MAX846AEEE View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX846AEEE Datasheet PDF : 12 Pages
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Cost-Saving Multichemistry
Battery-Charger System
DCIN
3.7V TO 20V
100k
0.01µF
0.01µF
4.7µF
( ) 0.165V
IBATT
EXTERNAL PASS TRANSISTOR
CAN BE EITHER PNP OR PMOS FET.
RCS 10nF
RDRV
660Ω
CS+
CS-
DRV
DCIN
VL
MAX846A
4.7µF
BATT
VSET
RVSET
VL
ADJUST
(UP)
(DOWN)
PWROK
ON
CCI
CCV
OFFV
GND
10k
ISET
RISET
PGND
CELL2
VL
(2 CELLS)
(1 CELL)
Figure 2. Stand-Alone Li-Ion Charger
RVSET = 20kΩ
4.2
1.65
VX
−
VF
VF − 4.2
where VX is either GND or VL, and VF is the per-cell
float voltage. In the circuit of Figure 1, RVSET is
400kΩ. RVSET and the internal 20kΩ resistor form a
divider, resulting in an adjustment range of approxi-
mately ±5%.
The current-regulation loop attempts to maintain the
voltage on ISET at 1.65V. Selecting resistor RISET deter-
mines the reflected voltage required at the current-
sense amplifier input.
• Calculate RCS and RISET as follows:
RCS = VCS / IBATT
RISET (in kΩ) = 1.65V / VCS
where the recommended value for VCS is 165mV.
• Connect ON to PWROK to prevent the charge current
from turning on until the voltages have settled.
Minimize power dissipation in the external pass transis-
tor. Power dissipation can be controlled by setting the
DCIN input supply as low as possible, or by making
VDCIN track the battery voltage.
Microprocessor-Controlled
Multichemistry Operation
The MAX846A is highly adjustable, allowing for simple
interfacing with a low-cost µC to charge Ni-based and
Li-Ion batteries using one application circuit (Figure 3).
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