Micrel MIC70 M μp supervisory circuit Datasheet

MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
MIC706P/R/S/T, MIC708R/S/T
µP Supervisory Circuits
Description
Pin Configuration
Top View
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.
· Laptop Computers
· Intelligent Instruments
· Critical Microprocessor Power Monitoring
· Printers
· Computers
· Controllers
8
2
7
WDO
RESET
(RESET for MIC706P)
GND
3
6
WDI
PFI
4
5
PFO
N Package - 8 Lead Plastic DIP Package
M Package - 8 Lead Plastic SOIC Package
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.
Typical Applications
1
MIC706
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 MIC706P is identical to the MIC706R, except that
the Reset output is asserted high.
MR
VCC
MR
1
8
RESET
VCC
2
7
RESET
GND
3
6
NC
PFI
4
5
PFO
MIC708
Features
· 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
Typical Operating Circuit
+3.0 or +3.3V (Regulated)
Ordering Information
Part
MIC70_ _N
MIC70_ _M
Package
8-Lead PDIP
8-Lead SOIC
Temp. Range
-40°C to +85°C
-40°C to +85°C
Manual
Reset
VCC
VCC
MR
RESET
RESET
MIC706
WDI
DC Voltage
(Unregulated)
WDO
PFI
PFO
µP
I/O Line
NMI
Interrupt
1
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
Absolute Maximum Ratings
Terminal Voltage
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
All Other Inputs . . . . . . . . . . . . -0.3V to (VCC + 0.3V)
Input Current
VCC, 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.
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
Operating Voltage Range, VCC
Min
Typ
1.4
Supply Current
Reset Voltage Threshold
MIC70_P/R
MIC70_S
MIC70_T
2.55
2.85
3.00
Reset Threshold Hysteresis
Units
5.5
V
30
µA
2.70
3.00
3.15
V
20
Reset Pulse Width, tRS
140
RESET Output Voltage
(MIC70_R/S/T)
ISource = 200µA
ISink = 1.2mA
ISink = 50µA, VCC = 1.4V
0.8 x VCC
RESET Output Voltage
(MIC706P)
ISource = 200µA
ISink = 1.2mA
0.8 x VCC
RESET Output Voltage
(MIC708R/S/T)
ISource = 200µA
ISink = 500µA
0.8 x VCC
Watchdog Timeout Period, tWD
1.0
WDI Minimum Input Pulse, tWP
VIL = 0.4V, VIH = 80% of VCC
VIL = 0.4V, VIH = 80% of VCC>4.5V
WDI Threshold Voltage
VIH
VIL
200
mV
280
0.7 x VCC
WDI = 0V or VCC
-1
WDO Output Voltage
ISource = 200µA
ISink = 500µA
0.8 x VCC
ms
V
0.3
0.3
V
0.3
V
0.3
1.6
2.25
100
50
WDI Input Current
2
2.63
2.93
3.08
Max
sec
ns
ns
V
0.6
1
µA
V
0.3
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
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
MR Pull-Up Current
MR Pulse Width, tMR
MR Input Threshold
Min
Typ
Max
Units
MR = 0V
20
250
600
µA
VCC > 4.5V
500
150
VIL
VIH
nS
nS
0.6
V
750
nS
0.7 x VCC
MR to Reset Output Delay, tMD
PFI Input Threshold
1.2
1.25
1.3
V
PFI Input Current
-25
0.01
+25
nA
0.3
V
PFO Output Voltage
ISink = 1.2mA
ISource = 200µA
0.8 x VCC
3
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
Pin Functions
Pin No.
Pin Name
MIC706
R/S/T
MIC706P
MIC708
MR
1
1
1
Manual Reset Input forces reset outputs to assert when
pulled below 0.8V. An internal pull-up current of 250µA on
this input forces it high when left floating. This input can
also be driven from TTL or CMOS logic.
VCC
2
2
2
Primary supply input, +5V.
GND
3
3
3
IC ground pin, 0V reference.
PFI
4
4
4
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.
