MICREL MIC2779H-2BM5, MIC2779L-1BM5, MIC2779L-2BM5, MIC2779H-1BM5 Datasheet
MIC2779 Micrel
V
MIC2779
Voltage Monitor with Adjustable Hysteresis
Preliminary Information
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 independently, 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 downstream 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
supplied 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 requiring open-drain output, see
MIC2778/MIC833
• Immune to brief power supply transients
• 5-lead SOT-23 package
Applications
• PDAs
• Pagers
• Cordless phones
• Consumer electronics
• Embedded controllers
• Personal electronics
T ypical Application
MIC5207-3.0BM5
OUT
BYP
GND
470pF
Li-Ion
Cell
604k
1%
56k
1%
340k
1%
MIC2779L
VDD
LTH
HTH
V
= 3.6V
BAT(hi)
= 3.1V
V
BAT(lo)
/RST
GND
IN
EN
Cellular Telephone Battery Monitor
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
June 2000 1 MIC2779
OUT
3.0V
4.7µF
MIC2779 Micrel
Ordering Information
Part Number Marking Output Polarity Accuracy Temperature Range Package
MIC2779H-2BM5 UPA2 Active-High RST 2% –40°C to +85°C SOT-23-5
MIC2779H-1BM5 UPA1 Active-High RST 1% –40°C to +85°C SOT-23-5
MIC2779L-2BM5 UPB2 Active-Low /RST 2% –40°C to +85°C SOT-23-5
MIC2779L-1BM5 UPB1 Active-Low /RST 1% –40°C to +85°C SOT-23-5
Pin Configuration
GND
2
HTH
13
LTH
45
VDDRST
SOT-23-5 (M5)
“H” Version
LTH
45
SOT-23-5 (M5)
“L” Version
GND
2
HTH
13
VDD/RST
Pin Description
Pin Number Pin Number Pin Name Pin Function
MIC2779H MIC2779L
1 1 HTH High-Voltage Theshold (Input): Analog input to a comparator. When the
level on this pin initially rises above V
/RST remains low or RST remains high for a minimum of 140ms.
2 2 GND Ground
3 3 LTH Low-Voltage Threshold (Input): Analog input to a comparator. This is the
voltage monitor input assigned to detect a low voltage condition. When the
level on this pin falls below V
is latched until V
HTH
> V
REF
, /RST or RST is asserted and the condition
REF
.
4 RST Reset (Output): Push-pull output. This output is asserted and latched when
V
<V
LTH
until V
mined by the part number suffix. See ordering information.
, indicating a low voltage condition. This state remains latched
REF
HTH
> V
. The polarity of this signal (active-high or low) is deter
REF
4 /RST Reset (Output): Push-pull output. This output is asserted and latched when
<V
V
LTH
until V
, indicating a low voltage condition. This state remains latched
REF
HTH
> V
. The polarity of this signal (active-high or low) is deter
REF
mined by the part number suffix. See ordering information.
5 5 VDD Power Supply (Input): Independent supply input for internal circuitry.
, the delay generator cycles and the
REF
MIC2779 2 June 2000
MIC2779 Micrel
Absolute Maximum Ratings (Note 1)
Supply Voltage (V
Input Voltages (V
/RST, RST Output Current (I
Storage Temperature (TS) .......................–65°C to +150°C
) ..................................... –0.3V to +7V
DD
, V
LTH
HTH
, V
/RST
/RST
, V
), (I
) ..... –0.3V to +7V
RST
)...................20mA
RST
Operating Ratings (Note 2)
Supply Voltage (V
Input Voltages (V
Ambient Temperature Range (T
Package Thermal Resistance ...............................256°C/W
) .................................. +1.5V to +5.5V
DD
, V
LTH
HTH
, V
, V
/RST
) ............. –40°C to +85°C
A
)..–0.3V to +6.0V
RST
ESD Rating, Note 3 ......................................................2kV
Electrical Characteristics
1.5V ≤ VDD ≤ 5.5V; TA = +25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol Parameter Condition Min Typ Max Units
I
DD
I
LTH, IHTH
V
REF
t
D
t
RESET
V
OL
V
OH
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Note 4. VDD operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to VDD = 1.2V.
Supply Current /RST, RST not asserted 1 2 µA
Input Leakage Current 5pA
10 nA
Reference Voltage 1.240 V
MIC2779H/L-2 1.215 1.265 V
MIC2779H/L-1 1.228 1.252 V
Propagation Delay V
LTH
V
REF(min)
= V
REF(max)
– 100mV
+100mV to 5 µs
Reset Pulse Width 140 420 ms
Reset Output Low Voltage /RST asserted or RST not asserted,
I
= 1.6mA, VDD ≥ 1.6V 0.3 V
SINK
/RST asserted or RST not asserted,
I
= 100µA, VDD ≥ 1.2V, 0.4 V
SINK
Reset Output High Voltage /RST not asserted or RST asserted,
I
SOURCE
= 500µA, VDD ≥ 1.6V 0.8V
DD
V
/RST not asserted or RST asserted,
I
SOURCE
= 50µA, VDD ≥ 1.2V, 0.8V
DD
V
Timing Diagram
V
BATT
V
HTH
LTH
V
A
0V
V
/RST
RST
OH
V
OL
V
OH
V
OL
Propagation delays not shown for clarity.
Note A. The MIC2779 ignores very brief transients.
V
V
t
RST
See “Applications Information” for details.
June 2000 3 MIC2779
A
t
RST
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