MIC2779H-2BM5TR [MICREL]
Power Supply Support Circuit, Adjustable, 1 Channel, PDSO5, SOT-23, 5 PIN;
| 型号： | MIC2779H-2BM5TR |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | Power Supply Support Circuit, Adjustable, 1 Channel, PDSO5, SOT-23, 5 PIN 光电二极管 |
| 文件： | 总8页 (文件大小：54K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC2779
Voltage Monitor with Adjustable Hysteresis
Preliminary Information
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 indepen-
dently,allowingforwidehysteresis.Voltagedetectionthresh-
olds are accurate to 2%.
Ifthebatteryvoltagefallsbelowthelow-voltagethreshold,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.
• Immune to brief power supply transients
• 5-lead SOT-23 package
Applications
• PDAs
• Pagers
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.
• Cordless phones
• Consumer electronics
• Embedded controllers
• Personal electronics
A high-precision 1% grade is available. The MIC2779 is
supplied in Micrel’s IttyBitty™ 5-lead 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%
V
BAT(hi) = 3.6V
VBAT(lo) = 3.1V
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
MIC2779
Micrel
Ordering Information
Part Number
Marking
UPA2
UPA1
UPB2
UPB1
Output Polarity Accuracy
Temperature Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
SOT-23-5
SOT-23-5
SOT-23-5
SOT-23-5
MIC2779H-2BM5
MIC2779H-1BM5
MIC2779L-2BM5
MIC2779L-1BM5
Active-High RST
Active-High RST
Active-Low /RST
Active-Low /RST
2%
1%
2%
1%
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)
“L” Version
SOT-23-5 (M5)
“H” Version
Pin Description
Pin Number
MIC2779H
Pin Number
MIC2779L
Pin Name
Pin Function
High-Voltage Theshold (Input): Analog input to a comparator. When the
1
1
HTH
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
.
4
RST
/RST
VDD
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.
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
2
June 2000
MIC2779
Micrel
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
MIC2779H/L-1
1.215
1.228
1.265
1.252
V
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,
ISINK = 1.6mA, VDD ≥ 1.6V
/RST asserted or RST not asserted,
ISINK = 100µA, VDD ≥ 1.2V,
V
VOH
Reset Output High Voltage
/RST not asserted or RST asserted,
ISOURCE = 500µA, VDD ≥ 1.6V
0.8VDD
0.8VDD
V
/RST not asserted or RST asserted,
ISOURCE = 50µA, VDD ≥ 1.2V,
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. operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to V = 1.2V.
V
DD
DD
Timing Diagram
A
VHTH
VLTH
0V
VBATT
A
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.
June 2000
3
MIC2779
MIC2779
Micrel
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
internal 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 being
replaced, or being recharged above a second higher pro-
grammed 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 com-
ponent. See “Timing Diagram.”
Delay
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.
/RST, RST Low Output
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
4
June 2000
MIC2779
Micrel
Once R3 is determined, the equation for V
to determine R2. A single lithium-ion cell should not be
discharged below 2.5V. Many applications limit the drain to
can be used
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)
of the two remaining resistor values.
R1+R2 +R3
V
= V
REF
BAT(lo)
R2 +R3
1MΩ
V
= 3.1V = 1.24
BAT(lo)
R2 + 344k
The high-voltage threshold is calculated using:
R2 = 56kΩ
R1+R2 +R3
V
= V
REF
BAT(hi)
R1= 1MΩ −R2 −R3
R1= 600kΩ
R3
where, for both equations:
The accuracy of the resistors can be chosen based upon the
accuracy required by the system.
VREF = 1.240V
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 = R
A value such as 1MΩ for R
because it draws minimum battery current but has no mea-
surable effect on accuracy.
Input Transients
The MIC2779 is inherently immune to very short negative-
.
TOTAL
going“glitches.”VerybrieftransientsmayexceedtheV
BAT(lo)
is a reasonable value
TOTAL
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 duration
for a given amount of threshold overdrive that will not gener-
ate a reset.
Whenworkingwithlargeresistors, asmallamountofleakage
current can cause voltage offsets that degrade system accu-
racy. The maximum recommended total resistance from
V
to ground is 3MΩ.
BAT
Input Transient
VBATT
Response
140
MIC2779
120
100
80
60
40
20
0
604k
R1
R2
R3
VDD
LTH
/RST
RST
1%
56k
1%
HTH GND
340k
1%
1
10
100
1000
–V
Figure 1. Example Circuit
RESET COMP. OVERDRIVE, V
(mV)
LTH
REF
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
V
= 1.24
BAT(hi)
R3
R3 = 344kΩ
June 2000
5
MIC2779
MIC2779
Micrel
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)
SOT-23-5 (M5)
MIC2779
6
June 2000
MIC2779
Micrel
June 2000
7
MIC2779
MIC2779
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com
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.
© 2000 Micrel Incorporated
MIC2779
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June 2000
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