PFO
5
5
5
Power fail output. The power fail comparator is
independent of all other functions on this device.
WDI
6
6
N/A
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.
N/C
N/A
N/A
6
No Connect
RESET
7
N/A
7
RESET is asserted if either V CC goes 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 VCC exceeds 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.
WDO
8
8
N/A
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
VCC is below the reset threshold and will remain low until
VCC returns to a valid level.
N/A
7
8
RESET is the compliment of RESET and is asserted if
either V CC goes 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.
RESET
4
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
Block Diagram
VCC
250¥A
MR (1)
RESET
+
VCC (2)
GENERATOR
RESET (7)
(RESET for MIC706P)
-
VTHR *
WDO (8)
WATCHDOG
WDI (6)
TIMER
+
PFI (4)
PFO (5)
-
1.25V
* 2.63, 2.93, or 3.08V
Figure 1. MIC706 Block Diagram
VCC
250¥A
RESET (8)
MR (1)
RESET
+
VCC (2)
VTHR*
GENERATOR
RESET (7)
-
+
PFI (4)
PFO (5)
1.25V
-
* 2.63, 2.93, or 3.08V
Figure 2. MIC708 Block Diagram
5
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
Circuit Description
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
Unregulated DC
R1
PFI
+
R2
1.25V
-
PFO
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
VCC falls below the reset threshold voltage then WDO
goes low immediately regardless of WDI. Likewise,
WDO goes high immediately after VCC 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 VCC falls below
the reset threshold voltage or when MR goes low. The
reset pin remains asserted for a period of 200ms after
VCC
VRT
Figure 3. Power Fail Comparator
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 VCC 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
6
tMR
MR
tMD
tRS
tRS
RESET
WDO
Figure 4. Reset Timing Diagram
VCC has 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 VCC as low as 1.4V.
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
Alternate Source Cross Reference Guide
Industry P/N
MAX706PCPA
MAX706PCSA
MAX706PEPA
MAX706PESA
DS706PEPA
DS706PESA
MAX706RCPA
MAX706RCSA
MAX706REPA
MAX706RESA
DS706REPA
DS706RESA
MAX706SCPA
MAX706SCSA
MAX706SEPA
MAX706SESA
DS706SEPA
DS706SESA
MAX706TCPA
MAX706TCSA
MAX706TEPA
MAX706TESA
DS706TEPA
DS706TESA
MAX708RCPA
MAX708RCSA
MAX708REPA
MAX708RESA
DS708REPA
DS708RESA
MAX708SCPA
MAX708SCSA
MAX708SEPA
MAX708SESA
DS708SEPA
DS708SESA
MAX708TCPA
MAX708TCSA
MAX708TEPA
MAX708TESA
DS708TEPA
DS708TESA
MIC Direct
Replacement
MIC706PN
MIC706PM
MIC706PN
MIC706PM
MIC706PN
MIC706PM
MIC706RN
MIC706RM
MIC706RN
MIC706RM
MIC706RN
MIC706RM
MIC706SN
MIC706SM
MIC706SN
MIC706SM
MIC706SN
MIC706SM
MIC706TN
MIC706TM
MIC706TN
MIC706TM
MIC706TN
MIC706TM
MIC708RN
MIC708RM
MIC708RN
MIC708RM
MIC708RN
MIC708RM
MIC708SN
MIC708SM
MIC708SN
MIC708SM
MIC708SN
MIC708SM
MIC708TN
MIC708TM
MIC708TN
MIC708TM
MIC708TN
MIC708TM
7
MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuits
Packaging Information
M Package, 8-Pin Small Outline
0.197
0.190
Pin 1 Identifier
0.155
0.244
0.150
0.228
0.012
0.069
0.009
0.053
0-8¼
0.060
0.019
0.040
0.050
0.011
0.016
0.004
0.013
N Package, 8-Pin Plastic Dual-In-Line
0.400
0.370
0.260
0.240
0.310
0.290
0.150
0.120
0.035
0.015
0.150
0.125
0.023
0.015
8
0.110
0.090
0.370
0.300