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The MIC706P/R/S/T and MIC708R/S/T are inexpensive
microprocessor supervisory circuits that monitor power
supplies in 3.0 and 3.3 Volt microprocessor based
systems. The circuit functions include a watchdog timer,
microprocessor reset, power failure warning and a
debounced manual reset input.
The MIC706 offers a watchdog timer function, while the
MIC708 has no watchdog timer but has an active high
reset output in addition to the active low reset output.
The R, S, and T versions are similar in all respects
except for supply voltage reset threshold levels. The
threshold levels are 2.63, 2.93, and 3.08V respectively.
When the supply voltage drops below the reset
threshold level, RESET (and RESET for the MIC708) is
asserted.
The MIC706P is identical to the MIC706R, except that
the Reset output is asserted high.
1
2
3
4
V
CC
GND
PFI
8
7
6
5
WDO
RESET
WDI
PFO
MIC706
MR
PFO
1
2
3
4
V
CC
GND
PFI
8
7
6
5
RESET
RESET
NC
PFO
MIC708
MR
PFO
(RESET for MIC706P)
Top View
N Package - 8 Lead Plastic DIP Package
M Package - 8 Lead Plastic SOIC Package
Part Package Temp. Range
MIC70_ _N 8-Lead PDIP -40°C to +85°C
MIC70_ _M 8-Lead SOIC -40°C to +85°C
·
Laptop Computers
·
Intelligent Instruments
·
Critical Microprocessor Power Monitoring
·
Printers
·
Computers
·
Controllers
·
30µA Maximum Supply Current
·
Debounced Manual Reset Input is
TTL/CMOS Compatible
·
Reset Pulse Width, 200ms
·
Watchdog Timer, 1.6s (MIC706)
·
Precision Supply Voltage Monitor
·
Early Power Fail Warning or Low Battery
Detect
V
CC
RESET
µP
RESET
V
CC
MIC706
+3.0 or +3.3V (Regulated)
MR
WDI
I/O Line
PFO
Interrupt
PFI
DC Voltage
(Unregulated)
Manual
Reset
WDO
NMI
Typical Operating Circuit
Features
Description Pin Configuration
Ordering Information
Typical Applications
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
MIC706P/R/S/T, MIC708R/S/T
µP Supervisory Circuits
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MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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Electrical Characteristics
VCC= 2.70V to 5.5V for MIC70_P/R, VCC= 3.00V to 5.5V for MIC70_S, VCC= 3.15V to 5.5V for MIC70_T, TA= -40°C to 85°C
unless otherwise noted.
Parameter Conditions Min Typ Max Units
Operating Voltage Range, V
CC
1.4 5.5 V
Supply Current 30 µA
Reset Voltage Threshold MIC70_P/R 2.55 2.63 2.70 V
MIC70_S 2.85 2.93 3.00
MIC70_T 3.00 3.08 3.15
Reset Threshold Hysteresis 20 mV
Reset Pulse Width, t
RS
140 200 280 ms
RESET Output Voltage I
Source
= 200µA 0.8 x
V
CC
V
(MIC70_R/S/T) I
Sink
= 1.2mA 0.3
I
Sink
= 50µA, V
CC
= 1.4V 0.3
RESET Output Voltage I
Source
= 200µA 0.8 x
V
CC
V
(MIC706P) I
Sink
= 1.2mA 0.3
RESET Output Voltage I
Source
= 200µA 0.8 x
V
CC
V
(MIC708R/S/T) I
Sink
= 500µA 0.3
Watchdog Timeout Period, t
WD
1.0 1.6 2.25 sec
WDI Minimum Input Pulse, t
WP
VIL= 0.4V, VIH= 80% of V
CC
100 ns
VIL= 0.4V, VIH= 80% of VCC>4.5V 50 ns
WDI Threshold Voltage V
IH
0.7 x V
CC
V
V
IL
0.6
WDI Input Current WDI = 0V or V
CC
-1 1 µA
WDO Output Voltage I
Source
= 200µA 0.8 x
V
CC
V
I
Sink
= 500µA 0.3
Absolute Maximum Ratings
Terminal Voltage
VCC. . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
All Other Inputs . . . . . . . . . . . . -0.3V to (VCC+ 0.3V)
Input Current
V
CC,
Gnd. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25mA
Output Current (all outputs) . . . . . . . . . . . . . . . . . 20mA
Operating Temperature Range
MIC70_N, MIC70_M . . . . . . . . . . . . . . . . . -40°C to 85°C
Storage Temperature Range . . . . . . . . . . . . .-65°C to 150°C
Lead Temperature (Soldering - 10 sec.) . . . . . . . . . . . 300°C
Power Dissipation (PDIP) . . . . . . . . . . . . . . . . . . . . 475mW
Power Dissipation (SOIC) . . . . . . . . . . . . . . . . . . . . 400mW
Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute
maximum ratings for extended periods may affect device reliability. Operating ranges define those limits between which the functionality of the device is guaranteed.
