MIC2779H-1BM5TR [ROCHESTER]
1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, SOT-23, 5 PIN;
| 型号： | MIC2779H-1BM5TR |
| 厂家： | 
Rochester Electronics |
| 描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, SOT-23, 5 PIN 光电二极管 |
| 文件： | 总7页 (文件大小：828K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC2779
Voltage Monitor with Adjustable Hysteresis
General Description
Features
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.
• 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
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.
Internallogicpreventstheoutputfromchatteringduetobattery
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.
• Immune to brief power supply transients
• 5-pin SOT-23 package
Applications
• PDAs
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.
• Pagers
• Cordless phones
• Consumer electronics
• Embedded controllers
• Personal electronics
Ahigh-precision 1% grade is available. The MIC2779 is sup-
plied in Micrel’s IttyBitty™ 5-pin SOT-23-5 package.
Typical Application
VOUT
3.0V
MIC5207-3.0BM5
OUT
BYP
GND
IN
470pF
MIC2779L
Li-Ion
Cell
4.7µF
604k
1%
VDD
LTH
EN
/RST
56k
1%
HTH GND
340k
1%
VBAT(hi)= 3.6V
VBAT(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 2006
1
MIC2779
MIC2779
Micrel, Inc.
Ordering Information
Part Number
Marking Pb-Free
Output Polarity Accuracy Temperature Range
Package
Standard
Marking
UPA2
MIC2779H-2BM5
MIC2779H-1BM5
MIC2779L-2BM5
MIC2779L-1BM5
UPA2
UPA1
UPB2
UPB1
MIC2779H-2YM5
Active-High RST
Active-High RST
Active-Low /RST
Active-Low /RST
2%
1%
2%
1%
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
SOT-23-5
SOT-23-5
SOT-23-5
SOT-23-5
MIC2779H-1YM5
MIC2779L-2YM5
MIC2779L-1YM5
UPA1
UPB2
UPB1
Pin Configuration
LTH GND HTH
LTH GND HTH
3
2
1
3
2
1
4
5
4
5
RST
VDD
/RST
VDD
SOT-23-5 (M5)
“H” Version
SOT-23-5 (M5)
“L” Version
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 VREF, the delay generator cycles and the
/RST remains low or RST remains high for a minimum of 140ms.
2
3
2
3
GND
LTH
Ground
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 VREF, /RST or RST is asserted and the condition
is latched until VHTH > VREF
Reset (Output): Push-pull output. This output is asserted and latched when
LTH <VREF, indicating a low voltage condition. This state remains latched
until VHTH > VREF. The polarity of this signal (active-high or low) is deter
mined by the part number suffix. See ordering information.
.
4
RST
/RST
VDD
V
4
5
Reset (Output): Push-pull output. This output is asserted and latched when
VLTH <VREF, indicating a low voltage condition. This state remains latched
until VHTH > VREF. The polarity of this signal (active-high or low) is deter
mined by the part number suffix. See ordering information.
5
Power Supply (Input): Independent supply input for internal circuitry.
MIC2779
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January 2006
MIC2779
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (V ).......................................–0.3V to +7V
Supply Voltage (V ) .................................. +1.5V to +5.5V
DD
DD
Input Voltages (V , V
, V
, V
)........–0.3V to +7V
Input Voltages (V , V
, V
, V
).....–0.3V to +6.0V
LTH
HTH
/RST RST
LTH
HTH
/RST RST
/RST, RST Output Current (I
), (I
).................... 20mA
Ambient Temperature Range (T ) .............. –40°C to +85°C
/RST
RST
A
Storage Temperature (T ) ........................ –65°C to +150°C
Package Thermal Resistance................................256°C/W
S
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
1
Max
2
Units
µA
pA
nA
V
IDD
Supply Current
Input Leakage Current
/RST, RST not asserted
ILTH, HTH
I
5
10
VREF
Reference Voltage
Propagation Delay
1.240
5
MIC2779H/L-2
1.215
1.228
1.265
1.252
V
MIC2779H/L-1
V
tD
VLTH = VREF(max) +100mV to
µs
VREF(min) – 100mV
tRESET
VOL
Reset Pulse Width
140
420
0.3
0.4
ms
V
Reset Output Low Voltage
/RST asserted or RST not asserted,
SINK = 1.6mA, VDD ≥ 1.6V
/RST asserted or RST not asserted,
SINK = 100µA, VDD ≥ 1.2V,
/RST not asserted or RST asserted,
SOURCE = 500µA, VDD ≥ 1.6V
/RST not asserted or RST asserted,
SOURCE = 50µA, VDD ≥ 1.2V,
I
I
V
VOH
Reset Output High Voltage
I
0.8VDD
0.8VDD
V
I
V
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.
