Rainbow-electronics LM3822 Bedienungsanleitung

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LM3822
Precision Current Gauge IC with Internal Zero Ohm
Sense Element and PWM Output
General Description
The LM3822 Current Gauge provides easy to use precision
current measurement with virtually zero insertion loss (typi-
cally 0.003). The LM3822 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 av-
eraging function. Current is averaged over 50 msec time
periods in order to provide immunity to current spikes. The
ICs have a pulse-width modulated (PWM) output which indi-
cates 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 LM3822 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 50ms. If faster sampling is
desired, please refer to the data sheet for the part number
LM3824.
Key Specifications
n Ultra low insertion loss (typically 0.003)
n 2V to 5.5V supply range
n
±
2% 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 50 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 1 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
10124901
Top View
LM3822 for High-Side Sensing
November 2000
LM3822 Precision Current Gauge IC with Internal Zero Ohm Sense Element and PWM Output
© 2004 National Semiconductor Corporation DS101249 www.national.com
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Inhaltsverzeichnis

Seite 1 - Sense Element and PWM Output

LM3822Precision Current Gauge IC with Internal Zero OhmSense Element and PWM OutputGeneral DescriptionThe LM3822 Current Gauge provides easy to use pr

Seite 2 - Ordering Information

PWM Output and CurrentAccuracyOFFSETThe PWM output is quantized to 1024 levels. Therefore, theduty cycle can change only in increments of 1/1024.There

Seite 3

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

Seite 4

Timing Diagram10124911Duty cycle of the PWM waveform during any sampling interval indicates the current magnitude (average) and direction during the p

Seite 5 - 10124924 10124925

Physical Dimensions inches (millimeters) unless otherwise noted8-Lead MSOPSee Ordering Information table for Order NumbersNS Package Number MUA08ANati

Seite 6

Ordering InformationOrder No.*SenseRangeSamplingInterval*SensingMethodNSPackageNumberPackageTypeSupplied As:LM3822MM-1.0±1.0A 50 ms High-side MUA08A M

Seite 7 - 10124907

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

Seite 8

Electrical Characteristics Typical numbers are at 25˚C and represent the most likely parametric norm.Specifications in standard type face are for TJ=

Seite 9 - Product Operation

Typical Performance Characteristics Supply bypass capacitor is 0.1 µF and filter capacitor is0.1 µF.Measured Current vs Actual Current(LM3822-1.0)Meas

Seite 10 - Accuracy

Typical Performance Characteristics Supply bypass capacitor is 0.1 µF and filter capacitor is0.1 µF. (Continued)Operating Current vs Temperature Shutd

Seite 11 - 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

Seite 12 - Timing Diagram

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

Seite 13 - NS Package Number MUA08A

Product OperationThe current is sampled by the delta-sigma modulator, asillustrated in Figure 4. The pulse density output of the delta-sigma modulator

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