MAS6011B datasheet(2/10 Pages) MAS

2 / 10 page

DA6011B.001

18 October, 2011

2 (10)

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.

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

extremely

low.

The

electrical

parameters are described more detailed in the

Electrical Characteristics chapter.

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.

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.

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.

SOL is used for controlling the charging of the

rechargeable battery. Normally the internal PMOS

switch between VDD and the SOL pin is non-

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).

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.

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

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.

Figure 1 illustrates the MAS6011 functions and

shows the comparator switching levels for both

battery charging (rising VDD) and discharging

(falling VDD) conditions.

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