LM3724EM5X-3.08/NOPB [NSC]
1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, SOT-23, 5 PIN;
| 型号： | LM3724EM5X-3.08/NOPB |
| 厂家： | 
National Semiconductor |
| 描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, SOT-23, 5 PIN 光电二极管 |
| 文件： | 总13页 (文件大小：324K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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July 2007
LM3722/LM3723/LM3724
5-Pin Microprocessor Reset Circuits
General Description
Features
The LM3722/LM3723/LM3724 microprocessor supervisory
circuits monitor the power supplies in microprocessor and
digital systems. They provide a reset to the microprocessor
during power-up, power-down, brown-out conditions, and
manual reset.
Precise monitoring of 2.5V, 3.3V, and 5V supply voltages
■
■
Fully specified over temperature
Industrial: −40°C to +85°C
Extended: −40°C to +125°C
100 ms minimum Power-On Reset pulse width, 190 ms
typical:
■
The LM3722/LM3723/LM3724 asserts a reset signal when-
ever the supply decreases below the factory-programmed
reset threshold. Reset will be asserted for at least 100ms even
after VCC rises above the reset threshold.
Active-Low RESET Output (LM3722)
Active-High RESET Output (LM3723)
Active-Low RESET Open Drain Output (LM3724)
The LM3722 has an active-low RESET push-pull output. The
LM3723 has an active-high RESET push-pull output. The
LM3724 has an active-low open-drain RESET output.
Guaranteed RESET Output valid for VCC ≥ 1V
Low Supply Current, 6µA typical
■
■
■
■
Power supply transient immunity
Three standard reset voltage options are available, suitable
for monitoring 5V, 3.3V, and 2.5V supply voltages. Additional
reset voltages are also available; contact National Semicon-
ductor for details.
Compatible with MAX811/812 applications
Applications
With a low supply current of only 6µA, the LM3722/LM3723/
LM3724 are ideal for use in portable equipment. The LM3722/
LM3723/LM3724 are available in the 5-pin SOT23 package.
Microprocessor Systems
■
■
■
■
Computers
Controllers
Intelligent Instruments
Portable/Battery-Powered Equipment
■
Typical Application Circuit
20014401
20014437
Connection Diagram
SOT23-5
20014402
*( ) are for LM3723
© 2007 National Semiconductor Corporation
200144
www.national.com
Ordering Information
Industrial Temperature Range (−40°C to +85°C):
Reset Threshold LM3722 Supplied as 1000 LM3722 Supplied as 3000
Package
Top Mark
Package Type NSC Package
(V)
units, tape & reel
LM3722IM5-4.63
LM3722IM5-3.08
LM3722IM5-2.32
units, tape & reel
LM3722IM5X-4.63
LM3722IM5X-3.08
LM3722IM5X-2.32
4.63
3.08
2.32
R43B
R41B
R34B
SOT23-5
MF05A
Reset Threshold LM3723 Supplied as 1000 LM3723 Supplied as 3000
Package
Top Mark
Package Type NSC Package
(V)
units, tape & reel
LM3723IM5-4.63
LM3723IM5-3.08
LM3723IM5-2.32
units, tape & reel
LM3723IM5X-4.63
LM3723IM5X-3.08
LM3723IM5X-2.32
4.63
3.08
2.32
R13B
R11B
R46B
SOT23-5
MF05A
Reset Threshold LM3724 Supplied as 1000 LM3724 Supplied as 3000
Package
Top Mark
Package Type NSC Package
(V)
units, tape & reel
LM3724IM5-4.63
LM3724IM5-3.08
LM3724IM5-2.32
units, tape & reel
LM3724IM5X-4.63
LM3724IM5X-3.08
LM3724IM5X-2.32
4.63
3.08
2.32
R55B
R53B
R50B
SOT23-5
MF05A
Extended Temperature Range (−40°C to +125°C):
Reset Threshold LM3722 Supplied as 1000 LM3722 Supplied as 3000
Package
Package Type NSC Package
(V)
units, tape & reel
LM3722EM5-4.63
LM3722EM5-3.08
LM3722EM5-2.32
units, tape & reel
LM3722EM5X-4.63
LM3722EM5X-3.08
LM3722EM5X-2.32
Top Mark
4.63
3.08
2.32
R56B
R57B
SOT23-5
MF05A
R58B
Reset Threshold LM3723 Supplied as 1000 LM3723 Supplied as 3000
Package
Top Mark
Package Type NSC Package
(V)
units, tape & reel
LM3723EM5-4.63
LM3723EM5-3.08
LM3723EM5-2.32
units, tape & reel
LM3723EM5X-4.63
LM3723EM5X-3.08
LM3723EM5X-2.32
4.63
3.08
2.32
R59B
R60
SOT23-5
MF05A
R61B
Reset Threshold LM3724 Supplied as 1000 LM3724 Supplied as 3000
Package
Top Mark
Package Type NSC Package
(V)
units, tape & reel
LM3724EM5-4.63
LM3724EM5-3.08
LM3724EM5-2.32
units, tape & reel
LM3724EM5X-4.63
LM3724EM5X-3.08
LM3724EM5X-2.32
4.63
3.08
2.32
R62B
R63B
R64B
SOT23-5
MF05A
Custom voltages and improved accuracies are available, subject to minimum orders. Contact your local National Semiconductor Sales Office for information.
