAX706R/S/T
MAX706AR/AS/AT
Intelligent Instruments
Critical µP Power Monitoring
V
CC
RESET
RESET
I/O LINE
WDI
WDO
PFO
PFI
MR
NMI
PUSHBUTTON
SWITCH
INTERRUPT
GND
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ 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.
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
........................................................................-0.3V to +6V
8-Pin SO (derate 5.9mW/°C above +70°C)................470.6mW
8-Pin µMAX (derate 4.5mW/ C above +70°C)..............362mW
Operating Temperature Range
MAX70_C.............................................................0°C to +70°C
MAX70_E ..........................................................-40°C to +85°C
MAX70_M .......................................................-55°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
o
V
CC
All Other Inputs (Note 1)..........................-0.3V to (V
Input Current
+ 0.3V)
CC
V
..................................................................................20mA
CC
GND .................................................................................20mA
Output Current (all outputs) ................................................20mA
Continuous Power Dissipation (T = +70°C)
A
8-Pin CERDIP (derate 8mW/°C above +70°C)..............640mW
8-Pin PDIP (derate 9.1mW/°C above +70°C).............727.3mW
Note 1: The input-voltage limits on PFI, WDI, and MR can be exceeded if the input current is less than 10mA.
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
(MAX70_P/R, MAX706AP/AR: V
= 2.7V to 5.5V; MAX70_S, MAX706AS: V
= 3.0V to 5.5V; MAX70_T, MAX706AT: V = 3.15V to
CC
CC
CC
J
5.5V; T = T = T
to T
, unless otherwise noted. Typical values are at T = T = +25°C.) (Note 2)
J
A
MIN
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
1.0
TYP
MAX
UNITS
MAX70_C
5.5
5.5
Supply Voltage Range
V
V
CC
MAX70_E/M
MAX706_C
MAX706_E/M
MAX708_C
MAX708_E/M
MAX706_C
MAX706_E/M
MAX708_C
MAX708_E/M
1.2
90
90
200
300
200
300
350
500
350
500
2.70
3.00
3.15
V
V
< 3.6V
< 5.5V
CC
CC
50
50
Supply Current
I
µA
SUPPLY
135
135
65
65
MAX70_P/R/, MAX706AP/AR
MAX70_S, MAX706AS
MAX70_T, MAX706AT
2.55
2.85
3.00
2.63
2.93
3.08
Reset Threshold (Note 3)
V
V
V
RST
HYS
RST
(V
CC
Falling)
Reset Threshold Hysteresis
(Note 3)
20
mV
ms
MAX70_P/R/, MAX706AP/AR V
= 3.0V
140
140
200
200
200
280
280
CC
Reset Pulse Width (Note 3)
t
MAX70_S, MAX706AS, V
= 3.3V
CC
V
= 5V
CC
RESET OUTPUT
0.8 x
V
V
V
< V
< V
< 3.6V
< 3.6V
I
= 500µA
SOURCE
OH
RST(MAX)
RST(MAX)
CC
CC
V
CC
V
I
I
= 1.2mA
0.3
OL
SINK
Output-Voltage High
(MAX70_R/S/T)
=
V
-
CC
RSOURCE
V
4.5V < V
< 5.5V
CC
V
OH
800µA
1.5
(MAX706AR/AS/AT)
V
V
4.5V < V < 5.5V
I
SINK
= 3.2mA
0.4
0.3
0.3
OL
OL
CC
MAX70_C V
= 1.0V, I
= 50µA
CC
SINK
MAX70_E/M: V
= 1.2V, I
= 100µA
CC
SINK
2
_______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(MAX70_P/R, MAX706AP/AR: V
= 2.7V to 5.5V; MAX70_S, MAX706AS: V
