DA9128A.002

July 12, 1998

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The device is supplied with 3.1V to 6.5V battery

voltage under normal conditions. An internal band

gap voltage reference is used to generate the

reference voltage for all three voltage regulators.

The reference voltage is routed via an internal

20kOhm Resistor to an external pin where a filter

capacitor can be connected in order to reduce the

noise level of all three regulators. The startup time

of the reference voltage is then determined by the

value of the bypass capacitor at pin VREF.

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Each regulator can be enabled/disabled by the two

enable pins ENA and ENBC. Pin ENA controls

regulator LDO_A and pin ENBC controls both

regulators LDO_B and LDO_C. If both enable pins

are forced low, the internal voltage reference and

internal bias source are turned off in order to save

power. A common enable for all three regulator

outputs

is

designed,

but

connected

to

VDD

internally for the SOIC8 version of MAS9128A.

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The device contains three 2.85V low dropout

CMOS regulators with maximum output currents of

100mA, 70mA and 50mA. There is a mask option

to modify the output voltage to 2.55V, 2.70V,

2.85V, 3.00V or 3.15V. The IC has thermal

protection in order to prevent thermal destruction

especially at high ambient temperatures. Maximum

output current of each regulator is limited by an

internal

circuitry.

The regulation loop of

the

regulators is optimized to work with low ESR

ceramic buffer capacitors at the output.

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