19-2061; Rev 0; 5/01
AILABLE
ION KIT AV
EVALUAT
Simple, Efficient, 1-Cell Li+ Pulse Charger
General Description
The MAX1879 single-cell lithium-ion (Li+) battery charger
utilizes an efficient pulse-charging architecture to minimize
power dissipation in portable devices. This architecture
combines the efficiency of switch-mode chargers with the
simplicity and low cost of linear chargers. This simple
device, in conjunction with a current-limited wall cube and
a PMOS transistor, allows safe and fast charging of a sin-
gle Li+ cell.
The MAX1879 initiates charging in one of three ways: bat-
tery insertion, charger power-up, or toggling the THERM
pin. Key safety features include continuous voltage and
temperature monitoring, a preset charger time-out, and an
8mA precharge current mode to charge near-dead cells.
Automatic detection of input power removal shuts down
the device, minimizing current drain from the battery. An
overall system accuracy of 0.75% ensures that the cell
capacity is fully utilized without cycle life degradation.
The MAX1879 is offered in a space-saving 8-pin µMAX
package. An evaluation kit (MAX1879EVKIT) is available
to help reduce design time.
o
Simple Design Minimizes Heat
o
Low Component Count, No Inductor
o
Battery-Full Indicator
o
0.75% Accurate Battery Regulation
o
1.5µA (max) Battery Current Drain with Wall Cube
Removed
o
Restart Charging at 4.0V
o
Continuous Overvoltage and Overtemperature
Protection
o
Safely Precharges Near-Dead Cells
o
Automatic Power-Down when Power Source is
Removed
o
Charges 1 Cell from as Low as 4.5V
o
Pin-Compatible Upgrade to MAX1679
Features
MAX1879
Applications
Single-Cell Li+ Powered Portables
Self-Charging Battery Packs
PDAs
Cell Phones
Cradle Chargers
PART
MAX1879EUA
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8-µMAX
Pin Configuration
TOP VIEW
CURRENT-
LIMITED
AC WALL
ADAPTER
LED
Typical Operating Circuit
IN
GATE
CHG
1
2
8
7
BATT
THERM
GND
ADJ
MAX1879
3
6
5
TSEL
4
IN
CHG
GATE
BATT
1-CELL
Li+
BATTERY
MAX1879
PULSE WIDTH
SELECT INPUT
TSEL
THERM
THERMISTOR
GND
ADJ
µMAX
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Simple, Efficient, 1-Cell Li+ Pulse Charger
MAX1879
ABSOLUTE MAXIMUM RATINGS
IN,
CHG,
GATE to GND..........................................-0.3V to +26V
BATT, TSEL, THERM, ADJ to GND...........................-0.3V to +6V
GATE to IN................................................................-6V to +0.3V
THERM, ADJ to BATT...............................................-6V to +0.3V
GATE Continuous Current ................................................ -10mA
Continuous Power Dissipation (TA = +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C) ............ 330mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................ +300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
IN
= V
CHG
= +10V, V
BATT
= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND,
T
A
= 0°C to
+85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Voltage (Note 1)
Undervoltage Lockout Trip Point
Undervoltage Lockout Trip-Point
Hysteresis
Fast-Charge Qualification
Threshold
Fast-Charge Restart Threshold
Fast-Charge Reset Threshold
Delay
Precharge Source Current
BATT Regulation Voltage
BATT Regulation Adjust Range
ADJ Source Impedance
ADJ Output Voltage
BATT Removal Detection
Threshold
BATT Removal Detection
Threshold Hysteresis
BATT Input Current (Note 4)
BATT Input Current, Fast-Charge
State
BATT Input Current, Done State
IN Input Current, Fast-Charge
State
IN Input Current, Done State
Timer Accuracy
CHG
Output Leakage Current
CHG
Output Sink Current
V
CHG
= 22V,
CHG
= high
V
CHG
= 1.0V,
CHG
= low
I
BATT
I
BATT
