Maxim DS1706SEPA 3.3v and 5.0v micromonitor Datasheet

19-5212; Rev 4/10
DS1705/DS1706
3.3V and 5.0V MicroMonitor
www.maxim-ic.com
FEATURES
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PIN ASSIGNMENT
Halts and restarts an out-of-control
microprocessor
Holds microprocessor in check during power
transients
Automatically restarts microprocessor after
power failure
Monitors pushbutton for external override
Accurate 5%, 10% or 20% resets for 3.3V
systems and 5% or 10% resets for 5.0V
systems
Eliminates the need for discrete components
3.3V 20% tolerance for use with 3.0V
systems
Pin-compatible with the MAXIM
MAX705/MAX706 in 8-pin DIP, 8-pin SOIC,
and -SOP
8-pin DIP, 8-pin SOIC and 8-pin -SOP
packages
Industrial temperature range -40C to +85C
PBRST
1
8
WDS
VCC
2
7
RST
GND
3
6
ST
IN
4
5
NMI
8-Pin DIP (300 -mil)
PBRST
1
8
WDS
VCC
2
7
RST(*RST)
GND
3
6
ST
IN
4
5
NMI
8-Pin SOIC (150-mil)
RST(*RST)
WDS
PBRST
VCC
1
2
3
4
8
7
6
5
ST
NMI
IN
GND
8-Pin -SOP (118-mil)
See Mech. Drawings Section on website
DS1705 and DS1706_R/S/T
(*DS1706L and DS1706P)
PIN DESCRIPTION
PBRST
VCC
GND
IN
NMI
ST
RST
*RST
WDS
- Pushbutton Reset Input
- Power Supply
- Ground
- Input
- Non-maskable Interrupt
- Strobe Input
- Active Low Reset Output
- Active High Reset Output
(DS1706P and DS1706L only)
- Watchdog Status Output
DESCRIPTION
The DS1705/DS1706 3.3- or 5.0-Volt MicroMonitor monitors three vital conditions for a microprocessor:
power supply, software execution, and external override. A precision temperature compensated reference
and comparator circuit monitor the status of VCC at the device and at an upstream point for maximum
protection. When the sense input detects an out-of-tolerance condition, a non-maskable interrupt is
generated. As the voltage at the device degrades, an internal power fail signal is generated which forces
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DS1705/DS1706
the reset to an active state. When VCC returns to an in-tolerance condition, the reset signal is kept in the
active state for a minimum of 130 ms to allow the power supply and processor to stabilize.
The second function the DS1705/DS1706 performs is pushbutton reset control. The DS1705/DS1706
debounces the pushbutton input and guarantees an active reset pulse width of 130 ms minimum.
The third function is a watchdog timer. The DS1705/DS1706 has an internal timer that forces the WDS
output signal to the active state if the strobe input is not driven low prior to time-out.
OPERATION
Power Monitor
The DS1705/DS1706 detects out-of-tolerance power supply conditions and warns a processor-based
system of impending power failure. When VCC falls below the minimum VCC tolerance, a comparator
outputs the RST (or RST) signal. RST (or RST) is an excellent control signal for a microprocessor, as
processing is stopped at the last possible moment of valid VCC. On power-up, RST (or RST) are kept
active for a minimum of 130 ms to allow the power supply and processor to stabilize.
Pushbutton Reset
The DS1705/DS1706 provides an input pin for direct connection to a pushbutton reset (see Figure 2). The
pushbutton reset input requires an active low signal. Internally, this input is debounced and timed such
that a RST (or RST) signal of at least 130 ms minimum will be generated. The 130 ms delay commences
as the pushbutton reset input is released from the low level. The pushbutton can be initiated by connecting
the WDS or NMI outputs to the PBRST input as shown in Figure 3.
Non-Maskable Interrupt
The DS1705/DS1706 generates a non-maskable interrupt ( NMI ) for early warning of a power failure. A
precision comparator monitors the voltage level at the IN pin relative to an on-chip reference generated
by an internal band gap. The IN pin is a high impedance input allowing for a user-defined sense point. An
external resistor voltage divider network (Figure 5) is used to interface with high voltage signals. This
sense point may be derived from a regulated supply or from a higher DC voltage level closer to the main
system power input. Since the IN trip point VTP is 1.25 volts, the proper values for R1 and R2 can be
determined by the equation as shown in Figure 5. Proper operation of the DS1705/DS1706 requires that
the voltage at the IN pin be limited to VCC. Therefore, the maximum allowable voltage at the supply being
monitored (VMAX) can also be derived as shown in Figure 5. A simple approach to solving the equation is
to select a value for R2 high enough to keep power consumption low, and solve for R1. The flexibility of
the IN input pin allows for detection of power loss at the earliest point in a power supply system,
maximizing the amount of time for system shutdown between NMI and RST (or RST).