www.national.com
2
Pin Descriptions
PIN
1
NAME
GND
FUNCTION
Ground reference
2
GND
Ground reference, device substrate, connect to ground.
Active-low output. RESET remains low while VCC is below the reset threshold voltage,
and for 190 ms after VCC rises above the reset threshold voltage.
RESET
LM3722/LM3724
3
Active-high output. RESET remains high while VCC is below the reset threshold, and for
190 ms after VCC rises above the reset threshold.
RESET
LM3723
Active-low input. Reset is asserted whenever this pin is pulled low and remains asserted
for 190 ms after the MR pin goes high. May be left open.
4
5
MR
VCC
Supply Voltage (+5V, +3.3V, or +2.5V, nominal)
Block Diagram
LM3722/LM3723/LM3724 Block Diagram
20014435
3
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Continuous Power Dissipation (TA = +70°C)
SOT-23 (Note 3)
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
320mW
Operating Temperature Range
Industrial:
−40°C to +85°C
Extended:
−40°C to +125°C
125°C
−65°C to +160°C
+300°C
VCC, MR
−0.3V to 6.0V
−0.3V to (VCC+ 0.3V)
Maximum Junction Temperature
Storage Temperature Range
Lead Temperature (soldering, 10sec)
RESET, RESET
Input Current, VCC Pin
Output Current, RESET, RESET Pin
ESD Rating (Note 2)
20mA
20mA
2kV
Electrical Characteristics
Typical values are at TA = +25°C. Limits with standard typeface are for TA = +25°C, and limits in boldface type apply for the operating
temperature range (−40°C to +85°C) for LM372_IM5X, and (−40°C to +125°C) for LM372_EM5X, unless otherwise noted. (Note
4)
Symbol
Parameter
VCC Range
Conditions
Min
1.0
Typ
Max
5.5
15
Units
V
VCC
LM372 _ -4.63
LM372 _ -3.08
LM372 _ -2.32
VCC = 5.5V
VCC = 3.6V
VCC = 2.5V
8
7
µA
Supply Current
(ILOAD = 0A)
ICC
10
6
10
4.54
4.50
4.63
4.72
4.75
LM372 _ -4.63
LM372 _ -3.08
LM372 _ -2.32
3.03
3.00
3.08
2.32
3.14
3.15
VTH
Reset Threshold
V
2.27
2.25
2.37
2.40
VTH
Tempco
tRD
Reset Threshold Temperature
Coefficient
30
ppm/°C
VCC to Reset Delay (Note 5)
Reset Active Timeout Period
MR Minimum Pulse Width
VCC = VTH to (VTH − 100mV)
20
µs
ms
µs
tRP
tMR
100
10
190
560
MR to Reset Propagation
Delay
tMD
2
µs
ns
MR Glitch Immunity (Note 6)
100
VIH
VIL
VIH
VIL
2.3
VCC > VTH(MAX), LM372_ -4.63
0.8
0.25 VCC
0.3
MR Input Threshold
V
0.7 VCC
VCC > VTH(MAX), LM372_ -3.08, LM372_ -2.32
MR Pull-Up Resistance
22
kΩ
VCC = VTH min, ISINK = 1.2mA,
(LM3722-2.32/3.08)
RESET Output Voltage Low
(LM3722)
VOL
V
VCC = VTH min, ISINK = 3.2mA, (LM3722-4.63)
0.4
0.3
VCC > 1V, ISINK = 50µA
VCC > VTH max, ISOURCE = 500µA,
(LM3722-2.32/3.08)
0.8VCC
RESET Output Voltage High
(LM3722)
VOH
V
VCC > VTH max, ISOURCE = 800µA,
(LM3722-4.63)
VCC−1.5
VCC = VTH max, ISINK = 1.2mA
(LM3723 -2.32/3.08)
0.3
0.4
RESET Output Voltage Low
(LM3723)
VOL
V
V
VCC = VTH max, ISINK = 3.2mA
(LM3723 -4.63)
VOH
RESET Output Voltage High
(LM3723)
0.8VCC
1.8V < VCC < VTH min, ISOURCE = 150µA
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4
Symbol
Parameter
Conditions
VCC = VTH min, ISINK = 1.2 mA
(LM3724 -2.32/3.08)
