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LM3709XQBP-308中文资料

LM3708/LM3709

Microprocessor Supervisory Circuits with Low Line Output,Manual Reset and Watchdog Timer

General Description

The LM3708/LM3709series of microprocessor supervisory circuits provide the maximum flexibility for monitoring power supplies and battery controlled functions in systems without backup batteries.The LM3708/LM3709series are available in a 9-bump micro SMD package.Built-in features include the following:

Reset:Reset is asserted during power-up,power-down,and brownout conditions.RESET is guaranteed down to V CC of 1.0V.

Manual Reset Input:An input that asserts reset when pulled low.

Low Line Output:This early power failure warning indicator goes low when the supply voltage drops to a value which is 2%higher than the reset threshold voltage.

Watchdog Timer:The WDI (Watchdog Input)monitors one of the μP’s output lines for activity.If no output transition occurs during the watchdog timeout period,reset is activated.

Features

n Standard Reset Threshold voltage:3.08V

n Custom Reset Threshold voltages:For other voltages between 2.2V and 5.0V in 10mV increments,contact National Semiconductor Corp.n No external components required n Manual-Reset input

n RESET (LM3708)or RESET (LM3709)outputs n Precision supply voltage monitor

n Factory programmable Reset and Watchdog Timeout Delays

n Available in micro SMD package for minimum footprint n ±0.5%Reset threshold accuracy at room temperature n ±2%Reset threshold accuracy over temperature extremes

n Reset assertion down to 1V V CC (RESET option only)n 28μA V CC supply current

Applications

n Embedded Controllers and Processors n Intelligent Instruments n Automotive Systems

Critical μP Power Monitoring

Typical Application

20011703

June 2002

LM3708/LM3709Microprocessor Supervisory Circuits with Low Line Output,Manual Reset and Watchdog Timer

?2002National Semiconductor Corporation https://www.wendangku.net/doc/6214928373.html,

Connection Diagram

Top View

(looking from the coating side)micro SMD 9Bump Package

BPA09

20011701

Pin Descriptions

Bump No.

Name Function

A1MR Manual-Reset input.When MR is less than V MRT (Manual Reset Threshold)RESET/RESET is engaged.B1V CC Power Supply input.

RESET

Reset Logic Output.Pulses low for t RP (Reset Timeout Period)when triggered,and stays low whenever V CC is below the reset threshold or when MR is below V MRT .It remains low for t RP after either V CC rises above the reset threshold,or after MR input rises above V MRT (LM3708only).

RESET

Reset Logic Output.RESET is the inverse of RESET (LM3709only).

LLO

Low-Line Logic Output.Early Power-Fail warning output.Low when V CC falls below V LLOT (Low-Line Output Threshold).This output can be used to generate an NMI (Non-Maskable Interrupt)to provide an early warning of imminent power-failure.B3GND Ground reference for all signals.

A3WDI Watchdog Input Transition Monitor:If no transition activity occurs for a period exceeding t WD (Watchdog Timeout Period),reset is engaged.A2,C2NC No Connect.

No Connect.Test input used at factory only.Leave floating.

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Block Diagram

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Ordering Information

20011704

*For other voltages between 2.2V and 5.0V,please contact National Semiconductor sales office.

LM3708/LM3709

Part Number Output Reset Timeout

Period

Watchdog Timeout Period

Package Marking LM3708XQBP-308totem-pole 200ms 1600ms %%I8LM3708XQBPX-308totem-pole 200ms 1600ms %%I8LM3709XQBP-308totem-pole 200ms 1600ms %%I9LM3709XQBPX-308

totem-pole

200ms

1600ms

%%I9

%%is the datecode and will vary with time.

Table Of Functions

Part Number Active Low Reset Active High Reset

Output

(X =totem-pole)(Y =open-drain)

Reset Timeout Period Watchdog Timeout Period Manual Reset Low Line Output LM3708x

X,Y *Customized Customized x x LM3709

x X

Customized

*=available upon request.Contact National

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Absolute Maximum Ratings

(Note 1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.Supply Voltage (V CC )?0.3V to 6.0V

All Other Inputs ?0.3V to V CC +0.3V

ESD Ratings (Note 2)Human Body Model Machine Model

1.5kV 150V

Power Dissipation (Note 3)

Operating Ratings (Note 1)

Temperature Range

?40?C ≤T J ≤85?C

LM3708/LM3709Series Electrical Characteristics

Limits in the standard typeface are for T J =25?C and limits in boldface type apply over full operating range.Unless otherwise specified:V CC =+2.2V to 5.5V.Symbol Parameter Conditions

