S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
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June 2010 Rev. 2.0.0
Exar Corporation www.exar.com
48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 – Fax. +1 510 668-7001
GENERAL DESCRIPTION
The SP706R/S/T and SP708R/S/T series is a
family of microprocessor (µP) supervisory
circuits that integrate myriad components
involved in discrete solutions which monitor
power-supply and battery in µP and digital
systems.
The SP706R/S/T and SP708R/S/T series will
significantly improve system reliability and
operational efficiency when compared to
solutions obtained with discrete components.
The features of the SP706R/S/T and
SP708R/S/T series include a watchdog timer, a
µP reset, a Power Fail Comparator, and a
manual-reset input.
The SP706R/S/T and SP708R/S/T series is
ideal for 3.0V or 3.3V applications in
automotive systems, computers, controllers,
and intelligent instruments. The SP706R/S/T
and SP708R/S/T series is an ideal solution for
systems in which critical monitoring of the
power supply to the µP and related digital
components is demanded.
APPLICATIONS
Processors & DSPs Based Systems
Industrial & Medical Instruments
FEATURES
Precision Low Voltage Monitor
SP706R/SP708R: +2.63V
SP706S/SP708S: +2.93V
SP706T/SP708T: +3.08V
200ms RESET Pulse Width
SP706R/S/T: Active Low
SP708R/S/T: Active High and Active Low
Independent Watchdog Timer
1.6s Timeout (SP706R/S/T)
Enable/Disable Function
40µA Maximum Supply Current
Debounced TTL/CMOS Manual Reset
Input
RESET Asserted Down to V
CC
=1V
V
CC
Glitch Immunity
Voltage Monitor for Power Failure or
Low Battery Warning
8-Pin NSOIC and MSOP Packages
Pin Compatible with Industry
Standards 706R/S/T and 708R/S/T
Part Number RESET Threshold RESET Active Manual RESET Watchdog PFI Accuracy
SP706R 2.63V Low Yes
Yes 4%
SP706S 2.93V Low Yes
Yes 4%
SP706T 3.08V Low Yes
Yes 4%
SP708R 2.63V Low and High Yes No 4%
SP708S 2.93V Low and High Yes No 4%
SP708T 3.08V Low and High Yes No 4%
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
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© 2010 Exar Corporation 2/16 Rev. 2.0.0
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
V
CC
.......................................................... -0.3V to 6.0V
All Other Inputs (Note 1) ................... -0.3V to (V
CC
+0.3V)
Input Current
VCC ................................................................. 20mA
GND ................................................................ 20mA
Output Current (All outputs) ............................... 20mA
ESD Rating (HBM - Human Body Model) .................... 2kV
Continuous Power Dissipation
SO (derate 5.88mW/°C above +70°C) ...............471mW
Mini SO (derate 4.10mW/°C above +70°C) ........330mW
Storage Temperature .............................. -65°C to 160°C
Lead Temperature (Soldering, 10 sec) ....................300°C
ELECTRICAL SPECIFICATIONS
Unless otherwise indicated, V
CC
= 2.7V to 5.5V (SP70xR), V
CC
= 3.15V to 5.5V (SP70xS), V
CC
= 3.0V to 5.5V (SP70xT), T
A
=
T
MIN
to T
MAX
, typical at 25°C.
