UM706TS [UNIONSEMI]
Supply Voltage Supervisor w/Watchdog Input and Manual Reset;
| 型号： | UM706TS |
| 厂家： | 
Union Semiconductor, Inc. |
| 描述： | Supply Voltage Supervisor w/Watchdog Input and Manual Reset |
| 文件： | 总15页 (文件大小：558K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Supply Voltage Supervisor w/Watchdog Input and Manual Reset
UM706xS SOP8
UM708xS SOP8
General Description
The UM706xS/UM708xS series are cost effective system power supply supervisory circuits
designed to monitor the power supplies in digital systems.
The UM706xS provides power-supply monitoring circuitry that generates a reset output during
power-up, power-down, and brownout conditions. The reset output remains operational with VCC
as low as 1V. Independent watchdog monitoring circuitry is also provided. This is activated if the
watchdog input has not been toggled within 1.6 seconds. In addition, there is a 1.25V threshold
detector for power-fail warning, low battery detection, or to monitor an additional power supply.
An active low debounced manual reset input is also included.
The UM708xS is the same as the UM706xS, except an active-high reset is substituted for the
watchdog timer. All parts are available in a small outline SOP8 package.
Applications
Features
Applications using DSPs, Microcontrollers Wide Operation Voltage Range of 1V to 5.5V
or Microprocessors
Programmable Controls
Computers
Correct Logic Output Guaranteed to
VCC=1.0V
Precision Supply-Voltage Monitor: 2.63V,
2.93V, 3.08V,4.38V,4.63V
Embedded System
200ms Reset Pulse Width
Independent Watchdog Timer-1.6s Timeout
(UM706xS)
Active-high Reset Output (UM708xS)
Voltage Monitor for Power-Fail or
Low-Battery Warning
Industrial Equipments
Intelligent Instrument
Wireless Communications Systems
Temperature Range: -40°C to +85°C
Supply Current of 80μA (Typ.)
Pin Configurations
Top View
8
7
6
5
1
2
3
4
8
7
6
5
MR
VCC
WDO(RESET)*
UM706(708)*
RESET
XS
XX
GND
PFI
WDI(NC)*
PFO
1
2
3
4
XX: Week Code
( )* for UM708xS
UM706xS
( )* for UM708xS
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Ordering Information
Top
RESET
Threshold (V)
4.63
Timeout Period
Package Type
(ms)
Part Number
Marking
UM706LS
UM706MS
UM706TS
UM706SS
UM706RS
UM708LS
UM708MS
UM708TS
UM708SS
UM708RS
UM706LS
UM706MS
UM706TS
UM706SS
UM706RS
UM708LS
UM708MS
UM708TS
UM708SS
UM708RS
240
240
240
240
4.38
3.08
2.93
2.63
4.63
4.38
3.08
2.93
240
SOP8
240
240
240
240
240
2.63
Typical Application Circuit
Vcc
μP
Vcc
RESET
Vcc
RESET
I/O
WDI
WDO
PFO
UM706
PFI
NMI
MR
INT
PUSHBUTTON
SWITCH
Figure 1. UM706xS Application Circuit
Vcc
μP
Vcc
RESET
RESET
RESET
Vcc
RESET
UM708
PFI
MR
PFO
INT
PUSHBUTTON
SWITCH
Figure 2. UM708xS Application Circuit
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Pin Description
Pin
Number
Pin Name
Function
Manual-Reset Input triggers a reset pulse when pulled below
0.8V. This active-low input has an internal 250μA pull-up
current. It can be driven from a TTL or CMOS logic line as
well as shorted to ground with a switch.
_______
1
MR
2
3
VCC
Supply Input
GND
Ground Reference for all signals.
Power-Fail Voltage Monitor Input. When PFI is less than
________
4
5
PFI
1.25V, PFO goes low. Connect PFI to GND or VCC when
not used.
Power-Fail Output goes low and sinks current when PFI is
________
________
PFO
less than 1.25V; otherwise PFO stays high.
Watchdog Input. If WDI remains either high or low for
__________
longer than the watchdog timeout period, the WDO goes
low. The timer resets with each transition at the WDI input.
Either a high-to-low or a low-to-high transition clears the
counter. The internal timer is also cleared whenever reset is
asserted.
UM706
WDI
6
7
UM708
NC
No Connect
Active-Low Reset Output pulses low for 200ms when
trigged, and stays low whenever VCC is below the reset
______________
RESET
threshold. It remains low for 200ms after VCC rises above the
_______
reset threshold or MR goes from Low to High.
Watchdog Output pulls low when the internal watchdog timer
finishes its 1.6sec count and does not go high again until the
___________
watchdog is cleared. WDO also goes low during low-line
conditions. Whenever VCC is below the reset threshold,
___________
UM706
UM708
WDO
___________
______________
___________
WDO stays low; however, unlike RESET, WDO does not
8
have a minimum pulse width. As soon as VCC rises above the
___________
reset threshold, WDO goes high with no delay.
____________
Active-High Reset Output is the inverse of RESET .
RESET
____________
Whenever RESET is high, RESET is low, and vice versa.
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Absolute Maximum Ratings (Note 1)
Symbol
Parameter
Value
-0.3 to +6.0
-0.3 to VCC +0.3
20
Unit
V
VCC
Supply Voltage
____________
V
RESET, RESET (push-pull)
Input Current, VCC
ICC
IO
mA
mA
V/μs
mW
°C
____________
20
Output Current, RESET, RESET
Rate of Rise, VCC
100
PD
TJ
Continuous Power Dissipation
Operating Junction Temperature
Storage Temperature Range
471
-40 to +105
-65 to +150
300
TSTG
°C
Lead Temperature (soldering, 10s)
°C
Note 1: Stresses beyond those listed under “Absolute maximum Ratings” may cause permanent
damage to the device.
Electrical Characteristics
VCC = full range, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA =+25°C,
VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, and VCC = 3V for R version. (Note 2)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
TA=0℃ to + 70℃
1.0
1.2
5.5
5.5
VCC
VCC Range
V
TA=-40℃ to + 85℃
Supply
Current
ICC
μA
TA=-40℃ to + 85℃
150
80
TA=+25℃
TA=-40℃ to + 85℃
TA=+25℃
4.56
4.50
4.31
4.63
4.70
4.75
4.45
UM706L/
UM708L
4.38
UM706M/
UM708M
TA=-40℃ to + 85℃
TA=+25℃
TA=-40℃ to + 85℃
TA=+25℃
TA=-40℃ to + 85℃
TA=+25℃
4.25
3.04
3.00
2.89
2.85
2.59
4.50
3.11
3.15
2.96
3.00
2.66
Reset
Threshold
3.08
2.93
UM706T/
UM708T
VTH
V
UM706S/
UM708S
2.63
UM706R/
UM708R
TA=-40℃ to + 85℃
2.55
2.70
Reset
Threshold
Hysteresis
40
mV
ms
Reset Pulse
Width
tRS
140
200
280
Note 2: Production testing done at TA = +25°C; limits over temperature guaranteed by design
only.
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Electrical Characteristics (Continued)
VCC = full range, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA =+25°C,
VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, and VCC = 3V for R version. (Note 2)
Symbol
Parameter
Conditions
Min.
Typ. Max.
Unit
ISINK=1.2mA,
(for R/S/T versions)
ISINK=3.2mA,
0.3
0.4
0.3
______________
RESET /RESET
Output Voltage Low
VOL
V
V
(for L/M versions)
VCC = 1.2V,
ISINK = 100µA
RESET/ RESET
Output Voltage High
VOH
ISOURCE = 800µA
MR=0V
VCC-1.5
MR Pull-Up Current
100
150
µA
ns
250
600
0.8
tMR
MR Pulse Width
_______
MR Input Threshold,
V
V
Low
_______
MR Input Threshold,
2.0
High
tMD
MR to Reset Out Delay
PFI Input Threshold
PFI Input Current
ns
V
250
1.30
+25
VCC=5V
1.20
-25
1.25
0.01
nA
________
ISOURCE=800µA
ISINK=3.2mA
Vcc-1.5
PFO Output Voltage
V
0.4
Watchdog function for UM706
Watchdog Timeout
tWD
1.0
50
s
1.6
2.25
Period
tWP
WDI Pulse Width
WDI Input Threshold
Low
VIL=0.4V,VIH=0.8Vcc
VCC=5V
ns
V
0.8
WDI Input Threshold
VCC=5V
3.5
V
High
WDI=VCC
WDI=0V
50
150
WDI Input Current
µA
-150
-50
WDO Output Voltage
High
ISOURCE=800µA
ISINK=1.2mA
Vcc-1.5
V
V
WDO Output Voltage
0.4
Low
Note 2: Production testing done at TA = +25°C; limits over temperature guaranteed by design
only.
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Block Diagram
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
WDI
6
8
WDO
TIMEBASE FOR
RESET AND
WATCHDOG
VCC
250μA
1
2
MR
RESET
GENERATOR
7
RESET
VCC
+
-
VREF
PFI
4
+
-
5
PFO
1.25V
3
GND
Figure 3. UM706xS Block Diagram
8
RESET
RESET
VCC
250μA
1
2
MR
RESET
GENERATOR
7
VCC
+
-
VREF
PFI
4
+
5
PFO
-
1.25V
3
GND
Figure 4. UM708xS Block Diagram
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Typical Operating Characteristics
______________
______________
RESET Output Voltage vs. Supply Voltage
RESET Response Time
(a)
(b)
2V/div
VCC
VCC
2V/div
2V/div
_____________
RESET
2V/div
_____________
RESET
500ms/div
1μs/div
Power-fail Comparator Assertion
Response Time
Power-fail Comparator De-assertion
Response Time
(c)
(d)
2V/div
_________
PFO
2V/div
_________
PFO
1V/div
1V/div
PFI
PFI
200ns/div
200ns/div
2kΩ
10kΩ
VCC
VCC
VCC
VCC
RESET
RESET
RESET
RESET
330pF
30pF
GND
GND
(a)
(b)
+5V
1kΩ
+5V
PFI
+
-
PFO
PFI
+
-
PFO
30pF
1kΩ
30pF
+1.25V
+1.25V
(c)
(d)
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Typical Operating Characteristics
RESET Output Voltage vs. Supply Voltage
RESET Response Time
(e)
(e)
2V/div
2V/div
VCC
VCC
2V/div
2V/div
2V/div
RESET
RESET
RESET
500ms/div
2μs/div
______________
______________
RESET, RESET Assertion
RESET, RESET De-assertion
(f)
(f)
2V/div
2V/div
RESET
______________
RESET
_____________
2V/div
RESET
200ns/div
200ns/div
VCC
VCC
10kΩ
RESET
RESET
RESET
10kΩ
330pF
10kΩ
330pF
GND
330pF
GND
(e)
(f)
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Detailed Description
Power-Fail Reset
The reset output provides a reset signal to the microprocessor whenever the VCC input is below the
threshold. An internal timer holds the reset output active for 200ms after the voltage on VCC rises
above the threshold. This is intended as a power-on reset signal for the microprocessor. It allows
time for both the power supply and the microprocessor to stabilize after power-up. If a power
supply brownout or interruption occurs, the reset line is similarly activated and remains active for
200ms after the supply recovers. If another interruption occurs during an active reset period, the
reset timeout period continues for an additional 200ms.
The reset output is guaranteed to remain valid with VCC as low as 1V. This ensures that the
microprocessor is held in a stable shutdown condition as the power supply starts up.
______________
The UM706xS provides an active low RESET signal while the UM708xS provides an active
______________
high RESET signal as well as active low RESET signal.
Power-Fail Comparator
The power-fail comparator can be used for various purposes because its output and non-inverting
input are not internally connected. The inverting input is internally connected to a 1.25V
reference.
To build an early-warning circuit for power failure, connect the PFI pin to a voltage driver, choose
the voltage divider ratio so that the voltage at PFI falls below 1.25V just before the regulator drops
________
out. Use PFO to interrupt the µP so it can prepare for an orderly power-down.
Manual Reset
_______
The Manual-Reset input (MR) allows reset to be trigged by a pushbutton switch. The switch is
_______
effectively debounced by the 140ms minimum reset pulse width. MR is TTL/CMOS logic
_______
compatible, so it can be driven by an external logic line. If unused, MR input can be tied high or
left floating.
Watchdog Timer
The UM706xS watchdog timer circuit is used to monitor the activity of the microprocessor to
check that it is not stalled in an indefinite loop. An output line on the processor is used to toggle
__________
__________
the watchdog input (WDI). If this line is not toggled within 1.6sec, WDO goes low. WDO is
connected to the non-maskable interrupt input (NMI) of a μP. Therefore, if the watchdog timer
times out, an interrupt is generated. The interrupt service routine is used to rectify the problem.
The watchdog timer is cleared either by a high-to-low or by a low-to-high transition on WDI.
_____________
Pulses as narrow as 50ns are detected. The timer is also cleared by RESET/RESET going active.
Therefore, the watchdog timeout period begins after reset goes inactive.
__________
When VCC falls below the reset threshold, WDO is forced low whether or not the watchdog timer
_____________
has timed out. Normally, this generates an interrupt, but it is overridden by RESET/RESET going
active.
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tWP
tWD
tWD
tWD
+5V
0V
WDI
+5V
WDO
0V
+5V
RESET
RESET EXTERNALLY
TRIGGERED BY MR
0V
tRS
Figure 5. Watchdog and Reset Timing
VCC
+5V
VRT
VRT
tRS
tRS
RESET
MR
0V
+5V
0V
tMD
tMR
+5V
WDO
MR EXTERNALLY DRIVEN LOW
0V
Figure 6. Reset, Manual Reset and Watchdog Timing
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Applications Information
______________
Valid RESET below 1V VCC
The UM706xS/UM708xS are guaranteed to provide a valid reset level with VCC as low as 1V.
When VCC falls below 1V, the internal transistor does not have sufficient drive to hold it on so the
_____________
_____________
voltage on RESET is no longer held at 0V. If a pull-down resistor is added to the RESET pin
as shown in Figure 7, any stray charge or leakage current will be drained to ground, holding
_____________
RESET low. Resistor value (R1) is not critical. It should be about 100kΩ, large enough not to
_____________
_____________
load RESET and small enough to pull RESET to ground.
Monitoring Additional Supply Levels
It is possible to use the power-fail comparator to monitor a second supply as shown in figure 8.
The two sensing resistors, R1 and R2, are selected such that the voltage on PFI drops below 1.25V
_________
________
at the minimum acceptable input supply. The PFO output can be connected to the M R input
so that a reset is generated when the supply drops out of tolerance. In this case, if either supply
drops out of tolerance, a reset is generated.
Monitoring a Negative Voltage
The power-fail comparator can also monitor a negative supply rail (Figure 9). When the negative
________
rail is good (a negative voltage of large magnitude), PFO is low, and when the negative rail is
________
degraded (a negative voltage of lesser magnitude), PFO is high. By adding the resistors and
________
________
transistor as shown, a high PFO triggers reset. As long as PFO remains high,
_____________
theUM706xS/UM708xS will keep reset asserted (RESET = low, RESET = high). Note that this
circuit’s accuracy depends on the PFI threshold tolerance, the VCC line, and the resistors.
