MIC2779_06 Datasheet, PDF (1/6 Pages) Micrel Semiconductor – Voltage Monitor with Adjustable Hysteresis

MIC2779
MIC2779
Micrel, Inc.
Voltage Monitor with Adjustable Hysteresis
General Description
The MIC2779 is a voltage monitor—uniquely designed to
detect two separate voltage thresholds—combined with a
delay generator and logic. It is designed for monitoring the
battery supply of portable digital systems, particularly PDAs,
pagers, and cellular telephones.
High- and low-voltage thresholds can be adjusted inde-
pendently, allowing for wide hysteresis. Voltage detection
thresholds are accurate to 2%.
If the battery voltage falls below the low-voltage threshold,
the output /RST or RST is asserted and latched, preventing
system operation until the battery is replaced or recharged.
Internal logic prevents the output from chattering due to battery
recovery or load removal. The output is asserted for 140ms
(minimum) when a fresh battery is inserted. For applications
requiring open-drain output, see MIC2778/MIC833.
The IC’s power supply input is separate from the detector
inputs, allowing the MIC2779 to be powered from a down-
stream supply, such a boost converter. Supply current is
extremely low (1µA, typical), making it ideal for portable
applications.
A high-precision 1% grade is available. The MIC2779 is sup-
plied in Micrel’s IttyBitty™ 5-pin SOT-23-5 package.
Features
• Optimized for PDAs, cellular telephones, pagers,
and other battery-powered devices
• Independently adjustable high- and
low-voltage thresholds
• Internal logic prevents battery-voltage-fluctuation chatter
• High ±2% voltage threshold accuracy; 1% available
• Built in 140ms (minimum) delay deglitches output
• Extremely low 1µA typical supply current
• For applications requiring open-drain output, see
MIC2778/MIC833
• Immune to brief power supply transients
• 5-pin SOT-23 package
Applications
• PDAs
• Pagers
• Cordless phones
• Consumer electronics
• Embedded controllers
• Personal electronics
Typical Application
Li-Ion
Cell
604k
1%
56k
1%
MIC2779L
VDD /RST
LTH
HTH GND
340k
1%
V_BAT(hi)= 3.6V
V_BAT(lo)= 3.1V
MIC5207-3.0BM5
IN
OUT
BYP ^470pF
EN _GND
V_{O U T}
3.0V
4.7µF
Cellular Telephone Battery Monitor
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com
January 2006
1
MIC2779