MIC2778
Micrel
MIC2778
Voltage Monitor with Adjustable Hysteresis
General Description
The MIC2778 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) 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
not requiring built-in delay, see MIC841.
The IC’s power supply input is separate from the detector
inputs, allowing the MIC2778 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 MIC2778 is sup-
plied in Micrel’s IttyBitty™ 5-lead 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 not requiring built-in delay, see MIC841
• Immune to brief power supply transients
• 5-lead SOT-23 package
Applications
•
•
•
•
•
•
PDAs
Pagers
Cordless phones
Consumer electronics
Embedded controllers
Personal electronics
Ordering Information
Part Number
Standard
MIC2778-2BM5
MIC2778-1BM5
Marking
UFB
UFA
Pb-Free
MIC2778-2YM5
MIC2778-1YM5
Marking
UFB*
UFA*
2%
1%
-40°C to +85°C
-40°C to +85°C
SOT-23-5
SOT-23-5
Accurary
Temperature Range
Package
* Underscore indicates a Pb-Free part.
Typical Application
MIC5207-3.0BM5
Li-Ion
Cell
604k
1%
56k
1%
340k
1%
MIC2778
VDD
LTH
HTH
R ST
GND
IN
100k
OUT
BYP
GND
V
OUT
3.0V
470pF
4.7µF
EN
V
BAT(hi)
= 3.6V
V
BAT(lo)
= 3.1V
Cellular Telephone Battery Monitor
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
January 2005
1
M9999-011405
MICREL [ MICREL SEMICONDUCTOR ]