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MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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Electrical Characteristics
VCC= 2.70V to 5.5V for MIC70_P/R, VCC= 3.00V to 5.5V for MIC70_S, VCC= 3.15V to 5.5V for MIC70_T, TA= -40°C to 85°C
unless otherwise noted.
Parameter Conditions Min Typ Max Units
MR Pull-Up Current MR = 0V 20 250 600 µA
MR Pulse Width, t
MR
500 nS
VCC> 4.5V 150 nS
MR Input Threshold V
IL
0.6 V
V
IH
0.7 x
V
CC
MR to Reset Output Delay, t
MD
750 nS
PFI Input Threshold 1.2
1.25
1.3 V
PFI Input Current
-25
0.01 +25 nA
PFO Output Voltage I
Sink
= 1.2mA 0.3 V
I
Source
= 200µA 0.8 x
V
CC
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Manual Reset Input forces reset outputs to assert when
pulled below 0.8V. An internal pull-up current of 250µAon
this input forces it high when left floating. This input can
also be driven from TTL or CMOS logic.
Primary supply input, +5V.
IC ground pin, 0V reference.
Power fail input. Internally connected to the power fail
comparator which is referenced to 1.25V. The power fail
output (PFO) remains high if PFI is above 1.25V. PFI
should be connected to GND or V
OUT
if the power fail
comparator is not used.
Power fail output. The power fail comparator is
independent of all other functions on this device.
Watchdog input. The WDI input monitors microprocessor
activity, an internal watchdog timer resets itself with each
transition on the watchdog input. If the WDI pin is held high
or low for longer than the watchdog timeout period, WDO is
forced to active low. The watchdog function cannot be
disabled.
No Connect
RESET is asserted if either VCCgoes below the reset
threshold or by a low signal on the manual reset input (MR).
RESET remains asserted for one reset timeout period
(200ms) after VCCexceeds the reset threshold or after the
manual reset pin transitions from low to high. The
watchdog timer will not assert RESET unless WDO is
connected to MR.
Output for the watchdog timer. The watchdog timer resets
itself with each transition on the watchdog input. If the WDI
pin is held high or low for longer than the watchdog timeout
period, WDO is forced low. WDO will also be forced low if
VCCis below the reset threshold and will remain low until
VCCreturns to a valid level.
RESET is the compliment of RESET and is asserted if
either VCCgoes below the reset threshold or by a low
signal on the manual reset input (MR). RESET is suitable
for microprocessors systems that use an active high reset.
Pin No.
Pin Name MIC706 MIC706P MIC708
R/S/T
MR 111
VCC 222
GND 33 3
PFI 444
PFO 555
WDI 6 6 N/A
N/C N/A N/A 6
RESET 7 N/A 7
WDO 8 8 N/A
RESET N/A 7 8
Pin Functions
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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+
-
V
THR
*
RESET
GENERATOR
+
-
1.25V
WATCHDOG
TIMER
VCC(2)
MR (1)
PFO (5)
RESET (7)
WDO (8)
WDI (6)
PFI (4)
V
CC
250¥A
(RESET for MIC706P)
+
-
V
THR
*
RESET
GENERATOR
+
-
1.25V
VCC(2)
MR (1)
PFO (5)
RESET (7)
PFI (4)
V
CC
RESET (8)
250¥A
Figure 1. MIC706 Block Diagram
Figure 2. MIC708 Block Diagram
Block Diagram
* 2.63, 2.93, or 3.08V
* 2.63, 2.93, or 3.08V
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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the WDI pin will reset the watchdog timer. The output of
the watchdog timer (WDO) will remain high if WDI sees
a valid transition within the watchdog timeout period. If
VCCfalls below the reset threshold voltage then WDO
goes low immediately regardless of WDI. Likewise,
WDO goes high immediately after V
CC
exceeds the
reset threshold. WDO can be connected to MR to
generate a reset pulse upon watchdog timeout.