Min Typ

Max Units

POWER SUPPLY

V CC Operating Voltage Range:V CC LM3708 1.0 5.5V LM3709

1.2

5.5I CC

V CC Supply Current

All inputs =V CC ;all outputs floating

2850

μA

RESET THRESHOLD V RST

Reset Threshold

V CC falling

?0.5?2V RST

+0.5+2%

V CC falling:T A =0?C to 70?C

?1.5

+1.5

V RSTH Reset Threshold Hysteresis 0.0032?V RST

mV t RP

Reset Timeout Period

Reset Timeout Period =E,J,N,S Reset Timeout Period =F,K,P,T Reset Timeout Period =G,L,Q,U Reset

Timeout

Period

H,M,R,V

1201401120 1.42820016002402802240

t RD

V CC to Reset Delay V CC falling at 1mV/μs

μs

RESET (LM3709)V OL

RESET

V CC >2.25V,I SINK =900μA 0.3V

V CC >2.7V,I SINK =1.2mA 0.3V CC >4.5V,I SINK =3.2mA

0.4

V OH

RESET

V CC >1.2V,I SOURCE =50μA 0.8V CC V

V CC >1.8V,I SOURCE =150μA 0.8V CC V CC >2.25V,I SOURCE =300μA 0.8V CC V CC >2.7V,I SOURCE =500μA 0.8V CC V CC >4.5V,I SOURCE =800μA

V CC ?1.5V

I LKG

Output Leakage Current V RESET =5.5V

1.0

μA RESET (LM3708)V OL

RESET

V CC >1.0V,I SINK =50μA 0.3V

V CC >1.2V,I SINK =100μA 0.3V CC >2.25V,I SINK =900μA 0.3V CC >2.7V,I SINK =1.2mA 0.3V CC >4.5V,I SINK =3.2mA

0.4

V OH

RESET

V CC >2.25V,I SOURCE =300μA 0.8V CC V CC >2.7V,I SOURCE =500μA 0.8V CC V CC >4.5V,I SOURCE =800μA

V CC ?1.5V

LM3708/LM3709

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LM3708/LM3709Series Electrical Characteristics

(Continued)

Limits in the standard typeface are for T J =25?C and limits in boldface type apply over full operating range.Unless otherwise specified:V CC =+2.2V to 5.5V.

Symbol Parameter

Conditions

Min Typ

Max Units WDI WDI Watchdog Input Current ?1

μA

WDI T Watchdog Input Threshold 0.2?V CC

1.2250.8?V CC V

t WD

Watchdog

Timeout Period

Watchdog Timeout Period =E,F,G,H Watchdog Timeout Period =J,K,L,M Watchdog Timeout Period =N,P,Q,R Watchdog Timeout

Period

S,T,U,V

4.371112017900

6.2102160025600

9.3153240038400ms

MR V MRT MR Input Threshold MR,Low 0.8

V MR,High

2.0

V MRTH MR Threshold Hysteresis MR falling:V CC =V RST

MAX

to 5.5V

0.0032?V RST

mV R MR MR Pull-up Resistance 35

5675

k ?t MD MR to Reset Delay

μS t MR MR Pulse Width

25μS

LLO V OL

LLO Output Voltage

V CC >2.25V,I SINK =900μA 0.3V

V CC >2.7V,I SINK =1.2mA 0.3V CC >4.5V,I SINK =3.2mA

0.4

V OH

V CC >2.25V,I SOURCE =300μA 0.8V CC V CC >2.7V,I SOURCE =500μA 0.8V CC V CC >4.5V,I SOURCE =800μA

V CC ?1.5V

LLO OUTPUT V LLOT

LLO Output Threshold

(V LLO ?V RST ,V CC falling) 1.01?V RST

1.02?V RST

1.03?V RST

V LLOTH Low-Line Comparator Hysteresis 0.0032?V RST

t CD

Low-Line

Comparator Delay

V CC falling at 1mV/μs

20μs

Note 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.Operating Ratings indicate conditions for which the device is intended to be functional,but do not guarantee specific performance limits.For guaranteed specifications and test conditions,see the Electrical Characteristics.The guaranteed specifications apply only for the test conditions listed.Some performance characteristics may degrade when the device is not operated under the listed conditions.

Note 2:The Human Body model is a 100pF capacitor discharged through a 1.5k ?resistor into each pin.The machine model is a 200pF capacitor discharged directly into each pin.

Note 3:The maximum allowable power dissipation is a function of the maximum junction temperature,T J (MAX),the junction-to-ambient thermal resistance,θJ-A ,and the ambient temperature,T A .The maximum allowable power dissipation at any ambient temperture is calculated using:

Where the value of θJ-A for the micro SMD package is 220?C/W.