Min
Typ
Max
0.3
Units
VOL
RESET Output Voltage Low
(LM3724)
V
VCC = VTH min, ISINK = 3.2 mA
(LM3724 -4.63)
0.4
VCC > 1V, ISINK = 50µA
0.3
0.5
IIN
RESET Output Leakage
Current (LM3724)
µA
VCC > VTH, RESET = 5.5V
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which the device operates
correctly. Operating ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical
Characteristics.
Note 2: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin.
Note 3: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the SOT23-5 package must be derated at 4.5mW/
°C at ambient temperatures above 70°C. The device has internal thermal protection.
Note 4: Production testing done at TA = +25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control
(SQC) methods.
Note 5: RESET Output for LM3722 and LM3724, RESET output for LM3723.
Note 6: Glitches of 100 ns or less typically will not generate a reset pulse.
Typical Performance Characteristics
Supply Current vs VCC
Supply Current vs Temperature
20014407
20014403
Reset Timeout vs VCC
Reset Timeout vs Temperature
20014408
20014404
5
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Normalized VTH vs Temperature
LM3724 VOL vs Current
20014416
20014405
LM3724 Low VCC Characteristics
20014406
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6
Timing Diagram
20014412
itoring 5.0V, 3.3V, and 2.5V supplies respectively. Other reset
thresholds in the 2.20V to 5.0V range, in 10 mV steps, are
available; contact National Semiconductor for details.
Circuit Information
RESET OUTPUT
The reset input of a µP initializes the device into a known
state. The LM3722/LM3723/LM3724 microprocessor voltage
monitoring circuits assert a forced reset output to prevent
code execution errors during power-up, power-down, and
brownout conditions.
MANUAL RESET INPUT (MR)
Many µP-based products require a manual reset capability,
allowing the operator to initiate a reset. The MR input is fully
debounced and provides an internal 22 kΩ pull-up. When the
MR input is pulled below VIL (0.25VCC) for more than 100 ns,
reset is asserted after a typical delay of 2 µs. Reset remains
active as long as MR is held low, and releases after MR rises
above VIH and the reset timeout period expires. Use MR with
digital logic to assert reset or to daisy chain supervisory cir-
cuits.
RESET is guaranteed valid for VCC ≥ 1V. Once VCC exceeds
the reset threshold, an internal timer maintains the output for
the reset timeout period. After this interval, reset goes high
and the microprocessor initializes itself into a known state.
The LM3722 and LM3724 offer an active-low RESET; the
LM3723 offers an active-high RESET.
As VCC drops below the reset threshold (such as during a
brownout), the reset activates (see the Negative-Going VCC
Transients section). When VCC again rises above the reset
threshold, the internal timer starts. Reset holds until VCC ex-
ceeds the reset threshold for longer than the reset timeout
period. After this time, reset releases.
