Micrel MIC705 μp supervisory circuit Datasheet

MIC705/706/707/708
µP Supervisory Circuit
General Description
Features
The MIC705, MIC706, MIC707, and MIC708 are
inexpensive microprocessor supervisory circuits that
monitor power supplies in microprocessor-based systems.
The circuit functions include a watchdog timer,
microprocessor reset, power-failure warning, and a
debounced manual reset input.
• Debounced manual reset input is TTL/CMOS
compatible
• Reset pulse width: 200ms
• Watchdog timer: 1.6s (MIC705/706)
• 4.65V or 4.40V precision voltage monitor
• Early power-fail warning or low-battery detect
The MIC705 and MIC706 offer a watchdog timer function
while the MIC707 and MIC708 have an active-high reset
output in addition to the active-low reset output.
Supply voltage monitor levels of 4.65V and 4.4V are
available. The MIC705 and MIC707 have a nominal reset
threshold level of 4.65V while the MIC706 and MIC708
have a 4.4V nominal reset threshold level. When the
supply voltage drops below the respective reset threshold
level, /RESET is asserted.
Applications
•
•
•
•
•
•
Automotive systems
Intelligent systems
Critical microprocessor power monitoring
Battery-powered computers
Computers
Controllers
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Typical Application
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 15, 2014
Revision 2.1
Micrel, Inc.
MIC705/706/707/708
Ordering Information
Part Number
Threshold (V)
/RESET
MIC705MY
4.65
MIC706MY
RESET
WDI
Junction Temperature Range
Package
√
√
−40°C to +85°C
8-Pin SOIC
4.40
√
√
−40°C to +85°C
8-Pin SOIC
MIC707MY
4.65
√
√
−40°C to +85°C
8-Pin SOIC
MIC708MY
4.40
√
√
−40°C to +85°C
8-Pin SOIC
Pin Configuration
MIC705/706
8-Pin SOIC (M)
(Top View)
MIC707/708
8-Pin SOIC (M)
(Top View)
Pin Description
Pin Number
MIC706
Pin Number
MIC708
Pin Name
1
1
/MR
Manual reset input forces /RESET 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.
2
2
VCC
Primary supply input, +5V.
3
3
GND
IC ground pin, 0V reference.
Pin Name
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 VCC if the power-fail comparator is not
used.
4
4
PFI
5
5
/PFO
Power-Fail Output: The power-fail comparator is independent of all other function
on this device.
6
N/A
WDI
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 can be disabled by floating the WDI pin.
N/A
6
N/C
Not internally connected.
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MIC705/706/707/708
Pin Description (Continued)
Pin Number
MIC706
Pin Number
MIC708
7
7
Pin Name
Pin Name
/RESET
/RESET is asserted if either VCC goes below the reset threshold voltage or by low
signal on the manual reset input (/MR). /RESET remains asserted for one reset
timeout period (200ms) after VCC exceeds the reset threshold voltage or after the
manual reset pin transition from low to high. The watchdog timer will not assert
/RESET unless /WDO is connected to /MR.
8
N/A
/WDO
Output for the watchdog timer. The watchdog timer resets itself with each transition
to 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 voltage and will remain low until VCC returns to a valid
level.
N/A
8
RESET
RESET is the compliment of /RESET and is asserted if either VCC goes below the
reset threshold voltage or by a low signal on the manual reset input (/MR). RESET
is suitable for microprocessor systems that use active high reset.
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Micrel, Inc.
MIC705/706/707/708
Absolute Maximum Ratings(1)
Operating Ratings(2)
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) ..................................................... 20mA
Lead Temperature (soldering, 10s) ............................ 300°C
Storage Temperature (TS) ......................... −65°C to +150°C
Operating Temperature Range ................... –40°C to +85°C
Power Dissipation (SOP) ......................................... 400mW
Thermal Resistance
8-Pin SOIC....................................................... 150°C/W
Electrical Characteristics(3)
VCC = 4.75V to 5.5V for MIC705/707; VCC = 4.5V to 5.5V for MIC706/708; TA = Operating Temperature Range,
bold values indicate –40°C ≤ TA ≤ +85°C, unless noted.