Parameter Min. Typ. Max. Units Conditions
Operating Voltage Range V
CC
1.0 5.5 V
Supply Current I
SUPPLY
25 40 µA
MR=V
CC
or floating, WDI floating
Reset Threshold
2.55 2.63 2.70
V
SP706R. SP708R
2.85 2.93 3.00 SP706S. SP708S
3.00 3.08 3.15 SP706T. SP708T
Reset Threshold Hysteresis 20 mV
Note 2
Reset Pulse Width t
RS
140 200 280 ms
Note 2
RESET Output Voltage
V
V
OH
0.8xV
CC
V
RST(MAX)
<V
CC
<3.6V, I
SOURCE
=500µA
V
OL
0.3 V
RST(MAX)
<V
CC
<3.6V, I
SINK
=1.2mA
V
OH
V
CC
-1.5 4.5V<V
CC
<5.5V, I
SOURCE
=800µA
V
OL
0.4 4.5V<V
CC
<5.5V, I
SINK
=3.2mA
RESET Output Voltage
V
V
OH
V
CC
-0.6 V
RST(MAX)
<V
CC
<3.6V, I
SOURCE
=215µA
V
OL
0.3 V
RST(MAX)
<V
CC
<3.6V, I
SOURCE
=1.2mA
V
OH
V
CC
-1.5 4.5V<V
CC
<5.5V, I
SOURCE
=800µA
V
OL
0.4 4.5V<V
CC
<5.5V, I
SOURCE
=3.2mA
Watchdog Timeout Period t
WD
1.00 1.60 2.25 s V
CC
<3.6V
WDI Pulse Width t
WP
(note 1) 50 ns
V
IL
=0.4V, V
IH
=0.8xV
CC
WDI Input Threshold
V
V
IL
0.6 V
RST(MAX)
<V
CC
<3.6V
V
IH
0.7xV
CC
V
RST(MAX)
<V
CC
<3.6V
V
IL
0.8 V
CC
=5V
V
IH
3.5 V
CC
=5V
WDI Input Current -1 0.02 1 µA
WDI=0V or WDI=V
CC
WDO Output Voltage
V
V
IL
0.8xV
CC
V
RST(MAX)
<V
CC
<3.6V, I
SOURCE
=500µA
V
IH
0.3 V
RST(MAX)
<V
CC
<3.6V, I
SINK
=1.2mA
V
IL
V
CC
-1.5 4.5V<V
CC
<5.5V, I
SOURCE
=800µA
V
IH
0.4 4.5V<V
CC
<5.5V, I
SINK
=3.2mA
MR Pull-up Current 25 70 250 µA MR = 0V, V
RST(MAX)
<V
CC
<3.6V
100 250 600 MR = 0V, 4.5V<V
CC
<5.5V
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
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© 2010 Exar Corporation 3/16 Rev. 2.0.0
Parameter Min. Typ. Max. Units Conditions
MR Pulse Width t
MR
500
ns V
RST(MAX)
<V
CC
<3.6V
150 4.5V<V
CC
<5.5V
MR Input Threshold
V
V
IL
0.6 V
RST(MAX)
<V
CC
<3.6V
V
IH
0.7xV
CC
V
RST(MAX)
<V
CC
<3.6V
V
IL
0.8 4.5V<V
CC
<5.5V
V
IH
2.0 4.5V<V
CC
<5.5V
MR to Reset Out Delay t
MD
750
ns V
RST(MAX)
<V
CC
<3.6V
250 4.5V<V
CC
<5.5V
PFI Input Threshold 1.20 1.25 1.30 V V
CC
=3.0V - SP70xR, PFI falling
V
CC
=3.3V - SP70xS/T, PFI falling
PFI Input Current -25.00 0.01 25.00 nA
PFO Output Voltage
V
V
IL
0.8xV
CC
V
RST(MAX)
<V
CC
<3.6V, I
SOURCE
=500µA
V
IH
0.3 V
RST(MAX)
<V
CC
<3.6V, I
SINK
=1.2mA
V
IL
V
CC
-1.5 4.5V<V
CC
<5.5V, I
SOURCE
=800µA
V
IH
0.4 4.5V<V
CC
<5.5V, I
SINK
=3.2mA
Note 1:WDI minimum rise /fall time is 1µs.
BLOCK DIAGRAM
Fig. 1: SP706R/S/T Block Diagram
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
L
Lo
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P
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© 2010 Exar Corporation 4/16 Rev. 2.0.0
Fig. 2: SP708R/S/T Block Diagram
PIN ASSIGNMENT
Fig. 3: Pin Assignment
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
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© 2010 Exar Corporation 5/16 Rev. 2.0.0
PIN DESCRIPTION
Name
Pin Number
Description
SP706R/S/T SP708R/S/T
SOIC MSOP SOIC MSOP
MR 1 3 1 3
Manual Reset
This input triggers a reset pulse when pulled below 0.8V. This active
LOW input has an internal 70µA pull-up current. It can be driven
from a TTL or CMOS logic line or shorted to ground with a switch.
