MIC2778_05 Datasheet, PDF (1/6 Pages) Micrel Semiconductor – Voltage Monitor with Adjustable Hysteresis

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
Marking Pb-Free
MIC2778-2BM5
UFB
MIC2778-1BM5
UFA
* Underscore indicates a Pb-Free part.
MIC2778-2YM5
MIC2778-1YM5
Marking
UFB*
UFA*
Accurary
2%
1%
Temperature Range
-40°C to +85°C
-40°C to +85°C
Package
SOT-23-5
SOT-23-5
Typical Application
Li-Ion
Cell
604k
1%
56k
1%
MIC2778
VDD RST
LTH
HTH GND
MIC5207-3.0BM5
IN
100k
EN
OUT
BYP
GND
470pF
V_OUT
3.0V
4.7µF
340k
1%
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 [phone] • fax + 1 [phone] • http://www.micrel.com
January 2005
1
M9999-011405