MIC706P/R/S/T, MIC708R/S/T General Description Features µP Supervisory Circuit

MIC706P/R/S/T, MIC708R/S/T General Description Features µP Supervisory Circuit
MIC706P/R/S/T, MIC708R/S/T
µP Supervisory Circuit
General Description
Features
The MIC706 and MIC708 are inexpensive microprocessor
supervisory circuits that monitor power supplies in 3.0V
and 3.3V microprocessor-based systems. The circuit
functions include a watchdog timer, microprocessor reset,
power-failure warning, and a debounced manual reset
input.
• Maximum supply current: 30µA
• Debounced manual reset input is TTL/CMOS
compatible
• Reset pulse width: 200ms
• Watchdog timer: 1.6s (MIC706)
• Precision supply voltage monitor
• Easy power-fail warning or low-battery detect
The MIC706 offers a watchdog timer function, while the
MIC708 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.
Applications
•
•
•
•
•
Laptop and desktop computers
Intelligent systems
Critical microprocessor power monitoring
Printers
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
May 28, 2014
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Ordering Information
Part Number
Threshold (V)
MIC706PMY
2.63
MIC706RMY
2.63
MIC706SMY
/RESET
RESET
WDI
Junction Temperature Range
Package
√
√
–40°C to +85°C
8-Pin SOIC
√
√
–40°C to +85°C
8-Pin SOIC
2.93
√
√
–40°C to +85°C
8-Pin SOIC
MIC706TMY
3.08
√
√
–40°C to +85°C
8-Pin SOIC
MIC708RMY
2.63
√
√
–40°C to +85°C
8-Pin SOIC
MIC708SMY
2.93
√
√
–40°C to +85°C
8-Pin SOIC
MIC708TMY
3.08
√
√
–40°C to +85°C
8-Pin SOIC
Pin Configuration
MIC706
8-Pin SOIC (M)
(Top View)
MIC708
8-Pin SOIC (M)
(Top View)
Pin Description
Pin Number
MIC706
Pin Number
MIC708
Pin Name
1
1
/MR
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.
2
2
VCC
Primary supply input, +5V.
3
3
GND
IC ground pin, 0V reference.
4
4
PFI
5
5
/PFO
Power-Fail Output: The power-fail comparator is independent of all other function
on this device.
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 VOUT if the power-fail comparator is not
used.
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.
May 28, 2014
2
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Pin Description (Continued)
Pin Number
MIC706
7
Pin Number
MIC708
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.
7
(MIC706P)
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.
May 28, 2014
3
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
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 = 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 = 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
30
µA
2.70
MIC70_S
2.85
2.93
3.00
MIC70_T
3.00
3.08
3.15
20
140
200
V
mV
280
ms
ISINK = 1.2mA
0.3
V
ISINK = 50µA, VCC = 1.4V
0.3
0.8 × VCC
ISOURCE = 200µA
0.8 × VCC
ISINK = 1.2mA
0.3
ISOURCE = 200µA
0.8 × VCC
ISINK = 500µA
0.3
Watchdog Timeout Period (tWD)
WDI Minimum Input Pulse (tWP)
V
2.63
ISOURCE = 200µA
RESET Output Voltage (MIC708R/S/T)
5.5
2.55
Reset Pulse Width (tRS)
RESET Output Voltage (MIC706P)
Units
MIC70_P/R
Reset Threshold Hysteresis
/RESET Output Voltage (MIC70_R/S/T)
Max.
1.0
VIL = 0.4V, VIH = 80% of VCC
100
VIL = 0.4V, VIH = 80% of VCC > 4.5V
50
VIH
1.6
2.25
VIL
0.6
−1
ISOURCE = 200µA
0.8 × VCC
1
ISINK = 500µA
0.3
/MR = 0V
20
V
s
ns
0.7 × VCC
WDI = 0V or VCC
V
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.
May 28, 2014
4
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Electrical Characteristics(3) (Continued)
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 = Operating Temperature Range, bold values indicate –40°C ≤ TA ≤ +85°C, unless noted.
Parameter
Condition
/MR Pulse Width (tMR)
VCC > 4.5V
/MR Input Threshold
Min.
Typ.
Max.
500
ns
150
VIL
0.6
VIH
Units
0.7 × VCC
/MR-to-Reset Output Delay (tMD)
V
750
ns
PFI Input Threshold
1.2
1.25
1.3
V
PFI Input Current
−25
0.01
+25
nA
/PFO Output Voltage
May 28, 2014
ISINK = 1.2mA
0.3
ISOURCE = 200µA
0.8 × VCC
5
V
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Timing Diagram
Figure 1. Timing Diagram for Reset
May 28, 2014
6
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Block Diagram
MIC706 Block Diagram
MIC708 Block Diagram
May 28, 2014
7
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
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 in the
watchdog timeout period, then /WDO will go low. A
minimum pulse of 100ns 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 sees a valid transition within the watchdog period.
If VCC falls below the reset threshold voltage, then /WDO
goes low immediately regardless of WDI. /WDO can be
connected to /MR to generate a reset pulse upon
watchdog timeout.
Application Information
An additional comparator which is independent of the
other functions on the MIC706P and 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 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.
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.
Figure 2. Power-Fail Comparator
May 28, 2014
8
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
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.
May 28, 2014
9
Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
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 makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. 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
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2000 Micrel, Incorporated.
May 28, 2014
10
Revision 2.0
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising