DA6011.000
15 September 2008
FUNCTIONAL DESCRIPTION
The solar manager generates three signals: XPD
(Power Down), LB (Low Battery) and SOL (Solar
Charging).
These signals are produced by three comparators
which have hysteresis build in. Each comparator
compares supply voltage (VDD) to internal switching
levels (see Electrical Characteristics on the next
page). The current consumption of the comparators
is extremely low. The electrical parameters are
described more detailed in the Electrical
Characteristics chapter.
XPD signal can be used to stop the whole system
whenever the power supply level has dropped low
enough. When the power supply voltage is too low
the XPD goes low to signal the microcontroller to go
to power down. When the power supply voltage is
high enough the XPD goes high signaling power up
situation.
In case of low power microcontroller (max current
consumption about 150
µA)
the XPD pin can be
used to feed supply voltage directly to the
microcontroller by connecting XPD pin to the supply
voltage pin of the microcontroller (see application
figure 3).
LB signal indicates that the battery is low but not
empty. LB goes high when power supply level is too
VDD
3.3V
3.2V
3.1V
3.0V
2.9V
2.8V
BATTERY CHARGING
(VDD RISING)
BATTERY DISCHARGING
(VDD FALLING)
SOL_OFF (charging off)
SOL_ON (charging on)
low and LB goes low when power supply level is
high enough.
SOL is used for controlling the charging of the
rechargeable battery. When power supply voltage
goes high enough, the internal PMOS switch
between VDD and SOL pins is switched on to shunt
the solar cell charging current and to prevent battery
overcharging. When the power supply voltage is not
too high the internal PMOS switch is non-
conductive.
In operation without an external Schottky diode
between the pins SOL and GND, the voltage at pin
SOL is clamped to about 700 mV below GND by an
internal diode-connected PNP transistor.
MAS6011 does not have any control pin. After the
power supply is connected the device is ready to be
used.
Figure 1 illustrates MAS6011 functions and shows
the comparator switching levels at both battery
charging (rising VDD) and discharging (falling VDD)
conditions. The XPD, LB and SOL switching levels
have been designed for usage of VL-type
rechargeable lithium batteries.
Battery Voltage
LB_OFF (low battery off)
XPD_OFF (power down off)
2.7V
2.6V
2.5V
2.4V
2.3V
2.2V
2.1V
2.0V
LB_ON
(low battery on)
XPD_ON
(power down on)
Figure 1.
MAS6011 functions
3 (8)
MAS [ MICRO ANALOG SYSTEMS ]