V
CC
2 4 2 4
Voltage Input
GND 3 5 3 5
Ground reference for all signals
PFI 4 6 4 6
Power-Fail Input
When this voltage monitor input is less than 1.25V, PFO goes LOW.
Connect PFI to ground or V
CC
when not in use.
PFO 5 7 5 7
Power-Fail Output
This output is LOW until PFI is less then 1.25V
WDI 6 8 - -
Watchdog Input
If this input remains HIGH or LOW for 1.6s, the internal watchdog
timer times out and WDO goes LOW. Floating WDI or connecting WDI
to a high-impedance tri-state buffer disables the watchdog feature.
The internal watchdog timer clears whenever RESET is asserted, WDI
is tri-stated, or whenever WDI sees a rising or falling edge.
N.C. - - 6 8
No Connect
RESET 7 1 7 1
Active-LOW RESET Output
This output pulses LOW for 200ms when triggered and stays LOW
whenever V
CC
is below the reset threshold. It remains LOW for 200ms
after V
cc
rises above the reset threshold or MR goes from LOW to
HIGH. A watchdog timeout will not trigger RESET unless WDO is
connected to MR.
WDO 8 2 - -
Watchdog Output
This output pulls LOW when the internal watchdog timer finishes its
1.6s count and does not go HIGH again until the watchdog is cleared.
WDO also goes LOW during low-line conditions. Whenever V
CC
is
below the reset threshold, WDO stays LOW. However, unlike RESET,
WDO does not have a minimum pulse width. As soon as V
CC
is above
the reset threshold, WDO goes HIGH with no delay.
RESET - - 8 2
Active-HIGH RESET Output
This output is the complement of RESET. Whenever RESET is HIGH,
RESET is LOW and vice-versa. Note that the SP708R/S/T has a reset
output only.
ORDERING INFORMATION
Part Number Temperature
Range Marking Package Packing
Quantity Note 1 Note 2
SP706RCN-L 0°CT
A
+70°C
SP706RC
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP706RCN-L/TR 0°CT
A
+70°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP706RCU-L 0°CT
A
+70°C
706R
CXXX
YWW
8-pin MSOP Bulk Lead Free
SP706RCU-L/TR 0°CT
A
+70°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
SP706REN-L -40°CT
A
+85°C
SP706RE
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP706REN-L/TR -40°CT
A
+85°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP706REU-L -40°CT
A
+85°C
706R
EXXX
YWW
8-pin MSOP Bulk Lead Free
SP706REU-L/TR -40°CT
A
+85°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
SP706SCN-L 0°CT
A
+70°C
SP706SC
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP706SCN-L/TR 0°CT
A
+70°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP706SCU-L 0°CT
A
+70°C
706S
CXXX
YWW
8-pin MSOP Bulk Lead Free
SP706SCU-L/TR 0°CT
A
+70°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
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© 2010 Exar Corporation 6/16 Rev. 2.0.0
Part Number Temperature
Range Marking Package Packing
Quantity Note 1 Note 2
SP706SEN-L -40°CT
A
+85°C
SP706SE
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP706SEN-L/TR -40°CT
A
+85°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP706SEU-L -40°CT
A
+85°C
706S
EXXX
YWW
8-pin MSOP Bulk Lead Free
SP706SEU-L/TR -40°CT
A
+85°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
SP706TCN-L 0°CT
A
+70°C
SP706TC
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP706TCN-L/TR 0°CT
A
+70°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP706TCU-L 0°CT
A
+70°C
706T
CXXX
YWW
8-pin MSOP Bulk Lead Free
SP706TCU-L/TR 0°CT
A
+70°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
SP706TEN-L -40°CT
A
+85°C
SP706TE
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP706TEN-L/TR -40°CT
A
+85°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP706TEU-L -40°CT
A
+85°C
706T
EXXX
YWW
8-pin MSOP Bulk Lead Free
SP706TEU-L/TR -40°CT
A
+85°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
