MAX1501 Datasheet, PDF (10/15 Pages) Maxim Integrated Products – Highly Integrated, Linear Battery Charger with Thermal Regulation for Portable Applications

Highly Integrated, Linear Battery Charger with
Thermal Regulation for Portable Applications
Table 2. Battery Regulation Voltage
CHARGING MODE
Li+
NiMH/NiCd
GND
4.1V
4.5V
SELV
VL
4.2V
4.95V
Li+ Charge Mode
Connect CHGEN and MODE to GND to place the
MAX1501 in Li+ charging mode. The Li+ charger con-
sists of a voltage-control loop, a current-control loop,
and a thermal-control loop. Connect SELV to GND to
set the Li+ battery voltage to 4.1V. Connect SELV to VL
to set the Li+ battery voltage to 4.2V (Table 2).
The MAX1501 precharges the Li+ battery with 10% of
the user-programmed fast-charge current at the start of
a charge cycle. A soft-start algorithm ramps up the
charging current (10% steps with 20ms duration per
step) to the fast-charge current when the battery volt-
age reaches 2.8V. The MAX1501 enters constant-volt-
age mode and decreases the charge current when the
BATT voltage reaches the selected regulation voltage
(4.1V or 4.2V). Set the fast-charge current with a resis-
tor between SETI and GND (see the Charge-Current
Selection section).
The thermal-regulation loop limits the MAX1501 die
temperature to the value selected by the TEMP input by
reducing the charge current as necessary (see the
Thermal-Regulation Selection section). This feature not
only protects the MAX1501 from overheating, but also
allows the charge current to be set higher without
risking damage to the system.
Set the top-off-current threshold with the three-state
FULLI input (see the Top-Off-Current Selection section).
RLED goes high impedance and GLED asserts low when
the top-off-current threshold is reached. The MAX1501
automatically initiates recharging when the battery volt-
age drops below 95% of the voltage set by SELV.
NiMH/NiCd Charge Mode
Connect CHGEN to GND and MODE to VL to place the
MAX1501 in NiMH/NiCd charging mode. The
NiMH/NiCd battery charger consists of a current-con-
trol loop, a voltage-control loop, and a thermal-control
loop. Connect SELV to GND to set the regulation volt-
age to 4.5V. Connect SELV to VL to set the regulation
voltage to 4.95V (Table 2). When charging three
NiMH/NiCd cells to 4.95V, V_IN must be at least 5.25V
and a µP must be used to terminate the charge
sequence.
REGULATION VOLTAGE ^{PREQUALIFICATION}
FAST-CHARGE CURRENT
FAST CHARGING
MINIMUM CHARGE VOLTAGE
(2.8V)
10% OF FAST-CHARGE CURRENT
t_PREQUAL
BATTERY
VOLTAGE
t_MAX
TOP-OFF
DONE
BATTERY
CURRENT
RLED TURNS OFF AND GLED
TURNS ON WHEN CHARGE CURRENT
DROPS TO VALUE SET BY FULLI
(10%, 20%, OR 30% OF FAST-
CHARGE CURRENT).
CHARGE
TERMINATED
Figure 3. Li+ Charge Sequence
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