Rainbow Electronics LM3822 - Manual

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
Ω). 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 Ω)
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