SP708REN-L -40°CT
A
+85°C
SP708RE
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP708REN-L/TR -40°CT
A
+85°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP708SCN-L 0°CT
A
+70°C
SP708SC
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP708SCN-L/TR 0°CT
A
+70°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP708SCU-L 0°CT
A
+70°C
708S
UXXX
YWW
8-pin MSOP Bulk Lead Free
SP708SCU-L/TR 0°CT
A
+70°C 8-pin MSOP 2.5K/Tape & Reel Lead Free
SP708SEN-L -40°CT
A
+85°C
SP708SE
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP708SEN-L/TR -40°CT
A
+85°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP708TCN-L 0°CT
A
+70°C
SP708TC
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP708TCN-L/TR 0°CT
A
+70°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
SP708TEN-L -40°CT
A
+85°C
SP706TE
YYWWL
X
8-pin NSOIC Bulk Lead Free
SP708TEN-L/TR -40°CT
A
+85°C 8-pin NSOIC 2.5K/Tape & Reel Lead Free
“YY” = Year – “WW” = Work Week – “X” = Lot Number
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
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© 2010 Exar Corporation 7/16 Rev. 2.0.0
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at V
CC
= 2.7V to 5.5V (SP70xR), V
CC
= 3.15V to 5.5V (SP70xS), V
CC
= 3.0V to 5.5V (SP70xT), T
A
= 25°C,
unless otherwise indicated.
Fig. 4: Power-Fail Comparator
De-Assertion Response Time
Fig. 5: Power-Fail Comparator
De-Assertion Response Time Circuit
Fig. 6: Power-Fail Comparator
Assertion Response Time
Fig. 7: Power-Fail Comparator
Assertion Response Time Circuit
Fig. 8: SP706 RESET Output Voltage
vs. Supply Voltage
Fig. 9: SP706 RESET Output Voltage
vs. Supply Voltage Circuit
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
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© 2010 Exar Corporation 8/16 Rev. 2.0.0
Fig. 10: SP706 RESET Response Time
Fig. 11: SP706 RESET Response Time Circuit
Fig. 12: SP708 RESET and RESET Assertion
Fig. 13: SP708 RESET and RESET De-Assertion
Fig. 14: SP708 RESET and RESET Assertion and De-Assertion Circuit
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
L
Lo
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P
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© 2010 Exar Corporation 9/16 Rev. 2.0.0
Fig. 15: SP708 RESET Output Voltage
vs. Supply Voltage
Fig. 16: SP708 RESET Response Time
Fig. 17: SP708 RESET Output Voltage vs. Supply Voltage
and SP813L RESET Response Time Circuit
S
SP
P7
70
06
6R
R/
/S
S/
/T
T
-
-
S
SP
P7
70
08
8R
R/
/S
S/
/
T
T
3
3.
.0
0V
V/
/3
3.
.3
3V
V
L
Lo
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P
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© 2010 Exar Corporation 10/16 Rev. 2.0.0
FEATURES
The SP706R/S/T and SP708R/S/T series
provides four
key functions:
1. A reset output during power-up, power-
down
and brownout conditions.
2. An independent watchdog output that goes
LOW if the watchdog input has not been
toggled
within 1.6 seconds.
3. A 1.25V threshold detector for power-fail
warning, low battery detection, or monitoring
a
power supply other than +3.3V/+3.0V.
4. An active-LOW manual-reset that allows
RESET to be triggered by a pushbutton switch.
The SP706R/S/T devices are the same as the
SP708R/S/T devices except for the active-
HIGH
RESET substitution of the watchdog
timer.
THEORY OF OPERATION
The SP706R/S/T-SP708R/S/T series is a
microprocessor (µP) supervisory circuit that
monitors the power supplied to digital circuits
such as microprocessors, microcontrollers, or
memory. The series is an ideal solution for
portable, battery-powered equipment that
requires power supply monitoring.
Implementing this series will reduce the
number of components and overall complexity.
