Rainbow-electronics LM3824 Instrukcja Użytkownika Strona 1

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LM3824
Precision Current Gauge IC with Internal Zero Ohm
Sense Element and PWM Output
General Description
The LM3824 Current Gauge provides easy to use precision
current measurement with virtually zero insertion loss (typi-
cally 0.003). The LM3824 is used for high-side sensing.
A Delta Sigma analog to digital converter is incorporated to
precisely measure the current and to provide a current aver-
aging function. Current is averaged over 6 msec time peri-
ods in order to provide immunity to current spikes. The ICs
have a pulse-width modulated (PWM) output which indicates
the current magnitude and direction. The shutdown pin can
be used to inhibit false triggering during start-up, or to enter
a low quiescent current mode.
The LM3824 is factory-set in two different current options.
The sense range is −1.0A to +1.0A or −2.0A to +2.0A. The
sampling interval for this part is 6ms. If a more precise mea-
surement is required, please refer to LM3822 datasheet.
Key Specifications
n Ultra low insertion loss (0.003)
n 2V to 5.5V supply range
n
±
3% accuracy at room temperature for the 1A device
(includes accuracy of the internal sense element)
n Low quiescent current in shutdown mode
(typically 1.8 µA)
n 6 msec sampling interval
n In MSOP-8 Package
Features
n No external sense element required
n PWM output indicates the current magnitude and
direction
n PWM output is easily interfaced with microprocessors
and controllers
n Precision ∆Σ current-sense technique
n Low temperature sensitivity
n Internal filtering rejects false trips
n Internal Power-On-Reset (POR)
n DC Offset is less than 8 mA for 1A part
Applications
n Battery charge/discharge gauge
n Motion control diagnostics
n Power supply load monitoring and management
n Resettable smart fuse
Connection Diagram
DS200007-1
Top View
LM3824 for High-Side Sensing
July 2000
LM3824 Precision Current Gauge IC with Internal Zero Ohm Sense Element and PWM Output
© 2000 National Semiconductor Corporation DS200007 www.national.com
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Podsumowanie treści

Strona 1 - Sense Element and PWM Output

LM3824Precision Current Gauge IC with Internal Zero OhmSense Element and PWM OutputGeneral DescriptionThe LM3824 Current Gauge provides easy to use pr

Strona 2 - Ordering Information

Look-Up TablesThe following tables show how to convert the duty cycle ofthe PWM output to a current value, and vice versa. Thequantization error of1⁄2

Strona 3

Timing DiagramDS200007-11Duty cycle of the PWM waveform during any sampling interval indicates the current magnitude (average) and direction during th

Strona 4

Physical Dimensions inches (millimeters) unless otherwise notedLIFE SUPPORT POLICYNATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENT

Strona 5

Ordering InformationOrder No.*SenseRangeSamplingInterval*SensingMethodNSPackageNumberPackageTypeSupplied As:LM3824MM-1.0±1.0A 6 ms High-side MUA08A MS

Strona 6 - DS200007-22

Absolute Maximum Ratings (Note 1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distribut

Strona 7

Common Device Parameters (Continued)Unless otherwise specified, VDD= 3.6V for the following specifications. Supply bypass capacitor is 1 µF and filter

Strona 8 - Product Operation

Typical Performance Characteristics Supply bypass capacitor is 0.1 µF and filter capacitor is 0.1 µF.Measured Current vs Actual Current(LM3824-1.0)DS2

Strona 9 - Accuracy

Typical Performance Characteristics Supply bypass capacitor is 0.1 µF and filter capacitor is0.1 µF. (Continued)Note 10: These curves represent a stat

Strona 10 - Look-Up Tables

Typical Application Circuits In the application circuits, the 0.1 µF ceramic capacitor between pins 1 and 2is used for bypassing, and the 0.1 µF ceram

Strona 11 - Timing Diagram

Product OperationThe current is sampled by the delta-sigma modulator, as il-lustrated inFigure 4. The pulse density output of thedelta-sigma modulator

Strona 12 - NS Package Number MUA08A

PWM Output and CurrentAccuracyOffsetThe PWM output is quantized to 128 levels. Therefore, theduty cycle can change only in increments of 1/128.There i

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