MIC2778-1BM5 MICREL [Micrel Semiconductor], MIC2778-1BM5 Datasheet

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MIC2778-1BM5

Manufacturer Part Number
MIC2778-1BM5
Description
Voltage Monitor with Adjustable Hysteresis Preliminary Information
Manufacturer
MICREL [Micrel Semiconductor]
Datasheet

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MIC2778-1BM5
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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 indepen-
dently, allowing for wide hysteresis. Voltage detection thresh-
olds 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 MIC833.
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 (1 A, typical), making it ideal for portable
applications.
A high-precision 1% grade is available. The MIC2778 is
supplied in Micrel’s IttyBitty™ 5-lead SOT-23-5 package.
Typical Application
IttyBitty™ is a trademark of Micrel, Inc.
October 1999
MIC2778
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
Li-Ion
Cell
Ordering Information
604k
1%
56k
1%
340k
1%
Part Number
MIC2778-2BM5
MIC2778-1BM5
Cellular Telephone Battery Monitor
V
V
VDD
LTH
HTH
BAT(hi)
BAT(lo)
MIC2778
= 3.6V
= 3.1V
GND
RST
Marking
1
UFB
UFA
100k
Features
• Optimized for PDAs, cellular telephones, pagers,
• Independently adjustable high- and
• Internal logic prevents battery-voltage-fluctuation chatter
• High 2% voltage threshold accuracy; 1% available
• Built in 140ms (minimum) delay deglitches output
• Extremely low 1 A typical supply current
• For applications not requiring built-in delay, see MIC833
• Immune to brief power supply transients
• 5-lead SOT-23 package
Applications
• PDAs
• Pagers
• Cordless phones
• Consumer electronics
• Embedded controllers
• Personal electronics
Voltage Monitor with Adjustable Hysteresis
and other battery-powered devices
low-voltage thresholds
MIC5207-3.0BM5
IN
EN
Accuracy
2%
1%
GND
OUT
BYP
Preliminary Information
470pF
MIC2778
Temperature Range
–40 C to +85 C
–40 C to +85 C
V
3.0V
4.7µF
OUT
SOT-23-5
SOT-23-5
Package
MIC2778
Micrel

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MIC2778-1BM5 Summary of contents

Page 1

... SOT-23 package Applications • PDAs • Pagers • Cordless phones • Consumer electronics • Embedded controllers • Personal electronics Ordering Information Part Number Marking Accuracy MIC2778-2BM5 UFB MIC2778-1BM5 UFA MIC5207-3.0BM5 IN MIC2778 100k 604k VDD RST EN 1% LTH 56k HTH ...

Page 2

... MIC2778 Pin Configuration Pin Description Pin Number Pin Name 1 HTH 2 GND 3 LTH 4 RST 5 VDD MIC2778 LTH GND HTH RST VDD SOT-23-5 (M5) Pin Function High-Voltage Theshold (Input): Analog input to a comparator. When the level on this pin initially rises above V REF RST remains low for a minimum of 140ms ...

Page 3

... RST asserted 100 A, V SINK V HTH V LTH RST V RSTH V RSTL Propagation delays not shown for clarity. Note A. The MIC2778 ignores very brief transients. See “Applications Information” for details. 3 (Note 2) ) .................................. +1.5V to +5. ............. –0.3V to +6.0V RST LTH HTH ) ............. – + Min Typ ...

Page 4

... Functional Description The MIC2778 monitors the voltage of a battery and detects when it is discharged below a programmed level. Upon being replaced, or being recharged above a second higher pro- grammed trip point, the output remains low for a minimum of 140ms and then sends a reset signal to a microprocessor or other downstream component ...

Page 5

... Some microprocessors have reset signal pins that are bidi- rectional, rather than input only. The Motorola 68HC11 family is one example. Because the MIC2778’s output is open drain, it can be connected directly to the processor’s reset pin using only the pull-up resistor normally required. See Figure 4. ...

Page 6

... MIC2778 Package Information 1.90 (0.075) REF 0.95 (0.037) REF 3.02 (0.119) 2.80 (0.110) 0.50 (0.020) 0.35 (0.014) MIC2778 1.75 (0.069) 3.00 (0.118) 1.50 (0.059) 2.60 (0.102) DIMENSIONS: MM (INCH) 1.30 (0.051) 0.90 (0.035 0.15 (0.006) 0.60 (0.024) 0.00 (0.000) 0.10 (0.004) SOT-23-5 (M5) 6 Micrel 0.20 (0.008) 0.09 (0.004) October 1999 ...

Page 7

... MIC2778 October 1999 7 Micrel MIC2778 ...

Page 8

... This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. MIC2778 + 1 (408) 944-0970 http://www ...

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