The watchdog functions of this product family
will continuously oversee the operational
status of a system. The operational features
and benefits of the SP706R/S/T-SP708R/S/T
series are described in more detail below.
RESET OUTPUT
A microprocessor's reset input starts the µP in
a known state. The SP706R/S/T-SP708R/S/T
series asserts reset during power-up and
prevents code execution errors during power
down or brownout conditions.
On power-up, once V
CC
reaches 1V, RESET is a
guaranteed logic LOW of 0.4V or less. As V
CC
rises, RESET stays LOW. When V
CC
rises above
the reset threshold, an internal timer releases
RESET after 200ms. RESET pulses LOW
whenever V
CC
dips below the reset threshold,
such as in a brownout condition. When a
brownout condition occurs in the middle of a
previously initiated reset pulse, the pulse
continues for at least another 140ms. On
power down, once V
CC
falls below the reset
threshold, RESET stays LOW and is
guaranteed to be 0.4V or less until V
CC
drops
below 1V.
The active-HIGH RESET output is simply the
complement of the RESET output and is
guaranteed to be valid with V
CC
down to 1.1V.
Some µPs, such as Intel's 80C51, require an
active-HIGH reset pulse.
WATCHDOG TIMER
The SP706R/S/T-SP708R/S/T watchdog circuit
monitors the µP's activity. If the µP does not
toggle the watchdog input (WDI) within 1.6
seconds and WDI is not tri-stated, WDO goes
LOW. As long as RESET is asserted or the WDI
input is tri-stated, the watchdog timer will stay
cleared and will not count. As soon as RESET
is released and WDI is driven HIGH or LOW,
the timer will start counting. Pulses as short as
50ns can be detected.
Typically, WDO will be connected to the non-
maskable interrupt input (NMI) of a µP. When
V
CC
drops below the reset threshold, WDO will
go LOW whether or not the watchdog timer
had timed out. Normally this would trigger an
NMI but RESET goes LOW simultaneously and
thus overrides the NMI.
If WDI is left unconnected, WDO can be used
as a low-line output. Since floating WDI
disables the internal timer, WDO goes LOW
only when V
CC
falls below the reset threshold,
thus functioning as a low-line output.
Fig. 18: Watchdog Timing Waveforms
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Fig. 19: Timing Diagrams with WDI tri-stated.
P
OWER-FAIL COMPARATOR
The power-fail comparator can be used for
various purposes because its output and non
inverting input are not internally connected.
The inverting input is internally connected to a
1.25V reference.
To build an early-warning circuit for power
failure, connect the PFI pin to a voltage divider
as shown in Figure 20. Choose the voltage
divider ratio so that the voltage at PFI falls
below 1.25V just before the +5V regulator
drops out. Use PFO to interrupt the µP so it
can prepare for an orderly power-down.
Fig. 20: Typical Operating Circuit
MANUAL RESET
The manual-reset input (MR) allows RESET to
be triggered by a pushbutton switch. The
switch is effectively debounced by the 140ms
minimum RESET pulse width. MR is TTL/CMOS
logic compatible, so it can be driven by an
external logic line. MR can be used to force a
watchdog timeout to generate a RESET pulse
in the SP706R/S/T-SP708R/S/T. Simply
connect WDO to MR.
Ensuring a Valid Reset Output Down to
V
CC
=0V
When V
CC
falls below 1V, the RESET output no
longer sinks current, it becomes an open
circuit. High-impedance CMOS logic inputs can
drift to undetermined voltages if left undriven.
If a pull-down resistor is added to the RESET
pin, any stray charge or leakage currents will
be shunted to ground, holding RESET LOW.
The resistor value is not critical. It should be
about 100K, large enough not to load RESET
and small enough to pull RESET to ground.
