MAX1898EUB41-T Maxim Integrated Products, MAX1898EUB41-T Datasheet - Page 11

• Manufacturer Part Number: MAX1898EUB41-T
• Description: Battery Management Linear Charger for 1-Cell Li+ Battery
• Manufacturer: Maxim Integrated Products

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:
The pass transistor and heatsinking (typically an expand-
ed PC board plane) must be rated for P
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 V
slightly higher than the battery regulation voltage. In
most charger designs, a fairly low-cost FET (around
100mΩ to 200mΩ R
quately. Lower resistance FETs perform well also, but
are not worth the added cost in this case.
P
DISS(MAX)
Selecting External Components
Linear Charger for Single-Cell Li+ Battery
______________________________________________________________________________________
DS(ON)
= I
FASTCHG
) performs more than ade-
(V
IN
DISS(MAX)
- 2.5V)
IN
.
is only
A PNP bipolar transistor may also be used as a pass
device. DRV can sink up to 4mA, so reasonable high
current gain (h
drive the base of a bipolar pass transistor. For a 500mA
fast-charge current, an h
their current gain is high, Darlington PNP transistors are
not recommended due to stability limitations.
If V
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.
TRANSISTOR COUNT: 1816
PROCESS: BiCMOS
IN
is less than V
FE
or Beta) is required to allow DRV to
BATT
, the body diode inherent in the
FE
of 125 is required. Although
Chip Information
11