AMS AMS811 Precision monitoring of 3v, 3.3v, and 5v power-supply voltage Datasheet

AMS811/812
General Description
Features
The AMS811 / 812 are low-power microprocessor
(µP) supervisory circuits used to monitor power supplies in µP and digital systems. They provide excellent
circuit reliability and low cost by eliminating external
components and adjustments when used with 5Vpowered or 3V-powered circuits. The AMS811 / 812
also provide a debounced manual reset input.
These devices perform a single function: They assert a
reset signal whenever the V CC supply voltage falls
below a preset threshold, keeping it asserted for at
least 140ms after VCC has risen above the reset threshold. The only difference between the two devices is that
the AMS811 has an active-low RESET output (which is
guaranteed to be in the correct state for VCC down to
1V), while the AMS812 has an active-high RESET output. The reset comparator is designed to ignore fast
transients on VCC. Reset thresholds are available for
operation with a variety of supply voltages.
Low supply current makes the AMS811 / 812 ideal
for use in portable equipment. The devices come in a
4-pin SOT143 package.
♦ Precision Monitoring of 3V, 3.3V, and 5V
Power-Supply Voltages
________________________Applications
Computers
♦ 6µA Supply Current
♦ 140ms Min Power-On Reset Pulse Width;
RESET Output (AMS811), RESET Output (AMS812)
♦ Guaranteed Over Temperature
♦ Guaranteed RESET Valid to VCC = 1V (AMS811)
♦ Power-Supply Transient Immunity
♦ No External Components
♦ 4-Pin SOT143 Package
_______________Ordering Information
PART*
AMS811_EUS-T
AMS812_EUS-T
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
-40°C to +85°C
4 SOT143
4 SOT143
*This part offers a choice of five different reset threshold voltages. Select the letter corresponding to the desired nominal
reset threshold voltage, and insert it into the blank to complete
the part number.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Controllers
RESET THRESHOLD
Intelligent Instruments
SUFFIX
VOLTAGE (V)
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
___________Typical Operating Circuit
L
4.63
M
4.38
T
3.08
S
2.93
R
2.63
___________________Pin Configuration
TOP VIEW
VCC
VCC
VCC
AMS811
AMS812
μP
RESET
(RESET)
MR
GND
4
VCC
3
MR
AMS811
AMS812
RESET
INPUT
(RESET) RESET
GND
1
2
GND
SOT143
PUSHBUTTON
SWITCH
( ) ARE FOR AMS812
( ) ARE FOR AMS812
NOTE: SEE LAST PAGE FOR MARKING INFORMATION.
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AMS811/812
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
VCC ......................................................................-0.3V to 6.0V
All Other Inputs.......................................-0.3V to (VCC + 0.3V)
Input Current, VCC, MR .......................................................20mA
Output Current, RESET or RESET .......................................20mA
Continuous Power Dissipation (TA = +70°C)
SOT143 (derate 4mW/°C above +70°C) .......................320mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Operating Voltage Range
VCC
Supply Current
ICC
CONDITIONS
TA = 0°C to +70°C
1.0
TA = -40°C to +85°C
1.2
AMS81_L/M, VCC = 5.5V, IOUT = 0
AMS81_R/S/T, VCC = 3.6V, IOUT = 0
AMS81_L
AMS81_M
Reset Threshold
VTH
MIN
AMS81_T
AMS81_S
AMS81_R
TA = +25°C
4.54
TA = -40°C to +85°C
4.50
TA = +25°C
4.30
TA = -40°C to +85°C
4.25
TA = +25°C
3.03
TA = -40°C to +85°C
3.00
TA = +25°C
2.88
TA = -40°C to +85°C
2.85
TA = +25°C
2.58
TA = -40°C to +85°C
2.55
Reset Threshold Tempco
Reset Active Timeout Period
tRP
MR Minimum Pulse Width
tMR
5.5
6
15
2.7
10
4.63
4.72
4.38
4.46
3.08
3.14
MR to Reset Propagation Delay
(Note 2)
3.15
2.93
VIH
VIL
VIH
VIL
2.63
2.98
2.68
µs
560
10
ISOURCE = 150µA, 1.8V < VCC < VTH(MIN)
µs
100
ns
0.5
µs
0.8
0.7 x VCC
V
0.25 x VCC
20
30
kΩ
0.8 x VCC
AMS812R/S/T only, SINK
I
= 1.2mA,
VCC = VTH(MAX)
0.3
AMS812L/M only, SINK
I
= 3.2mA,
VCC = VTH(MAX)
0.4
2
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ms
2.3
VCC > VTH(MAX) , AMS81_L/M
10
VOL
ppm/°C
140
MR Pull-Up Resistance
VOH
V
2.70
20
VCC > VTH(MAX) , AMS81_R/S/T
µA
3.00
VOD = 125mV, AMS81_R/S/T
tMD
V
4.50
40
VCC = VTH(MAX)
UNITS
4.75
VOD = 125mV, AMS81_L/M
MR Glitch Immunity (Note 3)
RESET Output Voltage
(AMS812)
MAX
30
VCC to Reset Delay (Note 2)
MR Input Threshold
TYP
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V
AMS811/812
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
VOL
RESET Output Voltage
(AMS811)
CONDITIONS
MIN
MAX
0.3
AMS811L/M only, SINK
I
= 3.2mA,
VCC = VTH(MIN)
0.4
ISINK = 50µA, VCC > 1.0V
VOH
TYP
AMS811R/S/T only, SINK
I
= 1.2mA,
VCC = VTH(MIN)
0.3
AMS811R/S/T only, SOURCE
I
= 500µA,
VCC > VTH(MAX)
0.8 x VCC
AMS811L/M only, SOURCE
I
= 800µA,
VCC > VTH(MAX)
VCC - 1.5
Note 1: Production testing done at TA = +25°C, over temperature limits guaranteed by design using six sigma design limits.
