Micrel MIC706P μp supervisory circuit Datasheet

MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
MIC706P/R/S/T, MIC708R/S/T
µP Supervisory Circuit
General Description
Features
The MIC705, MIC706, MIC707, and MIC708 are inexpensive
mircoprocessor supervisory circuit that monitors power supplies in microprocessor based systems. The circuit functions
include a watchdog timer, microprocessor reset, backup
battery switchover, power failure warning and a debounced
manual reset input.
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
threshold level. When the supply voltage drops below the
respective reset threshold level, /RESET is asserted.
• 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
Applications
•
•
•
•
•
•
Laptop computers
Intelligent systems
Critical microprocessor power monitoring
Printers
Computers
Controllers
Ordering Information
Part Number
Temperature Range
Package
MIC70_ _NY
–40ºC to +85ºC
8-Pin PDIP
MIC70_ _MY
–40ºC to +85ºC
8-Pin SOIC
Standard
Pb-Free
MIC70_ _N
MIC70_ _M
Typical Application
+3.0 or +3.3V (Regulated)
Manual
Reset
VCC
MR RESET
VCC
RESET
MIC706
µP
I/O Line
NMI
Interrupt
WDI
WDO
PFO
DC Voltage
(Unregulated)
PFI
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
January 2006
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MIC706P/R/S/T, MIC708R/S/T
MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
Pin Configuration
MR
1
8
WDO
VCC
2
7
RESET
(RESET for MIC706P)
GND
3
6
WDI
PFI
4
5
PFO
MR
1
8
RESET
7
RESET
VCC
2
GND
3
PFI
4
MIC706
MIC708
6
NC
5
PFO
8-Pin PDIP Package
8-Pin SOIC Package
Pin Description
Pin Number
MIC705/6
Pin Number
MIC707/8
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
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
Watch Dog Input. The WDI input monitors microprcessor activity, an internal
watchdog timer resets itself with each transition on the watchdog input. If the
WDIpin is held high or low for longer than the watchog timeout period, /WDO
is forced to active low. the watchdog function can be diabled by floating the
WDI pin.
N/A
6
N/C
Not Internally Connected
7
7
/RESET
8
N/A
/WDO
N/A
8
RESET
MIC706P/R/S/T, MIC708R/S/T
Pin Function
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.
/RESET is asserted if either VCCgoes 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
Output for the Watchdog Timer. The watchdog timer resets itself with each
transition o 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 id VCC is below the reset threshold voltageand will remain low
until VCC returns to a valid level.
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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January 2006
MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
Absolute Maximum Ratings(1)
Operating Ratings(2)
Terminal Voltage
VCC ..........................................................–0.3V to +6.0V
All other inputs .............................–0.3V to (VOUT + 0.3V)
Input Current
VCC, Gnd ................................................................ 25mA
Output Current (all outputs) ........................................ 20mA
Lead Temperature (soldering, 10 sec.) ...................... 300°C
Storage Temperature ................................ –65°C to +150°C
Operating Temperature Range
MIC70_N ................................................ –40°C to +85°C
MIC70_M ................................................ –40°C to +85°C
Power Dissipation (PDIP) ........................................ 475mW
Power Dissipation (SOP) ......................................... 400mW
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
Conditions
Min.
Operating Voltage Range, VCC
Typ.
1.4
Supply Current
Reset Voltage Threshold
MIC70_P/R
MIC70_S
MIC70_T
2.55
2.85
3.00
2.63
2.93
3.08
140
200
Reset Threshold Hysteresis
Max
Units
5.5
V
30
µA
2.70
3.00
3.15
V
V
V
20
Reset Pulse Width, tRS
/RESET Output Voltage
(MIC70_R/S/T)
ISource = 200µA
ISink = 1.2mA
ISink = 50µA, VCC = 1.4V
0.8 × VCC
RESET Output Voltage
(MIC706P)
ISource = 200µA
ISink = 1.2mA
0.8 × VCC
RESET Output Voltage
(MIC708R/S/T)
ISource = 200µA
ISink = 500µA
0.8 × 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
1.6
mV
280
ms
0.3
0.3
V
V
V
0.3
V
V
0.3
V
V
2.25
sec
100
50
ns
ns
0.7 × VCC
WDI Input Current
WDI = 0V or VCC
WDO Output Voltage
ISource = 200µA
ISink = 500µA
-1
/MR Pull-Up Current
/MR = 0V
20
/MR Pulse Width, tMR
VCC = 4.5V
500
150
/MR Input Threshold
VIL
VIH
0.8 × VCC
250
0.6
V
V
1
µA
0.3
V
V
600
µA
ns
ns
0.7 × VCC
/MR to Reset Output Delay, tMD
0.6
V
V
750
ns
PFI Input Threshold
1.2
1.25
1.3
V
PFI Input Current
-25
0.01
+25
nA
0.3
V
V
/PFO Output Voltage
Note 1.
ISink = 1.2mA
ISource = 200µA
0.8 × VCC
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Specification for packaged product only.
January 2006
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MIC706P/R/S/T, MIC708R/S/T
MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
Timing Diagram
Timing Diagram for Reset
MIC706P/R/S/T, MIC708R/S/T
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January 2006
MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
Block Diagram
VCC
250•A
MR (1)
RESET
GENERATOR
+
VCC (2)
VTHR*
-
RESET (7)
(RESET for MIC706P)
WDO (8)
WATCHDOG
TIMER
WDI (6)
+
PFI (4)
1.25V
PFO (5)
-
* 2.63, 2.93, or 3.08V
MIC705/MIC706 Block diagram
•
V THR
* 2.63, 2.93, or 3.08V
MIC707/MIC708 Block Diagram
January 2006
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MIC706P/R/S/T, MIC708R/S/T
MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
Applications Information
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 with in the watchdog
timeout (Table 1.), the microprocessor is reset. /RESET will
remain asserted for 200ms when this occurs. 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 or if VCC falls
below the reset threshold as the watchdog timer is disabled
when this happens.
Microprocessor Reset
The /RESET pin is asserted whenever VCC falls below the
reset threshold voltage. The reset pin remains asserted for a
period of 200ms after VCC has risen above the reset threshold voltage. The reset timeout period can also be selected
by the end user, see Table 1. 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 and when auxiliary power is connected
to VBATT (VBATT > 2.0V), the reset pin will remain valid with
VCC from 0V to 5.5V.
Power Fail Warning
An additional comparator which is independent of the other
functions on the MIC706P/R/S/T 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 shut-down procedures prior
to power loss. Hysteresis can be added to this comparator
with external resistors, as is commonly done with any comparator. When VCC < VBATT - 1.2V (typ.), the power-fail
comparator is turned off and /PFO is pulled low in order to
conserve power.
Unregulated DC
R1
PFI
R2
+
1.25V
-
PFO
Figure 1. Power Fail Comparator
MIC706P/R/S/T, MIC708R/S/T
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January 2006
MIC706P/R/S/T, MIC708R/S/T
Micrel, Inc.
Package Information
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
0.370
0.300
0.110
0.090
8-Pin PDIP (N)
8-Pin SOIC (M)
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
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
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, Inc.
MIC706P/R/S/T, MIC708R/S/T
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January 2006