= 3.0V to 5.5V; MAX70_T, MAX706AT: V = 3.15V to
CC
CC
CC
J
5.5V; T = T = T
to T
, unless otherwise noted. Typical values are at T = T = +25°C.) (Note 2)
J
A
MIN
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
0.6
-
CC
V
V
V
< V
< V
< 3.6V
< 3.6V
I
I
I
= 215µA
= 800µA
OH
RST(MAX)
RST(MAX)
CC
CC
SOURCE
V
= 1.2mA
0.3
OL
SINK
Output-Voltage High
(MAX706P) (MAX706AP)
V
V
V
1.5
-
CC
V
4.5 < V
< 5.5V
OH
CC
SOURCE
V
4.5V < V
< 5.5V
I
I
I
= 3.2mA
0.4
0.3
OL
CC
SINK
V
V
V
< V
< 3.6V
= 500µA 0.8xV
SOURCE CC
OH
RST(MAX)
CC
CC
V
< V
< 3.6V
= 500µA
SINK
OL
RST(MAX)
Output-Voltage High
(MAX708_)
V
1.5
-
CC
V
4.5V < V
4.5V < V
< 5.5V
< 5.5V
I
= 800µA
OH
CC
CC
SOURCE
V
I
= 1.2mA
SINK
0.4
OL
WATCHDOG INPUT
MAX706P/R, MAX706AP/AR, V
= 3.0V
= 3.3V
1.00
1.00
1.60
1.60
2.25
2.25
CC
Watchdog Timeout Period
t
s
WD
MAX706S/T, MAX706AS/AT, V
CC
V
< V
CC
RST(MAX)
V
= 0.4V
100
50
IL
WDI Pulse Width
(MAX706_, MAX706A_)
< 3.6V
4.5V < V
5.5V
t
ns
WP
<
CC
V
V
= 0.8V x V
IH
CC
V
< V
< V
< 3.6V
< 3.6V
0.6
0.8
IL
RST(MAX)
CC
CC
0.7 x
V
V
IH
RST(MAX)
Watchdog Input Threshold
(MAX706_, MAX706A_)
V
CC
V
V
V
V
= 5.0V
= 5.0V
IL
CC
CC
V
3.5
-1.0
-5
IH
MAX706_
+0.02
+1.0
+5
WDI Input Current
WDI = 0V or V
µA
CC
MAX706A_
_______________________________________________________________________________________
3
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(MAX70_P/R, MAX706AP/AR: V
= 2.7V to 5.5V; MAX70_S, MAX706AS: V
= 3.0V to 5.5V; MAX70_T, MAX706AT: V = 3.15V to
CC
CC
CC
J
5.5V; T = T = T
to T
, unless otherwise noted. Typical values are at T = T = +25°C.) (Note 2)
J
A
MIN
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
WATCHDOG OUTPUT
0.8 x
V
V
V
< V
< V
< 3.6V
< 3.6V
I
I
I
I
= 500µA
= 800µA
OH
RST(MAX)
RST(MAX)
CC
CC
SOURCE
V
CC
V
= 500µA
0.3
0.4
OL
SINK
WDO Output Voltage
(MAX706_, MAX706A_)
V
V
-
CC
V
4.5V < V
4.5V < V
< 5.5V
< 5.5V
OH
CC
CC
SOURCE
1.5
V
= 1.2mA
SINK
OL
MANUAL RESET INPUT
V
< V
CC
RST(MAX)
25
70
250
600
< 3.6V
MR Pullup Current
MR = 0
µA
ns
4.5V < V
5.5V
<
CC
100
250
V
< V
< 3.6V
500
150
RST(MAX)
CC
MR Pulse Width
t
MR
4.5V < V
< 5.5V
CC
V
V
< V
< 3.6V
0.6
0.8
IL
RST(MAX)
CC
0.7 x
V
V
< V
RST(MAX)
< 3.6V
IH
CC
MR Input Threshold
V
CC
V
V
4.5V < V
4.5V < V
< 5.5V
< 5.5V
IL
CC
CC
V
2.0
IH
V
< V
< 3.6V
750
250
RST(MAX)
CC
MR to Reset Output Delay
t
ns
MD
4.5V < V
< 5.5V
CC
POWER-FAILURE COMPARATOR
(MAX70_P/R, MAX706AP/AR) PFI falling
= 3.0V
1.20
1.20
1.25
1.30
V
CC
PFI Input Threshold
PFI Input Current
V
(MAX70_S/T, MAX706AS/AT) PFI falling,
1.25
1.30
+25
V
= 3.3V
CC
-25
+0.01
nA
0.8 x
V
V
V
< V
< 3.6V
< 3.6V
I
I
I
I
= 500µA
= 800µA
OH
RST(MAX)
RST(MAX)
CC
CC
SOURCE
V
CC
V
< V
= 1.2mA
0.3
0.4
OL
SINK
PFO Output Voltage
V
V
-
CC
V
4.5V < V
4.5V < V
< 5.5V
< 5.5V
OH
CC
SOURCE
1.5
V
= 3.2mA
SINK
OL
CC
Note 2: All devices 100% production tested at T = +85°C. Limits over temperature are guaranteed by design.
A
Note 3: Applies to both RESET in the MAX70_R/S/T and MAX706AR/AS/AT, and RESET in the MAX706P/MAX706AP.
4
_______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
_______________________________________________________________________________________
5
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Pin Description
PIN
MAX706P
MAX706AP
MAX706R/S/T,
MAX706AR/AS/AT
NAME
FUNCTION
MAX708R/S/T
SO/DIP
µMAX SO/DIP
µMAX SO/DIP µMAX
Active-Low, Manual-Reset Input. Pull MR below 0.6V to trigger a
reset pulse. MR is TTL/CMOS compatible when V = 5V and can
be shorted to GND with a switch. MR is internally connected to a
CC
1
3
1
3
1
3
MR
70µA source current. Connect to V or leave unconnected.
CC
2
3
4
5
2
3
4
5
2
3
4
5
V
Supply Voltage Input
CC
GND Ground
Adjustable Power-Fail Comparator Input. Connect PFI to a
resistive divider to set the desired PFI threshold. When PFI is
less than 1.25V, PFO goes low and sinks current; otherwise,
PFO remains high. Connect PFI to GND if not used.
4
5
6
7
4
5
6
7
4
5
6
7
PFI
Active-Low, Power-Fail Comparator Output. PFO asserts when
PFI is below the internal 1.25V threshold. PFO deasserts when
PFI is above the internal 1.25V threshold. Leave PFO
unconnected if not used.
PFO
Watchdog Input. A falling or rising transition must occur at
WDI within 1.6s to prevent WDO from asserting (see Figure 4).
The internal watchdog timer is reset to zero when reset is
asserted or when transition occurs at WDI. The watchdog
6
8
6
8
—
—
WDI function for the MAX706P/R/S/T can not be disabled. The
watchdog timer for the MAX706AP/AR/AS/AT disables when
WDI input is left open or connected to a tri-state output in its
high-impedance state with a leakage current of less than
600nA.
Active-High Reset Output. Reset remains high when V
is
CC
below the reset threshold or MR is held low. It remains low for
200ms after the reset conditions end (Figure 3).
7
8
1
2
—
8
—
2
8
2
RESET
Active-Low Watchdog Output. WDO goes low when a
transition does not occur at WDI within 1.6s and remains low
until a transition occurs at WDI (indicating the watchdog
—
—
WDO
interrupt has been serviced). WDO also goes low when V
CC
falls below the reset threshold; however, unlike the reset
output signal, WDO goes high as soon as V
rises above
CC
the reset threshold.
Active-Low Reset Output. RESET remains low when V
is
CC
—
—
—
—
7
1
7
6
1
8
RESET below the reset threshold or MR is held low. It remains low for
200ms after the reset conditions end (Figure 3).
—
—
N.C. No Connection. Not internally connected.
6
_______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
WATCHDOG
TRANSITION
DETECTOR
6
WATCHDOG
8
WDI
MR
WDO
TIMER
V
CC
8
7
RESET
RESET
V
70µA
CC
TIMEBASE FOR
RESET AND
WATCHDOG
1
2
MR
70µA
RESET
GENERATOR
1
2
V
CC
7
5
RESET
GENERATOR
RESET
(RESET)
V
CC
2.63V MAX708R
2.93V MAX708S
3.08V MAX708T
MAX708R/S/T
2.63V MAX706P/R
2.93V MAX706S
3.08V MAX706T
4
PFI
MAX706P/R/S/T
MAX706AP/AR/AS/AT
5
PFO
4
PFI
PFO
1.25V
1.25V
3
GND
3
GND
( ) ARE FOR MAX706P/AP.