Note 2: RESET output for AMS811, RESET output for AMS812.
Note 3: “Glitches” of 100ns or less typically will not generate a reset pulse.
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UNITS
V
AMS811/812
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
3.0
VCC = 3.3V
2.0
1.5
1.0
VCC = 5.5V
6
4
VCC = 3V
2
0.5
POWER-DOWN RESET DELAY (μs)
VCC = 3.6V
SUPPLY CURRENT (μA)
VCC = 1V
-40
-15
10
35
60
85
-40
POWER-DOWN RESET DELAY vs. TEMPERATURE
(AMS81_L/M)
POWER-UP RESET TIMEOUT
vs. TEMPERATURE
POWER-UP RESET TIMEOUT (ms)
100
VOD = 125mV
VOD = 200mV
-40
-15
10
35
60
40
VOD = 125mV
20
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
RESET THRESHOLD DEVIATION
vs. TEMPERATURE
1.0005
AMS81_R/S/T
VOD = 20mV
0
-15
230
VOD = VTH - VCC
50
60
VOD = 200mV
10
35
TEMPERATURE (°C)
150
VOD = 20mV
80
0
TEMPERATURE (°C)
200
VOD = VTH - VCC
VCC = 1V
0
0
NORMALIZED THRESHOLD (V)
SUPPLY CURRENT (μA)
100
8
2.5
POWER-DOWN RESET DELAY (μs)
POWER-DOWN RESET DELAY vs. TEMPERATURE
(AMS81_R/S/T)
SUPPLY CURRENT vs. TEMPERATURE
(AMS81_L/M)
SUPPLY CURRENT vs. TEMPERATURE
(AMS81_R/S/T)
220
210
200
AMS81_L/M
190
85
1.0000
0.9995
0.9990
0.9985
0.9980
-40
-15
TEMPERATURE (°C)
10
35
60
85
TEMPERATURE (°C)
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-40
-15
10
35
TEMPERATURE (°C)
60
85
AMS811/812
Pin Description
PIN
NAME
FUNCTION
AMS811
AMS812
1
1
GND
2
—
RESET
Active-Low Reset Output. RESET remains low while VCC is below the reset threshold or while
MR is held low. RESET remains low for the Reset Active Timeout Period (tRP) after the reset
conditions are terminated.
—
2
RESET
Active-High Reset Output. RESET remains high while VCC is below the reset threshold or while
MR is held low. RESET remains high for Reset Active Timeout Period (tRP) after the reset conditions are terminated.
3
3
MR
Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR is
low and for 180ms after MR returns high. This active-low input has an internal 20kΩ pull-up
resistor. It can be driven from a TTL or CMOS-logic line, or shorted to ground with a switch.
Leave open if unused.
4
4
VCC
+5V, +3.3V, or +3V Supply Voltage
Ground
_______________ Detailed Description
Reset Output
A microprocessor’s (µP’s) reset input starts the µP in a
known state. These µP supervisory circuits assert reset
to prevent code execution errors during power-up,
power-down, or brownout conditions.
RESET is guaranteed to be a logic low for VCC > 1V.
Once V CC exceeds the reset threshold, an internal
timer keeps RESET low for the reset timeout period;
after this interval, RESET goes high.
If a brownout condition occurs (VCC dips below the
reset threshold), RESET goes low. Any time VCC goes
below the reset threshold, the internal timer resets to
zero, and RESET goes low. The internal timer starts
after VCC returns above the reset threshold, and RESET
remains low for the reset timeout period.
The manual reset input (MR) can also initiate a reset.
See the Manual Reset Input section.
The AMS812 has an active-high RESET output that is
the inverse of the AMS811’s RESET output.