Microprocessor with Bidirectional Reset
To prevent contention for microprocessors with a bidirectional reset line, a current limiting
_____________
resistor is to be inserted between the RESET output pin and the microprocessor reset pin. This
limits the current to a safe level if there are conflicting output reset levels. A suitable resistor
value is 4.7kΩ. I f the reset output is required for other uses, it should be buffered as shown in
figure 10.
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VX
+5V
VCC
To μP
VCC
RESET
R1
R2
RESET
MR
R1
PFI
PFO
GND
GND
Figure 7. Reset Valid to Ground Circuit
Figure 8. Monitoring an Additional Supply VX
+5V
100kΩ
VCC
MR
R1
100kΩ
BUFFERED RESET TO OTHER SYSTEM COMPONENTS
PFI
PFO
2N3904
RESET
GND
To μP
R2
VCC
VCC
µP
V-
+5V
4.7kΩ
RESET
RESET
MR
0V
+5V
PFO
0V
GND
GND
V-
VTRIP
0V
5-1.25
R1
1.25-VTRIP
R2
,VTRIP＜0
=
Figure 9. Monitoring a Negative Voltage
Figure 10. Bidirectional Reset I/O
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Package Information
UM706xS SOP8
Outline Drawing
c
D
DIMENSIONS
MILLIMETERS
INCHES
Min
Symbol
Min
1.350
0.100
1.350
0.33
Max
1.750
0.250
1.550
0.51
Max
0.069
0.010
0.061
0.020
0.010
0.200
0.157
0.244
A
A1
A2
b
c
D
E
0.053
0.004
0.053
0.013
0.006
0.185
0.150
0.228
1
2
θ
e
0.170
4.700
3.800
5.800
0.250
5.100
4.000
6.200
Top View
End View
E1
e
1.270 (BSC)
0.050 (BSC)
b
L
θ
0.400
0°
1.270
8°
0.016
0°
0.050
8°
Side View
Land Pattern
NOTES:
1. Compound dimension: 4.90×3.90；
2. Unit: mm;
3. General tolerance ±0.05mm unless otherwise
specified;
4. The layout is just for reference.
1.27
0.50
Tape and Reel Orientation
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UM708xS SOP8
Outline Drawing
c
D
DIMENSIONS
MILLIMETERS
INCHES
Min
Symbol
Min
1.350
0.100
1.350
0.33
Max
1.750
0.250
1.550
0.51
Max
0.069
0.010
0.061
0.020
0.010
0.200
0.157
0.244
A
A1
A2
b
c
D
E
0.053
0.004
0.053
0.013
0.006
0.185
0.150
0.228
1
2
θ
e
0.170
4.700
3.800
5.800
0.250
5.100
4.000
6.200
Top View
End View
E1
e
1.270 (BSC)
0.050 (BSC)
b
L
θ
0.400
0°
1.270
8°
0.016
0°
0.050
8°
Side View
Land Pattern
NOTES:
1. Compound dimension: 4.90×3.90；
2. Unit: mm;
3. General tolerance ±0.05mm unless otherwise
specified;
1.27
0.50
4. The layout is just for reference.
Tape and Reel Orientation
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IMPORTANT NOTICE
The information in this document has been carefully reviewed and is believed to be
accurate. Nonetheless, this document is subject to change without notice. Union assumes
no responsibility for any inaccuracies that may be contained in this document, and makes
no commitment to update or to keep current the contained information, or to notify a
person or organization of any update. Union reserves the right to make changes, at any
time, in order to improve reliability, function or design and to attempt to supply the best
product possible.
Union Semiconductor, Inc
Add: 2F, No. 3, Lane647 Songtao Road, Shanghai 201203
Tel: 021-51093966
Fax: 021-51026018
Website: www.union-ic.com
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