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The MAX8672 complete power manager for backup
batteries in smart devices offers feature-programmable
battery charging and main-system backup. The device
includes a charger for 1- or 2-cell NiMH backup batteries.
A low-quiescent current synchronous-rectified
boost converter and LDO supply up to 20mA during
system backup conditions. The BST output is internally
set to regulate at 3.05V. The MAX8672 LDO is powered
from the boost converter output and is adjustable from
1.5V to 3.05V.
The MAX8672 features programmable charge current,
undervoltage lockout (UVLO), and maximum cell voltage.
Charging is controlled by both a timer and thermistor
monitor. Battery UVLO prevents excessive
battery discharge and keeps inactive-battery drain current
below 50nA. In addition, both LDO and boost converter
outputs block reverse current so that diodes are
not needed when connecting these outputs directly to
system supplies. The MAX8672 requires that a valid
system supply be present before system backup operation
can occur.
Charging is managed by a current source that charges
until the battery reaches the programmed voltage limit,
or the charge timer expires.
The MAX8672 is available in a 14-pin, 3mm x 3mm TDFN
package and is rated for -40°C to +85°C operation.
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