Figure 1. MAX706_ Functional Diagram
Figure 2. MAX708_ Functional Diagram
RESET and RESET are guaranteed to be asserted for
≥ 1V.
RESET and RESET Outputs
A microprocessor’s (µP’s) reset input starts in a known
state. When the µP is in an unknown state, it should be
held in reset. The MAX706P/R/S/T and the MAX706AP/
V
CC
The MAX706P/MAX706AP provide a RESET signal, and
the MAX706R/S/T and MAX706AR/AS/AT provide a
RESET signal. The MAX708R/S/T provide both RESET
and RESET.
AR/AS/AT assert reset when V
is low, preventing
CC
code execution errors during power-up, power-down,
or brownout conditions.
Watchdog Timer
The MAX706P/R/S/T and the MAX706AP/AR/AS/AT
watchdog circuit monitor the µP’s activity. If the µP
does not toggle the watchdog input (WDI) within 1.6s,
the watchdog output (WDO) goes low (Figure 4). If the
reset signal is asserted, the watchdog timer will be
reset to zero and disabled. As soon as reset is
released, the timer starts counting. WDI can detect puls-
es as narrow as 100ns with a 2.7V supply and 50ns with a
4.5V supply. The watchdog timer for the MAX706P/R/S/T
cannot be disabled. The watchdog timer for the
MAX706AP/AR/AS/AT operates similarly to the
MAX706P/R/S/T. However, the watchdog timer for the
MAX706AP/AR/AS/AT disables when the WDI input is
left open or connected to a tri-state output in its high-
impedance state and with a leakage current of less
than 600nA. The watchdog timer can be disabled any-
time, provided WDO is not asserted.
On power-up once V
reaches 1V, RESET is guaran-
CC
teed to be logic-low and RESET is guaranteed to be
logic-high. As V
rises, RESET and RESET remain
CC
CC
asserted. Once V
exceeds the reset threshold, the
internal timer causes RESET and RESET to be
deasserted after a time equal to the reset pulse width,
which is typically 200ms (Figure 3).
If a power-fail or brownout condition occurs (i.e., V
drops below the reset threshold), RESET and RESET
are asserted. As long as V remains below the reset
CC
CC
threshold, the internal timer is continually reset, causing
the RESET and RESET outputs to remain asserted.
Thus, a brownout condition that interrupts a previously
initiated reset pulse causes an additional 200ms delay
from the time the latest interruption occurred. On
power-down once V
drops below the reset threshold,
CC
_______________________________________________________________________________________
7
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
+3.3V
V
RST
V
RST
V
CC
+1V
t
t
RST
RST
+3V/+3.3V
+12V
RESET
RESET
(RESET)
0V
V
TO µP
CC
1MΩ
1%
+3.3V
MAX706_
MAX708R/S/T
RESET
0V
+3.3V
0V
MR
130kΩ
1%
PFI
PFO
MR*
GND
t
MD
t
MR
+3.3V
0V
*NOTE: MR EXTERNALLY DRIVEN LOW.
PARAMETER
+12V RESET
THRESHOLD AT +25°C
( ) ARE FOR MAX706P/AP
MIN
TYP MAX UNIT
WDO*
WDO TIMING SHOWN FOR MAX706P/R/S/T.
10.24 10.87 11.50
V
Figure 3. RESET, RESET, MR, and WDO Timing
t
WP
t
t
t
WD
WD
WD
+3V/+3.3V
WDI
Figure 5. Monitoring Both +3V/+3.3V and +12V
0V
+3V/+3.3V
WDO
0V
+3V/+3.3V
MAX706R/S/T
MAX708R/S/T
MAX706AR/AS/AT
RESET
0V
RESET EXTERNALLY
TRIGGERED BY MR
t
RST
RESET
Figure 4. MAX706AP/AR/AS/AT Watchdog Timing
R1
WDO can be connected to the nonmaskable interrupt
(NMI) input of a µP. When V drops below the reset
CC
threshold, WDO immediately goes low, even if the
watchdog timer has not timed out (Figure 3). Normally,
this would trigger an NMI, but since reset is asserted
simultaneously, the NMI is overridden. The WDO
should not be connected to RESET directly. Instead,
connect WDO to MR to generate a reset pulse when it
times out.