MONITORING VOLTAGES OTHER THAN THE
UNREGULATED DC INPUT
Monitor voltages other than the unregulated
DC by connecting a voltage divider to PFI and
adjusting the ratio appropriately. If required,
add hysteresis by connecting a resistor (with a
value approximately 10 times the sum of the
two resistors in the potential divider network)
between PFI and PFO. A capacitor between PFI
and GND will reduce the power-fail circuit's
sensitivity to high-frequency noise on the line
being monitored. RESET can be used to
monitor voltages other than the +3.3V/+3.0V
V
CC
line. Connect PFO to MR to initiate a
RESET pulse when PFI drops below 1.25V.
Figure 21 shows the SP706R/S/T-SP708R/S/T
series configured to assert RESET when the
+3.3V/3.0V supply falls below the RESET
threshold, or when the +12V supply falls
below approximately 11V.
MONITORING A NEGATIVE VOLTAGE SUPPLY
The power-fail comparator can also monitor a
negative supply rail, shown in Figure 22. When
the negative rail is good (a negative voltage of
large magnitude), PFO is LOW. By adding the
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resistors and transistor as shown, a HIGH PFO
triggers RESET. As long as PFO remains HIGH,
the SP706R/S/T-SP708R/S/T series will keep
RESET asserted (where RESET = LOW and
RESET = HIGH). Note that this circuit's
accuracy depends on the PFI threshold
tolerance, the V
CC
line, and the resistors.
Fig. 21: Monitoring +3.3V/+3.0V and +12V Power
Supplies
Fig. 22: Monitoring a Negative Voltage Supply
I
NTERFACING TO µPS WITH BIDIRECTIONAL
RESET PINS
µPs with bidirectional RESET pins, such as the
Motorola 68HC11 series, can contend with the
SP705/706/707/708 RESET output. If, for
example, the RESET output is driven HIGH and
the µP wants to pull it LOW, indeterminate
logic levels may result. To correct this,
connect a 4.7K resistor between the RESET
output and the µP reset I/O, as shown if
Figure 23. Buffer the RESET output to other
system components.
Fig. 23: Interfacing to Microprocessors
with Bidirectional RESET I/O (SP706)
N
EGATIVE-GOING V
CC
TRANSIENT
While issuing resets to the μP during power-
up, power-down, and brownout conditions,
these supervisors are relatively immune to
short duration negative-going VCC transients
(glitches). It is usually undesirable to reset the
μP when V
CC
experiences only small glitches.
Figure 24 shows maximum transient duration
vs. reset-comparator overdrive, for which
reset pulses are not generated. The data was
generated using negative-going V
CC
pulses,
starting at 3.3V and ending below the reset
threshold by the magnitude indicated (reset
comparator overdrive). The graph shows the
maximum pulse width a negative-going V
CC
transient may typically have without causing a
reset pulse to be issued. As the amplitude of
the transient increases (i.e. goes farther below
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© 2010 Exar Corporation 13/16 Rev. 2.0.0
the reset threshold), the maximum allowable
pulse width decreases. Typically, a V
CC
transient that goes 100mV below the reset
threshold and lasts for 40μs or less will not
cause a reset pulse to be issued. A 100nF
bypass capacitor mounted close to the VCC pin
provides additional transient immunity.
Fig. 24: Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
APPLICATIONS
The SP706P/R/S/T-SP708R/S/T series offers
unmatched performance and the lowest power
consumption for these industry standard
devices. Refer to Figures 25 and 26 for supply
current performance characteristics rated
against temperature and supply voltages.
Fig. 25: Supply Current vs. Temperature
Fig. 26: Supply Current vs. Supply Voltage
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PACKAGE SPECIFICATION
8-PIN NSOIC
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© 2010 Exar Corporation 15/16 Rev. 2.0.0
8-PIN MSOP
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© 2010 Exar Corporation 16/16 Rev. 2.0.0
REVISION HISTORY
Revision Date Description
2.0.0 06/04/2010 Reformat of datasheet
FOR FURTHER ASSISTANCE
Email: customersupport@exar.com
Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx?
E
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design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein,
conveys no license under any patent or other right, and makes no representation that the circuits are free of patent
infringement. Charts and schedules contained herein are only for illustration purposes and may vary depending upon a
user’s specific application. While the information in this publication has been carefully checked; no responsibility, however,
is assumed for inaccuracies.
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