When the supply being monitored decays to the voltage sense point, the DS1705/DS1706 pulses the NMI
output to the active state for a minimum 200 s. The NMI power-fail detection circuitry also has built-in
hysteresis of 100 V. The supply must be below the voltage sense point for approximately 5 s before a
low NMI will be generated. In this way, power supply noise is removed from the monitoring function,
preventing false interrupts. During a power-up, any detected IN pin levels below VTP by the comparator
are disabled from generating an interrupt until VCC rises to VCCTP. As a result, any potential NMI pulse
will not be initiated until VCC reaches VCCTP.
Connecting NMI to PBRST would allow non-maskable interrupt to generate an automatic reset when an
out-of-tolerance condition occurred in a monitored supply. An example is shown in Figure 3.
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DS1705/DS1706
Watchdog Timer
The watchdog timer function forces WDS signals active when the ST input is not clocked within the 1
second time-out period. Time-out of the watchdog starts when RST (or RST) becomes inactive. If a highto-low transition occurs on the ST input pin prior to time-out, the watchdog timer is reset and begins to
time out again. If the watchdog timer is allowed to time out, the WDS signal is driven active (low) for a
minimum of 130 ms. The ST input can be derived from many microprocessor outputs. The typical signals
used are the microprocessors address signals, data signals, or control signals. When the microprocessor
functions normally, these signals would, as a matter of routine, cause the watchdog to be reset prior to
time-out. To guarantee that the watchdog timer does not time out, a high-to-low transition must occur at
or less than the minimum watchdog time-out of 1 second. A typical circuit example is shown in Figure 6.
MICROMONITOR BLOCK DIAGRAM Figure 1
40k
180k
PUSH-BUTTON RESET Figure 2
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DS1705/DS1706
PUSH-BUTTON RESET CONTROLLED BY NMI AND WDS Figure 3
TIMING DIAGRAM: PUSHBUTTON RESET Figure 4
NON-MASKABLE INTERRUPT CIRCUIT EXAMPLE Figure 5
VSENSE =
R1 R2
X 1.25
R2
Example:
Therefore:
VMAX =
VSENSE
X VCC
VTP
VSENSE = 4.50V at the trip point
VCC = 3.3V
10 kΩ = R2
4.50
X 3.3 = 11.88V maximum
1.25
4.5 =
R1  10k
X 1.25
10k
4 of 12
R1 = 26 kΩ
DS1705/DS1706
WATCHDOG TIMER Figure 6
TIMING DIAGRAM: STROBE INPUT Figure 7
TIMING DIAGRAM: NON-MASKABLE INTERRUPT Figure 8
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DS1705/DS1706
TIMING DIAGRAM: POWER-DOWN Figure 9
6 of 12
DS1705/DS1706
TIMING DIAGRAM: POWER-UP Figure 10
7 of 12
DS1705/DS1706
ABSOLUTE MAXIMUM RATINGS
Voltage Range on VCC Pin Relative to Ground
Voltage Range on I/O Relative to Ground*
Operating Temperature Range
Storage Temperature Range
Lead Temperature (soldering, 10s)
Soldering Temperature (reflow)
Lead(Pb)-free
Containing lead(Pb)
-0.5V to +7.0V
-0.5V to (VCC + 0.5V)
-40C to +85C
-55C to +125C
+260C
+260C
+240C
This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation
sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect
reliability.
*The voltage input on IN, ST, and PBRST can be exceeded if the input current is less than 10 mA.
(TA = -40C to +85C)
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
SYMBOL
MIN
Supply Voltage
VCC
TYP
MAX
UNITS
NOTES
1.2
5.5
V
1
ST
and PBRST Input High Level
VIH
2.0
VCC-0.5
VCC+0.3
V
1, 3
1, 4
ST
and PBRST Input Low Level
VIL
-0.03
+0.5
V
1
DC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
(VCC = 1.2V to 5.5V, TA = -40C to +85C.)
MIN
TYP
MAX
UNITS NOTES
VCC Trip Point DS1705/DS1706L
VCCTP
4.50
4.65
4.75
V
1
VCC Trip Point DS1706
VCCTP
4.25
4.40
4.50
V
1
VCC Trip Point DS1706T
VCCTP
3.00
3.08
3.15
V
1
VCC Trip Point DS1706S
VCCTP
2.85
2.93
3.00
V
1
VCC Trip Point DS1706P or R
VCCTP
2.55
2.63
2.70
V
1
Input Leakage
IIL
-1.0
+1.0
A
2
Output Current @ 2.4V
IOH
A
3
Output Current @ 0.4V
IOL
10
mA
3
Output Voltage @ -500 A
VOH
VCC-0.3
V
3
Operating Current
@ VCC < 5.5V
ICC
60
A
5
Operating Current
@ VCC < 3.6V
ICC
50
A
5
IN Input Trip Point
VTP
1.30
V
1
350
1.20
VCC-0.1
1.25
CAPACITANCE
PARAMETER
Input Capacitance
Output Capacitance
SYMBOL
MIN
TYP
MAX
(TA = +25C)
UNITS NOTES
CIN
5
pF
COUT
7
pF
8 of 12
DS1705/DS1706
AC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
(VCC = 1.2V to 5.5V, TA = -40C to +85C.)