Figure 6. RESET Valid to GND Circuit
input pulse width is 500ns when V
= +3V and 150ns
CC
when V
= +5V. Leave MR unconnected or connect
CC
to V
when not used.
CC
Power-Fail Comparator
The power-fail comparator can be used for various pur-
poses because its output and noninverting input are
not internally connected. The inverting input is internally
connected to a 1.25V reference. The power-fail com-
parator has 10mV of hysteresis, which prevents repeat-
ed triggering of the power-fail output (PFO).
Manual Reset
The manual reset (MR) input allows RESET and RESET
to be activated by a pushbutton switch. The switch is
effectively debounced by the 140ms minimum reset
pulse width. MR can be driven by an external logic line
since it is TTL/CMOS compatible. The minimum MR
8
_______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
To build an early-warning power-failure circuit, use the
V
IN
power-fail comparator input (PFI) to monitor the unregu-
lated DC supply voltage (see the Typical Operating
Circuits). Connect the PFI to a resistive-divider network
such that the voltage at PFI falls below 1.25V just
before the regulator drops out. Use PFO to interrupt the
µP so it can prepare for an orderly power-down.
+3V/+3.3V
R1
V
CC
PFI
C1*
MAX706_
MAX708R/S/T
Regulated and unregulated voltages can be monitored
by simply adjusting the PFI resistive-divider network
values to the appropriate ratio. In addition, the reset
R3
R2
PFO
signal can be asserted at voltages other that V
reset
CC
GND
threshold, as shown in Figure 5. Connect PFO to MR to
initiate a reset pulse when the 12V supply drops below
a user-specified threshold (11V in this example) or
TO µP
*OPTIONAL
+3V/+3.3V
PFO
when V
falls below the reset threshold.
CC
Operation with +3V and +5V Supplies
0V
The MAX706P/R/S/T, the MAX706AP/AR/AS/AT, and the
MAX708R/S/T provide voltage monitoring at the reset
threshold (2.63V to 3.08V) when powered from either
+3V or +5V. These devices are ideal in portable-instru-
ment applications where power can be supplied from
either a +3V battery or an AC-DC wall adapter that gen-
erates +5V (a +5V supply allows a µP or a microcon-
troller to run faster than a +3V supply). With a +3V
supply, these ICs consume less power, but output drive
capability is reduced, the MR to RESET delay time
increases, and the MR minimum pulse width increases.
The Electrical Characteristics table provides specifica-
tions for operation with both +3V and +5V supplies.
0V
V
V
V
V
L
TRIP
IN
H
-
(R1 + R2)
R2
V
V
= 1.25
TRIP
R3 + R2
R2 × R3
1.25
R2
V
- 1.25
R3
CC
= 1.25 (1 +
R1) V = 1.25 + R1
L
H
Figure 7. Adding Hysteresis to the Power-Fail Comparator
+3V/+3.3V
R1
Ensuring a Valid RESET Output Down to
V
CC
V
= 0V
CC
PFO
PFI
When V
falls below 1V, the MAX706R/S/T,
CC
MAX706AR/AS/AT, and MAX708R/S/T RESET output no
longer sinks current; it becomes an open circuit. High-
impedance, CMOS logic inputs can drift to undeter-
mined voltages if left as open circuit. If a pulldown
resistor is added to the RESET pin , as shown in Figure
6, any stray charge or leakage current will flow to
ground, holding RESET low. Resistor value R is not criti-
cal, but it should not load RESET and should be small
enough to pull RESET and the input it is driving to
ground. 100kΩ is suggested for R1.
MAX706_
MAX708R/S/T
R2
GND
V-
+3V/+3.3V
PFO
0V
V
TRIP
V-
0V
V
CC
- 1.25 1.25 - V
TRIP
=
R1
R2
Applications Information
NOTE: V
IS NEGATIVE.