Applications Information
BENEFITS OF PRECISION RESET THRESHOLDS
A microprocessor supply supervisor must provide a reset out-
put within a predictable range of the supply voltage. A com-
mon threshold range is between 5% and 10% below the
nominal supply voltage. The 4.63V, 3.08V and 2.32V options
of the LM3722/LM3723/LM3724 use highly accurate circuitry
to ensure that the reset threshold occurs only within this range
(for 5.0V, 3.3V and 2.5V supplies). Table 1 shows how the
standard reset thresholds apply to 5.0V, 3.3V, and 2.5V nom-
inal supply voltages.
Additionally, the Manual Reset input (MR) will initiate a forced
reset. See the Manual Reset Input section.
The LM3722/LM3723/LM3724 reset outputs ignore short du-
ration glitches on VCC and MR. See the Applications Informa-
tion section for details.
RESET THRESHOLD
The LM3722/LM3723/LM3724 are available with reset volt-
ages of 4.63V, 3.08V, and 2.32V which are suitable for mon-
7
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TABLE 1. Monitored Tolerance Table
nected devices does not create an excessive voltage drop
when the output is not activated. A resistor value of 100 kΩ
will generally suffice.
Supply Voltage
3.3V
Reset
Threshold
2.5V
5.0V
NEGATIVE-GOING VCC TRANSIENTS
4.63 ± %
3.08 ± %
2.32 ± %
90.8-94.4
%
The LM3722/LM3723/LM3724 are relatively immune to short
negative-going transients or glitches on VCC. Figure 2 shows
the maximum pulse width a negative-going VCC transient can
have without causing a reset pulse. In general, as the mag-
nitude of the transient increases, going further below the
threshold, the maximum allowable pulse width decreases.
Typically, a VCC transient that goes 125 mV below the reset
threshold and lasts 40 µs or less will not cause a reset pulse.
A 0.1 µF bypass capacitor mounted as close as possible to
the VCC pin will provide additional transient rejection.
91.8-95.2
%
90.8-94.8
%
ENSURING A VALID RESET OUTPUT DOWN TO VCC = 0V
When VCC falls below 1V, the LM3722 RESET output is un-
able to sink the rated current. A high-impedance CMOS logic
input connected to RESET can therefore drift to undetermined
voltages. To prevent this situation, a 100kΩ resistor should
be connected from the RESET output to ground, as shown in
Figure 1.
A 100kΩ pull-up resistor to VCC is also recommended for the
LM3723, if RESET is required to remain valid for VCC < 1V.
20014414
20014410
FIGURE 2. Maximum Transient Duration without Causing
a Reset Pulse vs. Reset Comparator Overdrive
FIGURE 1. Circuit for RESET Valid from VCC = 0V
INTERFACING TO µPS WITH BIDIRECTIONAL RESET
PINS
OPEN DRAIN OUTPUT (LM3724)
An open drain output allows easy paralleling of multiple mi-
croprocessor reset circuits without requiring additional logic
gates. Open drain outputs also allow interfacing devices of
differing logic levels or families, since the output pull-up re-
sistor may be connected to any supply voltage up to 5.5V,
Microprocessors with bidirectional reset pins, such as the
Motorola 68HC11 series, can be connected to the LM3722
RESET output. To ensure a correct output on the LM3722
even when the microprocessor reset pin is in the opposite
state, connect a 4.7kΩ resistor between the LM3722 RE-
SET output and the µP reset pin, as shown in Figure 3. Buffer
the LM3722 RESET output to other system components.
regardless of LM3724 VCC
.
The pull up resistor is calculated so that maximum current flow
into RESET is less than 10 mA when activated. The resistor
must be small enough so that the leakage current of all con-
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8
Typical Application Circuits
20014411
FIGURE 3. Interfacing to Microprocessors with Bidirectional Reset I/O
20014422
FIGURE 4. Regulator/Switch with Long-Term Overvoltage Lockout Prevents Overdissipation in Linear Regulator
9
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20014431
FIGURE 5. LM3722 Switch Debouncer
20014424
FIGURE 6. LM3723 Power-On Delay
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10
Physical Dimensions inches (millimeters) unless otherwise noted
5-Lead SOT23-5
For Ordering, refer to Ordering Information table
NS Package Number MF05A
11
www.national.com
Notes
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Copyright© 2007 National Semiconductor Corporation
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相关型号：
LM3724IM5-2.32/NOPB
IC 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, SOT-23, 5 PIN, Power Management Circuit
NSC
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