MAX1501
Highly Integrated, Linear Battery Charger with
Thermal Regulation for Portable Applications
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Thermal-Regulation Selection
Set the regulated die temperature of the MAX1501 with
the TEMP three-level logic input. The MAX1501
reduces the charge current to limit the die temperature
to the value set by TEMP. The MAX1501 operates nor-
mally while the thermal loop is active. An active thermal
loop does not indicate a fault condition. TEMP allows
the MAX1501 to maximize the charge current while pro-
viding protection against excessive power dissipation.
Connect TEMP to GND to regulate the die temperature
at +95°C. Leave TEMP floating to regulate the die tem-
perature at +115°C. Connect TEMP to VL to regulate
the die temperature at +135°C.
Top-Off-Current Selection
Set the top-off-current threshold in the Li+ and
NiMH/NiCd charge modes with the FULLI three-level
logic input. The top-off-current threshold determines
when RLED turns off and GLED turns on, indicating the
charge status of the battery.
Connect FULLI to GND to set the top-off-current thresh-
old to 10% of the fast-charge current. Connect FULLI to
VL to set the top-off-current threshold to 20% of the
fast-charge current. Leave FULLI floating to set the top-
off-current threshold to 30% of the fast-charge current.
Charge-Timer Selection (MAX1501 Only)
Set the maximum charging time with the TMAX three-
level logic input. TMAX limits the duration of charging to
protect the battery from overcharging. Connect TMAX
to GND to set the maximum charging time to 3 hours.
Leave TMAX floating to set the maximum charging time
to 4.5 hours. Connect TMAX to VL to set the maximum
charging time to 6 hours.
Capacitor Selection
Connect a ceramic capacitor from BATT to GND for
proper stability. Use a 10µF X5R ceramic capacitor for
most applications.
Connect IN and INP together and bypass to GND with
a 1µF ceramic capacitor. Use a larger input bypass
capacitor for high input voltages or high charging cur-
rents to reduce supply noise.
Thermal Considerations
The MAX1501 is available in a thermally enhanced thin
QFN package with exposed paddle. Connect the
exposed paddle of the MAX1501 to a large copper
ground plane to provide a thermal contact between the
device and the circuit board. The exposed paddle
transfers heat away from the device, allowing the
MAX1501 to charge the battery with maximum current,
while minimizing the increase in die temperature.
Application Circuits
Figure 5 shows the MAX1501 as a stand-alone Li+ bat-
tery charger. The 2.8kΩ resistor connected to SETI sets
a charging current of 500mA.
Figure 6 shows the MAX1501 as a µP-based Li+ battery
charger. Drive CHGEN low to charge the battery. Drive
CHGEN high to disable the charger. Connect a 100kΩ
pullup resistor from ACOK to the logic supply voltage of
the µP to detect the presence of an input supply. The
logic supply voltage must be less than 5.5V.
TMAX/I.C.
TMAX/I.C.