TRIP
Adding Hysteresis to the Power-Fail
Comparator
Hysteresis adds a noise margin to the power-fail com-
parator and prevents repeated triggering of the PFO
Figure 8. Monitoring a Negative Voltage
when V is near the power-fail comparator trip point.
IN
Figure 7 shows how to add hysteresis to the power-fail
comparator. Select the ratio of R1 and R2 such that PFI
_______________________________________________________________________________________
9
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
sees 1.25V when V falls to the desired trip point
TRIP
Monitoring a Negative Voltage
The power-fail comparator can be used to monitor a
negative supply voltage using the circuit of Figure 8.
When the negative supply is valid, PFO is low. When
the negative supply voltage drops, PFO goes high. This
circuit’s accuracy is affected by the PFI threshold toler-
IN
(V
). Resistor R3 adds hysteresis. R3 will typically
be an order of magnitude greater than R1 and R2. The
current through R1 and R2 should be at least 1µA to
ensure that the 25nA (max) PFI input current does not
shift the trip point significantly. R3 should be larger than
10kΩ to prevent it from loading down the PFO pin.
Capacitor C1 adds noise rejection.
ance, the V
voltage, and resistors R1 and R2.
CC
Bypassing V
CC
with a 0.1µF capacitor
For noisy systems, bypass V
to GND.
CC
Ordering Information (continued)
TEMP
RANGE
PIN-
PACKAGE
PKG
CODE
TEMP
RANGE
PIN-
PACKAGE
PKG
CODE
PART†
PART†
MAX706ASESA
MAX706ASEUA
MAX706ATEPA
MAX706ATESA
MAX706ATEUA
MAX708RCPA
MAX708RCSA
MAX708RCUA
MAX708REPA
MAX708RESA
MAX708REUA
MAX708RMJA
MAX708SCPA
MAX708SCSA
MAX708SCUA
MAX708SEPA
MAX708SESA
MAX708SEUA
MAX708SMJA
MAX708TCPA
MAX708TCSA
MAX708TCUA
MAX708TEPA
MAX708TESA
MAX708TEUA
MAX708TMJA
-40°C to +85°C 8 SO
S8-2
U8-1
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
J8-2
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
J8-2
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
J8-2
MAX706PEUA
MAX706PMJA
MAX706RCPA
MAX706RCSA
MAX706RCUA
MAX706REPA
MAX706RESA
MAX706REUA
MAX706RMJA
MAX706SCPA
MAX706SCSA
MAX706SCUA
MAX706SEPA
MAX706SESA
MAX706SEUA
MAX706SMJA
MAX706TCPA
MAX706TCSA
MAX706TCUA
MAX706TEPA
MAX706TESA
MAX706TEUA
MAX706TMJA
MAX706APEPA
MAX706APESA
MAX706APEUA
-40°C to +85°C 8 µMAX
U8-1
J8-2
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
J8-2
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
J8-2
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
J8-2
P8-1
S8-2
U8-1
P8-1
S8-2
U8-1
P8-1
-40°C to +85°C 8 µMAX
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
-55°C to +125°C 8 CERDIP*
0°C to +70°C
0°C to +70°C
0°C to +70°C
8 Plastic Dip
8 SO
-40°C to +85°C 8 µMAX
8 µMAX
0°C to +70°C
0°C to +70°C
0°C to +70°C
8 Plastic Dip
8 SO
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
8 µMAX
-40°C to +85°C 8 µMAX
-55°C to +125°C 8 CERDIP*
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
0°C to +70°C
0°C to +70°C
0°C to +70°C
8 Plastic Dip
8 SO
-40°C to +85°C 8 µMAX
-55°C to +125°C 8 CERDIP*
8 µMAX
0°C to +70°C
0°C to +70°C
0°C to +70°C
8 Plastic Dip
8 SO
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
8 µMAX
-40°C to +85°C 8 µMAX
-55°C to +125°C 8 CERDIP*
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
0°C to +70°C
0°C to +70°C
0°C to +70°C
8 Plastic Dip
8 SO
-40°C to +85°C 8 µMAX
-55°C to +125°C 8 CERDIP*
8 µMAX
0°C to +70°C
0°C to +70°C
0°C to +70°C
8 Plastic Dip
8 SO
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
8 µMAX
-40°C to +85°C 8 µMAX
-55°C to +125°C 8 CERDIP*
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
-40°C to +85°C 8 Plastic Dip
-40°C to +85°C 8 SO
-40°C to +85°C 8 µMAX
-55°C to +125°C 8 CERDIP*
-40°C to +85°C 8 µMAX
†
SO, µMAX, and PDIP packages are available in lead-free.
