MAX846AEEE Maxim Integrated Products, MAX846AEEE Datasheet - Page 10

• Manufacturer Part Number: MAX846AEEE
• Description: Battery Management Multichemistry Bat Charger System
• Manufacturer: Maxim Integrated Products

Specifications of MAX846AEEE

• Battery Type: Li-Ion, Li-Polymer, NiCd, NiMH
• Output Voltage: 3.3 V
• Operating Supply Voltage: 3.7 V to 20 V
• Supply Current: 5 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: QSOP-16
• Mounting Style: SMD/SMT

Cost-Saving Multichemistry
Battery-Charger System
Figure 3. Desktop Multichemistry Charger Concept
Component selection is similar to that of stand-alone
operation. By using DACs or µC PWM outputs, the float
voltage and charging current can be adjusted by the
µC. When a Ni-based battery is being charged, disable
the float-voltage regulation using the OFFV input. The
µC can also monitor the charge current through the
battery by reading the ISET output’s voltage using its
ADC. Similarly, the battery voltage can be measured
using a voltage divider from the battery.
Note that the µC only needs to configure the system for
correct voltage and current levels for the battery being
charged, and for Ni-based batteries to detect end-of-
charge and adjust the current level to trickle. The con-
troller is not burdened with the regulation task.
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DCIN
3.7V TO 20V
CCI
CCV
GND
PGND
DCIN
CS+
CS-
MAX846A
DRV
P
PWROK
CELL2
BATT
OFFV
VSET
ISET
ON
VL
Float-voltage accuracy is important for battery life and
for reaching full capacity for Li-Ion batteries. Table 1
shows the accuracy attainable using the MAX846A.
For best float-voltage accuracy, set the DRV current to
1mA (R
The circuit in Figure 6 minimizes power dissipation in
the pass transistor by providing optical feedback to the
input power source. The offline AC/DC converter main-
tains 1.2V across the PNP. This allows much higher
charging currents than can be used with conventional
power sources.
DRV
= 660Ω for a PNP pass transistor).
Li OR Ni
High-Power Multichemistry
RST
ADC (MEASURE V(BATT))
I/O (LOW = TURN OFF CHARGE)
I/O (HIGH = 2 Li CELLS)
I/O (HIGH = DISABLE FLOAT V)
PWM/DAC (CONTROL FLOAT V)
PWM/DAC (CONTROL CHARGE I)
ADC (MEASURE I
V
DD
MICROCONTROLLER
Offline Charger
BATT
)