Microprocessor Reset
The RESET pin is asserted whenever V
CC
falls below
the reset threshold voltage or when MR goes low. The
reset pin remains asserted for a period of 200ms after
VCChas risen above the reset threshold voltage and
MR goes high. The reset function ensures the
microprocessor is properly reset and powers up into a
known condition after a power failure. RESET will
remain valid with VCCas low as 1.4V.
Power Fail Warning
An additional comparator which is independent of other
functions on the MIC706/MIC708 is provided for early
warning of power failure. An external voltage divider
can be used to compare unregulated DC to an internal
1.25V reference. The voltage divider ratio on the input
of the power fail comparator (PFI) can be chosen so as
to trip the power fail comparator a few milliseconds
before V
CC falls below the maximum reset threshold
voltage. The output of the power fail comparator (PFO)
can be used to interrupt the microprocessor when used
in this mode and execute shut-down procedures prior to
power loss.
Watchdog Timer
The microprocessor can be monitored by connecting
the WDI pin (watchdog input) to a bus line or I/O line. If
a transition doesn’t occur on the WDI pin within the
watchdog timeout period, then WDO will go low. A
minimum pulse of 50ns (4.5V supply) or 100ns (2.7V
supply) or any transition low-to-high or high-to-low on
+
-
1.25V
R1
R2
Unregulated DC
PFO
PFI
Figure 3. Power Fail Comparator
Circuit Description
Figure 4. Reset Timing Diagram
V
CC
MR
RESET
V
RT
t
MR
t
MD
t
RS
t
RS
WDO
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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MIC Direct
Industry P/N Replacement
MAX706PCPA MIC706PN
MAX706PCSA MIC706PM
MAX706PEPA MIC706PN
MAX706PESA MIC706PM
DS706PEPA MIC706PN
DS706PESA MIC706PM
MAX706RCPA MIC706RN
MAX706RCSA MIC706RM
MAX706REPA MIC706RN
MAX706RESA MIC706RM
DS706REPA MIC706RN
DS706RESA MIC706RM
MAX706SCPA MIC706SN
MAX706SCSA MIC706SM
MAX706SEPA MIC706SN
MAX706SESA MIC706SM
DS706SEPA MIC706SN
DS706SESA MIC706SM
MAX706TCPA MIC706TN
MAX706TCSA MIC706TM
MAX706TEPA MIC706TN
MAX706TESA MIC706TM
DS706TEPA MIC706TN
DS706TESA MIC706TM
MAX708RCPA MIC708RN
MAX708RCSA MIC708RM
MAX708REPA MIC708RN
MAX708RESA MIC708RM
DS708REPA MIC708RN
DS708RESA MIC708RM
MAX708SCPA MIC708SN
MAX708SCSA MIC708SM
MAX708SEPA MIC708SN
MAX708SESA MIC708SM
DS708SEPA MIC708SN
DS708SESA MIC708SM
MAX708TCPA MIC708TN
MAX708TCSA MIC708TM
MAX708TEPA MIC708TN
MAX708TESA MIC708TM
DS708TEPA MIC708TN
DS708TESA MIC708TM
Alternate Source Cross Reference Guide
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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Packaging Information
0.244
0.228
0.155
0.150
0.197
0.190
0.019
0.013
0.060
0.040
0.069
0.053
0.011
0.004
0.012
0.009
0.050
0.016
0-8¼
Pin 1 Identifier
0.260
0.240
0.400
0.370
0.023
0.015
0.110
0.090
0.150
0.120
0.150
0.125
0.035
0.015
0.370
0.300
0.310
0.290
M Package, 8-Pin Small Outline
N Package, 8-Pin Plastic Dual-In-Line
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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