*Contact factory for availability and processing to MIL-STD-883.
**Future product—contact factory for availability.
MAX706AREPA -40°C to +85°C 8 Plastic Dip
MAX706ARESA
MAX706AREUA
MAX706ASEPA
-40°C to +85°C 8 SO
-40°C to +85°C 8µMAX
-40°C to +85°C 8 Plastic Dip
Chip Information
PROCESS: CMOS
10 ______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Pin Configurations
Typical Operating Circuits
(continued)
TOP VIEW
MR
WDO
1
2
3
4
UNREGULATED
DC
8
DC-DC
V
RESET
WDI
7
6
5
CC
GND
PFI
CONVERTER
-3V/+3.3V
MAX639
MAX706P
MAX706AP
µP
PFO
V
CC
V
CC
DIP/SO
RESET
RESET
PFO
RESET
PFI
INTERRUPT
MR
1
2
3
4
WDO
RESET
WDI
8
7
6
5
MR
PUSHBUTTON
SWITCH
GND
V
CC
MAX708R/S/T
MAX706R/S/T
MAX706AR/AS/AT
GND
PFI
PFO
DIP/SO
1
2
3
4
RESET
RESET
N.C.
8
7
6
5
MR
V
CC
MAX708R/S/T
GND
PFI
PFO
DIP/SO
(RESET) RESET
1
2
3
4
WDI
PFO
PFI
8
7
6
5
WDO
MR
MAX706P/R/S/T
MAX706AP/AR/
AS/AT
V
CC
GND
µMAX
RESET
RESET
MR
N.C.
PFO
PFI
1
2
3
4
8
7
6
5
MAX708R/S/T
V
CC
GND
µMAX
( ) ARE FOR MAX706P/AP ONLY.
______________________________________________________________________________________ 11
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
12 ______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
4X S
8
8
MILLIMETERS
INCHES
DIM MIN
MAX
MAX
MIN
-
-
0.043
0.006
0.037
0.014
0.007
0.120
1.10
0.15
0.95
0.36
0.18
3.05
A
0.002
0.030
0.010
0.005
0.116
0.05
0.75
0.25
0.13
2.95
A1
A2
b
E
H
Ø0.50±0.1
c
D
e
0.0256 BSC
0.65 BSC
0.6±0.1
E
H
0.116
0.188
0.016
0°
0.120
2.95
4.78
0.41
0°
3.05
5.03
0.66
6°
0.198
0.026
6°
L
1
1
α
S
0.6±0.1
0.0207 BSC
0.5250 BSC
BOTTOM VIEW
D
TOP VIEW
A1
A2
A
c
α
e
L
b
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0036
J
1
______________________________________________________________________________________ 13
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
INCHES
MILLIMETERS
MAX
MAX
1.75
0.25
0.49
0.25
DIM
A
MIN
MIN
1.35
0.10
0.35
0.19
0.053
0.004
0.014
0.007
0.069
0.010
0.019
0.010
N
A1
B
C
e
0.050 BSC
1.27 BSC
E
0.150
0.228
0.016
0.157
0.244
0.050
3.80
5.80
0.40
4.00
6.20
1.27
E
H
H
L
VARIATIONS:
INCHES
1
MILLIMETERS
MAX
0.197
0.344
0.394
MAX
5.00
DIM
D
MIN
MIN
4.80
8.55
9.80
N
8
MS012
AA
TOP VIEW
0.189
0.337
0.386
D
8.75 14
10.00 16
AB
D
AC
D
C
A
B
0∞-8∞
e
A1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0041
B
1
14 ______________________________________________________________________________________
+3V Voltage Monitoring, Low-Cost µP
Supervisory Circuits
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15
© 2006 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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