MIN
TYP
MAX
UNITS NOTES
tPB
150
Reset Active Time
tRST
130
Pulse Width
tST
10
PBRST
ST
= VIL
VCC Detect to RST and RST
VCC Slew Rate
VCC Detect to RST and RST
VCC Slew Rate
PBRST
Stable Low to RST and RST
tRPD
ns
205
5
tF
20
tRPU
130
tR
0
tTD
VIN Detect to NMI
tIPD
1.0
8
ms
ns
6
s
9
s
205
285
ms
7
ns
tPDLY
Watchdog Timeout
285
250
ns
1.6
2.2
s
8
5
8
s
9
NOTES:
1. All voltages are referenced to ground.
2. PBRST is internally pulled up to VCC with an internal impedance of 40 ktypical and the ST input is
internally pulled up to VCC with an internal impedance of 180 ktypical.
3. VCC ≥ 2.4V.
4. VCC < 2.4V.
5. Measured with outputs open and all inputs at VCC or ground.
6. Must not exceed tTD minimum.
7. tR = 5 s.
8. Minimum watchdog time-out tested at 2.7V for the 3.3V devices and 4.5V for the 5.0V devices.
9. Noise immunity  pulses < 2 s will not cause a reset.
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DS1705/DS1706
PART MARKING CODES
DS170AB
yywwrv
8-pin DIP
(300 MIL)
8-pin SOIC
(150 MIL)
8-pin µSOP
(118 MIL)
CODE
AB
yww or yyww
rv
###xx
cccccc
cccccc
###xx
DS170AB
yywwrv
###xx
cccccc
170AB
ywwrv
###xx
BRAND CODES
DESCRIPTION
VALUES
Device type and tolerance
5_, 6_, 6L, 6P, 6R, 6S, 6T (where’_’ is a blank)
Date Code. Identifies the year and work y, the last digit of the year.
week the device was assembled.
yy, the last two digits of the year.
ww, the work week (values 01 through 52).
Die Revision
A letter followed by a number (eg. B1)
Lot Code
Three numbers followed by 2 letters
Country of Assembly
Abbreviation of country name.
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DS1705/DS1706
ORDERING INFORMATION
PART
DS1705EPA
DS1705ESA
DS1705EUA
DS1706EPA
DS1706ESA
DS1706EUA
DS1706LEPA
DS1706LESA
DS1706LEUA
DS1706PEPA
DS1706PESA
DS1706PEUA
DS1706REPA
DS1706RESA
DS1706REUA
DS1706SEPA
DS1706SESA
DS1706SEUA
DS1706TEPA
DS1706TESA
DS1706TEUA
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
8-pin PDIP (300 mils)
8-pin SO (150 mils)
8-pin µSOP (118 mils)
VERSION
5V-5% MONITOR, /RST, /WDS
5V-5% MONITOR, /RST, /WDS
5V-5% MONITOR, /RST, /WDS
5V-10% MONITOR, /RST, /WDS
5V-10% MONITOR, /RST, /WDS
5V-10% MONITOR, /RST, /WDS
5V-5% MONITOR, RST, /WDS
5V-5% MONITOR, RST, /WDS
5V-5% MONITOR, RST, /WDS
3.3V-20% MONITOR, RST, /WDS
3.3V-20% MONITOR, RST, /WDS
3.3V-20% MONITOR, RST, /WDS
3.3V-20% MONITOR, /RST, /WDS
3.3V-20% MONITOR, /RST, /WDS
3.3V-20% MONITOR, /RST, /WDS
3.3V-10% MONITOR, /RST, /WDS
3.3V-10% MONITOR, /RST, /WDS
3.3V-10% MONITOR, /RST, /WDS
3.3V-5% MONITOR, /RST, /WDS
3.3V-5% MONITOR, /RST, /WDS
3.3V-5% MONITOR, /RST, /WDS
Note: Devices are also available in a lead(Pb)-free/RoHS-compliant package. Specify lead-free by adding a plus (+) to the part number
when ordering.
E = -40°C to +85°C temperature range
A = 8-lead device
P = Plastic DIP (300 mils)
S = SO (150 mils)
U = µSOP (118 mils)
PACKAGE INFORMATION
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-”
in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
8 PDIP
8 SO
P8-2
S8-2
U8-1
21-0043
21-0041
21-0036
8 SOP
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DS1705/DS1706
REVISION HISTORY
REVISION
DATE
DESCRIPTION
PAGES
CHANGED
4/10
Added the lead temperature and updated the soldering
temperature in the Absolute Maximum Ratings; corrected Note 9.
8, 9
12 of 12
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.
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© 2010 Maxim Integrated Products
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