I
IN
I
IN
No load on ADJ
BATT rising
BATT falling
V
IN
≤
V
BATT
- 0.3V
V
BATT
= 4.0V
V
BATT
= 4.25V, V
IN
present
V
BATT
= 4.0V, V
IN
= 4.0V
V
BATT
= 4.25V, V
IN
= 22V
-10
-1
4
5
SYMBOL
V
IN
BATT rising
BATT falling
BATT rising, transition from precharge to
full current
BATT falling, transition from Done to
Prequalification state (Note 2)
(Note 3)
V
BATT
= 2V
5
4.1685
4.0
9.8
1.393
4.875
10
1.400
5
125
0.1
900
85
50
700
1.5
1500
200
500
1200
+10
+1
6
2.425
3.92
CONDITIONS
External PMOS FET off
MIN
4.4
2.1
2.2
60
2.5
4.00
1
8
4.2000
12
4.2315
4.2
10.2
1.407
5.125
2.575
4.08
TYP
MAX
22
2.3
UNITS
V
V
mV
V
V
ms
mA
V
V
kΩ
V
V
mV
µA
µA
µA
µA
µA
%
µA
mA
2
_______________________________________________________________________________________
Simple, Efficient, 1-Cell Li+ Pulse Charger
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
CHG
= +10V, V
BATT
= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND,
T
A
= 0°C to
+85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
THERM Sense Current (for hot
qualification)
THERM Sense Current (for cold
qualification)
THERM Sense Voltage Trip Point
GATE Source Current
GATE Sink Current
GATE Drive Current at Battery
Removal
V
IN
= 10V, V
GATE
= 8V
V
IN
= 10V, V
GATE
= 8V
V
BATT
= 5.1V, gate driven high
SYMBOL
CONDITIONS
MIN
346
47.8
1.379
75
19
18
TYP
352.9
48.8
1.40
100
25
40
MAX
360
49.8
1.421
125
31
60
UNITS
µA
µA
V
µA
µA
mA
MAX1879
ELECTRICAL CHARACTERISTICS
(V
IN
= V
CHG
= +10V, V
BATT
= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GN
, TA
= -40°C to
+85°C,
unless otherwise noted.) (Note 5)
PARAMETER
Input Voltage (Note 1)
Undervoltage Lockout Trip Point
Fast-Charge Qualification
Threshold
Fast-Charge Restart Threshold
Precharge Source Current
BATT Regulation Voltage
BATT Regulation Adjust Range
ADJ Source Impedance
ADJ Output Voltage
BATT Removal Detection
Threshold
BATT Input Current (Note 4)
BATT Input Current, Fast-Charge
State
BATT Input Current, Done State
IN Input Current, Fast-Charge
State
IN Input Current, Done State
CHG
Output Leakage Current
CHG
Output Sink Current
I
BATT
I
BATT
I
IN
I
IN
No load on ADJ
BATT rising
V
IN
≤
V
BATT
- 0.3V
V
BATT
= 4.0V
V
BATT
= 4.25V, V
IN
present
V
BATT
= 4.0V, V
IN
= 4.0V
V
BATT
= 4.25V, V
IN
= 22V
V
CHG
= 22V,
CHG
= high
V
CHG
= 1.0V,
CHG
= low
-1
4
SYMBOL
V
IN
BATT rising
BATT rising, transition from precharge to
full current
BATT falling, transition from Done to
Prequalification state (Note 2)
V
BATT
= 2V
CONDITIONS
External PMOS FET off
MIN
4.6
2.05
2.35
3.88
4.5
4.137
4.0
9.8
1.383
4.85
MAX
22
2.35
2.65
4.12
12
4.263
4.2
10.2
1.417
5.15
1.5
1500
300
600
1500
+1
6
UNITS
V
V
V
V
mA
V
V
kΩ
V
V
µA
µA
µA
µA
µA
µA
mA
_______________________________________________________________________________________
3
Simple, Efficient, 1-Cell Li+ Pulse Charger
MAX1879
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
CHG
= +10V, V
BATT
= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND,
TA
= -40°C to +85°C,
unless otherwise noted.) (Note 5)
PARAMETER
THERM Sense Current (for hot
qualification)
THERM Sense Current (for cold
qualification)
THERM Sense Voltage Trip Point
GATE Source Current
GATE Sink Current
GATE Drive Current at Battery
Removal
V
IN
= 10V, V
GATE
= 8V
V
IN
= 10V, V
GATE
= 8V
V
BATT
= 5.1V, gate driven high
SYMBOL
CONDITIONS
MIN
342
47.3
1.358
60
15
15
MAX
363
50.3
1.442
140
35
90
UNITS
µA
µA
V
µA
µA
mA
Note 1:
The input voltage range is specified with the external PMOS FET off. When charging, the PMOS FET turns on, and the input
voltage (the output voltage of the current-limited source) drops to very near the battery voltage. When the PFET is on, V
IN
may be as low as 2.5V.
