DA6011B.001
18 October, 2011
FUNCTIONAL DESCRIPTION
The solar manager generates three main signals:
XPD (Power Down), LB (Low Battery) and SOL
(Solar Charging). The fourth SW signal is for
controlling an optional external PMOS transistor.
conductive but when the power supply voltage rises
too much this switch is switched on to shunt the
solar cell charging current and to prevent battery
overcharging. The maximum shunt current
capability of the internal PMOS switch is typically
28 mA. If a larger shunt current is needed an
external PMOS transistor can be used controlled by
the SW pin (see application figure 6).
These signals are produced by three comparators
which have hysteresis build in. Each comparator
compares the supply voltage (VDD) to the internal
switching levels. The current consumption of the
comparators is extremely low. The electrical
parameters are described more detailed in the
Electrical Characteristics chapter.
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 NPN transistor.
The XPD signal can be used to power down the
whole system whenever the supply voltage level
has dropped too low (see application figure 4).
When the supply voltage is too low the XPD goes
low to power down the solar powered system.
When the supply voltage is high enough the XPD
goes high controlling power up condition.
MAS6011 does not have any control pin. After the
power supply is connected the device is ready to be
used.
The XPD, LB and SOL/SW switching levels have
been designed for usage with VL-type rechargeable
For a low power system (max current consumption
1mA) the XPD pin output can be used as a system
supply voltage (see application figure 5) to keep the
systems current consumption to a minimum.
lithium vanadium pentoxide batteries.
Those
batteries are compact, high energy secondary
batteries that have nearly twice the energy of
conventional button-shaped Ni-Cd batteries. The
self discharge rate is less than 2% a year which
makes them very useful as a power source in
systems that might be stored for a long time without
re-charging.
The LB signal indicates that the battery is low but
not empty. It can be used to control the system into
a power saving mode. In power on (XPD=high) LB
goes high when supply voltage level is too low and
LB goes low when supply voltage level is high
enough. In power down (XPD=low) the LB is low.
Figure 1 illustrates the MAS6011 functions and
shows the comparator switching levels for both
battery charging (rising VDD) and discharging
(falling VDD) conditions.
SOL is used for controlling the charging of the
rechargeable battery. Normally the internal PMOS
switch between VDD and the SOL pin is non-
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MAS [ MICRO ANALOG SYSTEMS ]