Manual Reset Input
Many µP-based products require manual reset capability, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on MR
asserts reset. Reset remains asserted while MR is low,
and for the Reset Active Timeout Period (tRP) after MR
returns high. This input has an internal 20kΩ pull-up
resistor, so it can be left open if it is not used. MR can
be driven with TTL or CMOS-logic levels, or with opendrain/collector outputs. Connect a normally open
momentary switch from MR to GND to create a manualreset function; external debounce circuitry is not
required. If MR is driven from long cables or if the
device is used in a noisy environment, connecting a
0.1µF capacitor from MR to ground provides additional
noise immunity.
Reset Threshold Accuracy
The AMS811/AMS812 are ideal for systems using a 5V
±5% or 3V ±5% power supply with ICs specified for 5V
±10% or 3V ±10%, respectively. They are designed to
meet worst-case specifications over temperature. The
reset is guaranteed to assert after the power supply
falls out of regulation, but before power drops below
the minimum specified operating voltage range for the
system ICs. The thresholds are pre-trimmed and exhibit
tight distribution, reducing the range over which an
undesirable reset may occur.
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AMS811/812
MAXIMUM TRANSIENT DURATION (ms)
8
TA = +25°C
7
6
VCC
AMS81 _L/M
5
AMS811
4
AMS81 _R/S/T
3
RESET
R1
2
GND
1
0
1
10
100
1000
RESET COMPARATOR OVERDRIVE , VTH - VCC (mV)
Figure 2. RESET Valid to VCC = Ground Circuit
Figure 1. Maximum Transient Duration without Causing a
Reset Pulse vs. Comparator Overdrive
__________ Applications Information
Negative-Going VCC Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the AMS811/
AMS812 are relatively immune to short duration negative-going VCC transients (glitches).
Figure 1 shows typical transient durations vs. reset
comparator overdrive, for which the AMS811/AMS812
do not generate a reset pulse. This graph was generated using a negative-going pulse applied to VCC, starting above the actual reset threshold and ending below
it by the magnitude indicated (reset comparator overdrive). The graph indicates the typical maximum pulse
width a negative-going VCC transient may have without
causing a reset pulse to be issued. As the magnitude
of the transient increases (goes farther below the reset
threshold), the maximum allowable pulse width
decreases. Typically, a VCC transient that goes 125mV
below the reset threshold and lasts 40µs or less
(AMS81_L/M) or 20µs or less (AMS81_T/S/R) will not
cause a reset pulse to be issued. A 0.1µF capacitor
mounted as close as possible to VCC provides additional transient immunity.
Ensuring a Valid RESET Output
Down to VCC = 0V
When VCC falls below 1V, the AMS811 RESET output
no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS-logic inputs connected to the RESET output can drift to undetermined
voltages. This presents no problem in most applications, since most µP and other circuitry is inoperative
with VCC below 1V. However, in applications where the
RESET output must be valid down to 0V, adding a pulldown resistor to the RESET pin will cause any stray
leakage currents to flow to ground, holding RESET low
(Figure 2). R1’s value is not critical; 100kΩ is large
enough not to load RESET and small enough to pull
RESET to ground.
A 100kΩ pull-up resistor to VCC is also recommended
for the AMS812 if RESET is required to remain valid for
VCC < 1V.
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AMS811/812
Interfacing to µPs with
Bidirectional Reset Pins
µPs with bidirectional reset pins (such as the Motorola
68HC11 series) can contend with the AMS811/AMS812
reset outputs. If, for example, the AMS811 RESET output is asserted high and the µP wants to pull it low,
indeterminate logic levels may result. To correct such
cases, connect a 4.7kΩ resistor between the AMS811
RESET (or AMS812 RESET) output and the µP reset I/O
(Figure 3). Buffer the reset output to other system components.
BUFFER
BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
VCC
VCC
AMS811
μP
4.7k
RESET
GND
RESET
GND
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
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AMS811/812
Package Information
4.0 ±0.1
2.0 ±0.05
ø1.5 ±0.1
1.75 ±0.1
8.0 ±0.2
4.0 ±0.1
ø1.1 ±0.1
3.5 ±0.05
NOTE: DIMENSIONS ARE IN MM.
AND FOLLOW EIA481-1 STANDARD.
MARKING
INFORMATION †
LOT SPECIFIC
CODE
XX XX
AMAA or KABB = AMS811L
ANAA or KABC = AMS811M
APAA or KABD = AMS811T
AQAA or KABE = AMS811S
ARAA or KABF = AMS811R
ASAA or KABG = AMS812L
ATAA or KABH = AMS812M
AVAA or KABI = AMS812T
AWAA or KABJ = AMS812S
AXAA or KABK = AMS812R
SOT-23 5L .EPS
† ICs MAY ALSO BE MARKED WITH FULL PART NAME: 811L, 811M_…
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