Note 2:
Restart Threshold tracks battery regulation voltage adjustment.
Note 3:
Glitches less than 1ms do not cause a restart.
Note 4:
This current is less than 1.5µA, even if an external R
ADJ
resistor is connected from ADJ to GND.
Note 5:
Specifications to -40°C are guaranteed by design and not production tested.
4
_______________________________________________________________________________________
Simple, Efficient, 1-Cell Li+ Pulse Charger
Typical Operating Characteristics
(V
IN
=
CHG
= +10V, V
BATT
= +4.2V, THERM = 10kΩ to GND, T
A
= +25°C, unless otherwise noted.)
MAX1879
NORMALIZED TIMER PERIOD
vs. AMBIENT TEMPERATURE
MAX1879 toc01
NORMALIZED BATTERY REGULATION
VOLTAGE vs. TEMPERATURE
NORMALIZED REGULATION VOLTAGE
1.0015
1.0010
1.0005
1.0000
0.9995
0.9990
0.9985
0.9980
0.9975
0.9970
NORMALIZED TO +25°C
MAX1879 toc02
PRECHARGE CURRENT
vs. INPUT VOLTAGE
8.8
PRECHARGE CURRENT (mA)
8.6
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0
V
BATT
= 2V
V
BATT
= 0
MAX1879 toc03
1.020
1.015
NORMALIZED TIMER PERIOD
1.010
1.005
1.000
0.995
0.990
0.985
0.980
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
NORMALIZED TO +25°C
1.0020
9.0
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
5
10
15
V
IN
(V)
20
25
Pin Description
PIN
1
2
NAME
IN
GATE
FUNCTION
Input Voltage from Current-Limited Voltage Source (+22V max). Bypass to GND with a 0.1µF capacitor.
Gate Drive for External PMOS Pass Element. The PMOS device should have a V
GS
threshold less than
2.5V. See
Selecting External Components.
Charge Status Indication. A
CHG
low indicates that the MAX1879 is charging a battery.
CHG
goes high
when the on/off duty cycle falls to 1/8, indicating that the battery is charged to approximately 95% of full
capacity.
CHG
is an open-drain current-limited N-channel MOSFET suitable for directly driving an LED.
Connect a pullup resistor to the logic supply to generate a logic-level signal.
CHG
blinks at 2Hz during the
Prequalification state (2.2V < V
BATT
< 2.5V) and during a temperature fault.
Minimum ON/OFF Pulse Width Selection (Table 2)
Battery Regulation Voltage Adjustment. Bypass to GND with a 1000pF capacitor. Connect a resistor from
ADJ to GND to reduce the nominal +4.200V regulation set point. See
Adjusting the Battery Regulation
Voltage.
Ground. See
Layout Guidelines
for information on system grounding. Connect the battery’s negative
terminal to GND.
Thermistor Temperature-Sensor Input. Connect an NTC thermistor (10kΩ at +25°C) from THERM to GND to
allow prequalification of the cell temperature for fast-charge. Replace the thermistor with a 10kΩ resistor if
temperature sensing is not required.
Cell Voltage Monitor Input, Precharge Current Output, and MAX1879 Power Source. Connect BATT to the
positive terminal of a single Li+ cell. Bypass BATT with a capacitor to ground (1.5µF per amp of charge
current).
3
CHG
4
5
TSEL
ADJ
6
GND
7
THERM
8
BATT
_______________________________________________________________________________________
5
微控制器 MCU
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
