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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