Timing Diagram
A
VHTH
VBATT
VLTH
A
0V
tRST
tRST
VOH
VOL
V/RST
VOH
VOL
VRST
Propagation delays not shown for clarity.
Note A. The MIC2779 ignores very brief transients.
See “Applications Information” for details.
January 2006
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MIC2779
MIC2779
Micrel, Inc.
Functional Diagram
VDD
VBATT
Low-Voltage
Detect
LTH
HTH
VLO
R Q
/RST*
RST*
One Shot
High-Voltage
Detect
S
Q
VHI
Delay
Line
1.24V
Bandgap
Reference
MIC2779
GND
* Pinout and polarity vary by device type.
See ordering information table.
Trip Points
Functional Description
Battery voltage is monitored by a comparator via a voltage
divider network. The divided voltage is compared to an in-
ternal reference voltage. When the voltage at the LTH input
pin drops below the internal reference voltage, the output is
asserted. At this point, the voltage at HTH is assumed to be
below the reference voltage.
The MIC2779 monitors the voltage of a battery and detects
when it is discharged below a programmed level. Upon be-
ing replaced, or being recharged above a second higher
programmed trip point, the output remains low (MIC2779L)
or high (MIC2779H) for a minimum of 140ms and then sends
a reset signal to a microprocessor or other downstream
component. See “Timing Diagram.”
Delay
/RST, RST Low Output
At power-on or when the battery is replaced or recharged,
and the voltage at HTH exceeds the reference voltage, the
output is deasserted after a minimum delay of 140ms.
The output is a push-pull logic signal which is asserted when
the MIC2779 detects a low input voltage. The MIC2779L’s
/RST output is active-low; the MIC2779H’s RST output is
active-high.
MIC2779
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January 2006
MIC2779
Micrel, Inc.
Once R3 is determined, the equation for V
used to determine R2. A single lithium-ion cell should not be
discharged below 2.5V. Many applications limit the drain to
can be
Applications Information
Programming the Thresholds
BAT(lo)
The low-voltage threshold is calculated using:
3.1V. Using 3.1V for the V
threshold allows calculation
BAT(lo)
R1+R2 +R3
R2 +R3
of the two remaining resistor values.
V
= V
REF
BAT(lo)
1MΩ
V
= 3.1V = 1.24
BAT(lo)
R2 + 344k
The high-voltage threshold is calculated using:
R1+R2 +R3
R2 = 56kΩ
V
= V
REF
BAT(hi)
R3
R1=1MΩ −R2 −R3
R1= 600kΩ
where, for both equations:
= 1.240V
V
The accuracy of the resistors can be chosen based upon the
accuracy required by the system.
REF
In order to provide the additional criteria needed to solve
for the resistor values, the resistors can be selected such
that they have a given total value, that is, R1 + R2 + R3 =
Input Transients
The MIC2779 is inherently immune to very short negative-
R
. A value such as 1MΩ for R
is a reasonable
going“glitches.”VerybrieftransientsmayexceedtheV
TOTAL
TOTAL
BAT(lo)
value because it draws minimum battery current but has no
measurable effect on accuracy.
threshold without tripping the output.
As shown in Figure 2, the narrower the transient, the deeper
the threshold overdrive that will be ignored by the MIC2779.
The graph represents the typical allowable transient dura-
tion for a given amount of threshold overdrive that will not
generate a reset.
When working with large resistors, a small amount of leak-
age current can cause voltage offsets that degrade system
accuracy.The maximum recommended total resistance from
V
to ground is 3MΩ.
BAT
VBATT
Input Transient
Response
140
MIC2779
604k
120
100
80
60
40
20
0
R1
R2
R3
VDD
/RST
R ST
1%
LTH
56k
1%
HTH GND
340k
1%
Figure 1. Example Circuit
1
10
100
1000
RESET COMP. OVERDRIVE, VREF –VLTH(mV)
Once the desired trip points are determined, set the V
threshold first.
BAT(hi)
Figure 2. Input Transient Response
For example, use a total of 1MΩ = R1 + R2 + R3. For a typical
single-cell lithium ion battery, 3.6V is a good “high threshold”
because at 3.6V the battery is moderately charged. Solving
for R3:
1MΩ
R3
V
= 1.24
BAT(hi)
R3 = 344kΩ
January 2006
5
MIC2779
MIC2779
Micrel, Inc.
Package Information
1.90 (0.075) REF
0.95 (0.037) REF
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)
3.02 (0.119)
2.80 (0.110)
0.20 (0.008)
0.09 (0.004)
10°
0°
0.15 (0.006)
0.00 (0.000)
0.50 (0.020)
0.35 (0.014)
0.60 (0.024)
0.10 (0.004)
5-Pin SOT-23 (M5)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2000 Micrel, Inc.
MIC2779
6
January 2006
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