DS2731K Maxim Integrated, DS2731K Datasheet - Page 4

• Manufacturer Part Number: DS2731K
• Description: Power Management IC Development Tools
• Manufacturer: Maxim Integrated
• Series: DS2731r

power is cycled or the ENC pin is strobed low and then
returns high. The timer does not start until CC mode is
entered and continues through CV mode; precharge
mode is not included in the STMR.
The buck regulator output voltage can range from
+0.9V to +2.5V and is set by the following formula:
The board is shipped with V
The supply powering the buck regulator is the auxiliary
supply as long as it is > 2.93V. If the voltage of the aux-
iliary supply drops below 2.93V, the DS2731 automati-
cally switches power to the Li+ battery.
The IC transitions to a quiescent-power mode should
the Li+ battery reach empty before the system power is
restored. In this mode, all circuitry is shut off and does
not turn on again until the V
UVLO-REG is off. The low-battery voltage set point can
be determined by the following formula:
The board is shipped with the low-battery voltage set
point = +2.76V.
DS2731 Evaluation Kit
4
_______________________________________________________________________________________
V
LO_BATT
x 4.5 = low-battery voltage set point
V
DIV
x 25/12 = V
REG
CBIAS
Low-Battery Shutdown
= +1.8V.
VREG
voltage is stable and
Regulation Voltage
Buck Regulator
The features of the charge circuitry can be easily
demonstrated when a source/sink supply is connected
between BAT+ and BAT-. With the +12V and +3.3V
supplies connected and on, lower the source/sink sup-
ply’s voltage below +4.0V (make sure the current limit
of the supply is set above the charge current I
The yellow LED should turn on. If the source/sink sup-
ply has a current meter display, it should read approxi-
mately equal to I
voltage below V
charge current. Increase the source/sink supply volt-
age above V
observe the green LED turn on.
Heat the IC up to > +160°C. Above +100°C, the IC
begins to choke the charge current 133mA/°C. Once
the die temperature exceeds +160°C, the charge cur-
rent shuts off completely.
With the +12V and +3.3V supplies and the Li+ battery
connected, the voltage reading between MEM+ and
MEM- should be approximately +1.8V. If a programma-
ble load is being used, set the load current to 150mA.
The user should be able to observe the current being
drawn from the +3.3V auxiliary supply. Power down the
+12V and +3.3V supplies and observe that the buck
regulator is still running. Power up the +12V and +3.3V
supplies again and operation of the buck regulator
should remain constant during the switchovers.
PK
, the constant voltage set point, and
CHARGE
MIN
and there is a reduction in the
. Lower the source/sink supply
Board Operation
Buck Regulator
Charger
CHARGE
).