Parameter
Condition
Min.
Operating Voltage Range
Typ.
1.4
Supply Current
Reset Voltage Threshold
WDI Threshold Voltage
WDI Input Current
WDO Output Voltage
/MR Pull-Up Current
V
60
µA
4.65
4.75
MIC706, MIC708
4.25
4.4
4.5
40
140
200
ISINK = 3.2mA
280
0.4
VCC − 1.5V
ISOURCE = 800µA
ISINK = 1.2mA
0.4
1.0
VIL = 0.4V, VIH = 80% of VCC
50
VIH, VCC = 5V
3.5
1.6
2.25
0.8
−150
WDI = VCC
−50
50
150
VCC − 1.5V
ISOURCE = 800µA
ISINK = 1.2mA
0.4
/MR = 0V
100
ms
V
V
s
ns
VIL, VCC = 5V
WDI = 0V
V
mV
VCC − 1.5V
ISOURCE = 800µA
Watchdog Timeout Period (tWD)
WDI Minimum Input Pulse (tWP)
5.5
4.50
Reset Pulse Width (tRS)
RESET Output Voltage
Units
MIC705, MIC707
Reset Threshold Hysteresis
/RESET Output Voltage
Max.
250
600
V
µA
V
µA
Notes:
1. Exceeding the absolute maximum ratings may damage the device.
2. The device is not guaranteed to function outside its operating ratings.
3. Specification for packaged product only
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MIC705/706/707/708
Electrical Characteristics(3) (Continued)
VCC = 4.75V to 5.5V for MIC705/707; VCC = 4.5V to 5.5V for MIC706/708; TA = Operating Temperature Range,
bold values indicate –40°C ≤ TA ≤ +85°C, unless noted.
Parameter
Condition
Min.
/MR Pulse Width (tMR)
/MR Input Threshold
Typ.
150
VIL
0.8
VIH
2.0
VCC = 5V
PFI Input Current
/PFO Output Voltage
September 15, 2014
250
ns
1.25
1.3
V
−25
0.01
+25
nA
0.4
5
V
1.2
ISINK = 3.2mA
VCC = 5V, ISOURCE = 800µA
Units
ns
/MR-to-Reset Output Delay (tMD)
PFI Input Threshold
Max.
VCC − 1.5V
V
Revision 2.1
Micrel, Inc.
MIC705/706/707/708
Timing Diagram
Figure 1. Timing Diagram for Reset
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Micrel, Inc.
MIC705/706/707/708
Block Diagrams
MIC705/MIC706 Block Diagram
MIC707/MIC708 Block Diagram
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MIC705/706/707/708
Application Information
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 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.
Watchdog Timer
The microprocessor can be monitored by connecting the
WDI pin (watchdog input) to a bus line or an 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 or any transition low-to-high or
high-to-low on the WDI pin will reset the watchdog timer.
The output of the watchdog timer (/WDO) will remain high
if WDI left floating. If VCC falls below the reset threshold
voltage, then /WDO goes low immediately regardless of
WDI.
Power-Fail Warning
An additional comparator which is independent of the
other functions on the MIC706/706/707/708 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 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 shutdown procedures prior to
power loss. Hysteresis can be added to this comparator
with external resistors, as is commonly done with any
comparator.
Figure 2. Power-Fail Comparator
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MIC705/706/707/708
Package Information and Recommended Landing Pattern(4)
8-Pin SOIC (M)
Note:
4. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.
September 15, 2014
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Micrel, Inc.
MIC705/706/707/708
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel, Inc. is a leading global manufacturer of IC solutions for the worldwide high performance linear and power, LAN, and timing & communications
markets. The Company’s products include advanced mixed-signal, analog & power semiconductors; high-performance communication, clock
management, MEMs-based clock oscillators & crystal-less clock generators, Ethernet switches, and physical layer transceiver ICs. Company
customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunications, automotive, and computer products.
Corporation headquarters and state-of-the-art wafer fabrication facilities are located in San Jose, CA, with regional sales and support offices and
advanced technology design centers situated throughout the Americas, Europe, and Asia. Additionally, the Company maintains an extensive network
of distributors and reps worldwide.
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this datasheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
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