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Typical Performance Characteristics

Supply Current vs Supply Voltage

3.3V Supply Current vs Temperature

20011715

20011711

Normalized Reset Threshold Voltage vs Temperature

Reset Timeout Period vs V CC

20011712

20011732

Reset Timeout Period vs Temperature

Max.Transient Duration vs Reset Comparator Overdrive

(V CC =3.3V)

20011710

20011716

LM3708/LM3709

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Typical Performance Characteristics

(Continued)

Watchdog Timeout Period vs Temperature

(t WD programmed as 6.2ms)

Low-Line Comparator Propagation Delay vs Temperature

20011713

20011714

Circuit Information

Reset Output

The Reset input of a μP initializes the device into a known state.The LM3708/LM3709microprocessor supervisory cir-cuits assert a forced reset output to prevent code execution errors during power-up,power-down,and brownout condi-tions.

RESET is guaranteed valid for V CC >1V.Once V CC ex-ceeds the reset threshold,an internal timer maintains the output for the reset timeout period.After this interval,reset goes high.The LM3708offers an active-low RESET;The LM3709offers an active-high RESET.

Any time V CC drops below the reset threshold (such as during a brownout),the reset activates.When V CC again rises above the reset threshold,the internal timer starts.Reset holds until V CC exceeds the reset threshold for longer than the reset timeout period.After this time,reset releases.The Manual Reset input (MR)will initiate a forced reset also.See the Manual Reset Input section.

Reset Threshold

The LM3708/LM3709family is available with a reset voltage of 3.08V.Other reset thresholds in the 2.20V to 5.0V range,in steps of 10mV,are available;contact National Semicon-ductor for details.

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 56k ?pull-up.When the MR input is pulled below V MRT (1.225V)for more than 25μs,reset is asserted after a typical delay of 12μs.Reset remains active as long as MR is held low,and releases after the reset timeout period expires after MR rises above V MRT .Use MR with digital logic to assert or to daisy chain supervisory circuits.It may be used as another low-line comparator by adding a buffer.

Low-Line Output (LLO)

The low-line output comparator is typically used to provide a non-maskable interrupt to a μP when V CC begins falling.LLO monitors V CC and goes low when V CC falls below V LLOT (typically 1.02?V RST )with hysteresis of 0.0032?V RST .Watchdog Timer Input (WDI)

The watchdog timer input monitors one of the microproces-sor’s output lines for activity.Each time a transition occurs on this monitored line,the watchdog counter is reset.However,if no transition occurs and the timeout period is reached,the LM3708/LM3709assumes that the microprocessor has locked up and the reset output is activated.WDI is a high impedance input.

Special Precautions for the micro SMD Package

As with most integrated circuits,the LM3708and LM3709are sensitive to exposure from visible and infrared (IR)light radiation.Unlike a plastic encapsulated IC,the micro SMD package has very limited shielding from light,and some sensitivity to light reflected from the surface of the PC board or long wavelength IR entering the die from the side may be experienced.This light could have an unpredictable affect on the electrical performance of the IC.Care should be taken to shield the device from direct exposure to bright visible or IR light during operation.

Micro SMD Mounting

The micro SMD package requires specific mounting tech-niques which are detailed in National Semiconductor Appli-cation Note AN-1112.Referring to the section Surface Mount Technology (SMT)Assembly Considerations ,it should be noted that the pad style which must be used with the 9-pin package is the NSMD (non-solder mask defined)type.

For best results during assembly,alignment ordinals on the PC board may be used to facilitate placement of the micro SMD device.

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Timing Diagrams LM3708/LM3709

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Typical Application Circuit

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Physical Dimensions

inches (millimeters)

unless otherwise noted

NOTES:UNLESS OTHERWISE SPECIFIED 1.EPOXY COATING

2.63Sn/37Pb EUTECTIC BUMP

3.RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.

4.PIN 1IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION.REMAINING PINS ARE NUMBERED COUNTER CLOCKWISE.

5.XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1IS PACKAGE WIDTH,X2IS PACKAGE LENGTH AND X3IS PACKAGE HEIGHT.

6.NO JEDEC REGISTRATION AS OF AUG.1999.

9bump micro SMD Package NS Package Number BPA09FFB

The dimensions of X1,X2and X3are given below

X1=1.412mm X2=1.412mm X3=0.850mm

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION.As used herein:1.Life support devices or systems are devices or systems which,(a)are intended for surgical implant into the body,or (b)support or sustain life,and whose failure to perform when properly used in accordance with instructions for use provided in the labeling,can be reasonably expected to result in a significant injury to the user.

2.A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system,or to affect its safety or effectiveness.

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Tel:81-3-5639-7560Fax:81-3-5639-7507

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LM3708/LM3709Microprocessor Supervisory Circuits with Low Line Output,Manual Reset and Watchdog Timer

National does not assume any responsibility for use of any circuitry described,no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.