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PDF MAX1898 Data sheet ( Hoja de datos )
| Número de pieza | MAX1898 | |
| Descripción | Linear Charger for Single-Cell Li Battery | |
| Fabricantes | Maxim Integrated | |
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19-2295; Rev 0; 1/02
Linear Charger for Single-Cell Li+ Battery
General Description
The MAX1898, with an external PNP or PMOS transistor,
forms a complete charger for 1-cell lithium-ion (Li+) bat-
teries. The MAX1898 provides accurate constant-cur-
rent/constant-voltage charging. Battery regulation voltage
accuracy is ±0.75% for optimum battery performance
and cycle life. Charging current is user set, but is sensed
internally so no external current-sense resistor is needed.
The MAX1898 also provides outputs to monitor charge
status, presence-of-input power source, and charge cur-
rent. Additional features include shutdown, optional
charge-cycle restart without input-power cycling, selec-
table charge termination safety timer, and low-current
preconditioning for deeply discharged cells.
The MAX1898 offers the maximum integration and func-
tionality in the smallest, most basic application circuit
possible. Very few external components are required.
The MAX1898 offers two versions to safely charge all
Li+ battery chemistries. The battery regulation voltage
is 4.2V for the MAX1898EUB42 and 4.1V for the
MAX1898EUB41. Both are available in a 10-pin ultra-
thin µMAX package.
Applications
Single-Cell Li+ Powered Portables
Self-Charging Battery Packs
PDAs
Cell Phones
Cradle Chargers
TOP VIEW
IN 1
CHG 2
EN/OK 3
ISET 4
CT 5
Pin Configuration
MAX1898
µMAX
10 CS
9 DRV
8 GND
7 BATT
6 RSTRT
Features
o Simple, Safe Linear Charger
o Uses Low-Cost PNP or PMOS Pass Element
o 4.5V to 12V Input Range
o Internal Current-Sense Resistor
o ±0.75% Voltage Accuracy
o Programmable Charging Current
o Automatic Input Power-Source Detection
o LED Charge Status Indicator
o Programmable Safety Timer
o Current-Sense Monitor Output
o Optional/Adjustable Auto-Restart
o Small µMAX Package
PART
MAX1898EUB42
MAX1898EUB41
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
10 µMAX
Typical Operating Circuit
INPUT
4.5V TO 12V
LED
ON
OFF
CT SETS
CHARGE
TIME
IN CS
MAX1898
CHG DRV
EN/OK
CT
BATT
ISET
RSTRT
GND
SETS CHARGE
CURRENT
OUTPUT
Li+
BATTERY
________________________________________________________________ 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.
1 page  
Linear Charger for Single-Cell Li+ Battery
Typical Operating Characteristics
(VIN = 5V, VBATT = 4V, EN/OK = open, RSET = 2.8kΩ, RSTRT = GND, TA = +25°C, unless otherwise noted.)
NORMALIZED TIMER PERIOD
vs. TEMPERATURE
1.02
NORMALIZED TO +25°C
1.00
0.98
NORMALIZED BATT REGULATION
VOLTAGE vs. TEMPERATURE
1.002
NORMALIZED TO +25°C
1.001
1.000
PRECHARGE CURRENT
vs. INPUT VOLTAGE
60
ISET = 2.8kΩ
CHARGING CURRENT SET
FOR 500mA
55
0.96 0.999
50
0.94 0.998
0.92 0.997
45
0.90
-40
-15 10 35 60
TEMPERATURE (°C)
85
0.996
-40
NORMALIZED BATTERY CURRENT
vs. BATTERY VOLTAGE
1.2
-15 10 35 60
TEMPERATURE (°C)
60
40
85 5 6 7 8 9 10 11 12
VIN (V)
VOLTAGE-LOOP GAIN
MAX1898 toc05
200
1.0 40 150
0.8
PHASE
GAIN
20 100
0.6
0 50
0.4
0.2 -20 0
0
3.9 4.0 4.1 4.2 4.3
BATTERY VOLTAGE (V)
-40
0.01
0.1 1
10 100
FREQUENCY (kHz)
-50
1000
_______________________________________________________________________________________ 5
5 Page 
Linear Charger for Single-Cell Li+ Battery
Selecting External Components
The MAX1898 drives an external transistor to control
charging current. The most important specifications for the
pass transistor (MOSFET or bipolar) are current rating and
package power dissipation. Since the MAX1898 operates
as a linear charger, heat will dissipate in the external tran-
sistor. The worst-case power dissipation will be:
PDISS(MAX) = IFASTCHG (VIN - 2.5V)
The pass transistor and heatsinking (typically an expand-
ed PC board plane) must be rated for PDISS(MAX).
The pass device will most commonly be a P-channel
MOSFET. Its operating voltage must exceed the
expected input voltage, but MOSFET on-resistance is
important only in low-dropout designs where VIN is only
slightly higher than the battery regulation voltage. In
most charger designs, a fairly low-cost FET (around
100mΩ to 200mΩ RDS(ON)) performs more than ade-
quately. Lower resistance FETs perform well also, but
are not worth the added cost in this case.
A PNP bipolar transistor may also be used as a pass
device. DRV can sink up to 4mA, so reasonable high
current gain (hFE or Beta) is required to allow DRV to
drive the base of a bipolar pass transistor. For a 500mA
fast-charge current, an hFE of 125 is required. Although
their current gain is high, Darlington PNP transistors are
not recommended due to stability limitations.
If VIN is less than VBATT, the body diode inherent in the
external enhancement-mode FET allows current to flow
from the cell back to the source. To prevent this, add a
Schottky diode between the drain and BATT, as shown
in Figure 4.
Chip Information
TRANSISTOR COUNT: 1816
PROCESS: BiCMOS
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX1898.PDF ] | |
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