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100% Duty Cycle Low Dropout Operation
V
I(min) +
V
O(max) )
I
O(max)
r
DS(on) max )
R
L
(2)
Active Discharge When Disabled
Power-Good Monitoring
Overtemperature Shutdown
LOW-DROPOUT VOLTAGE REGULATORS
Power-Good Monitoring
Enabling and Sequencing
TPS65014
SLVS551 – DECEMBER 2004
The TPS65014 converters offer a low input to output voltage difference while maintaining operation with the use
of the 100% duty cycle mode. In this mode, the P-channel switch is constantly turned on. This is particularly
useful in battery-powered applications to achieve longest operation time by taking full advantage of the whole
battery voltage range. The minimum input voltage to maintain regulation depends on the load current and output
voltage and is calculated as:
with:
IO(max) = maximum output current plus inductor ripple current
rDS(on)max= maximum P-channel switch rDSon.
RL = DC resistance of the inductor
VO(max)= nominal output voltage plus maximum output voltage tolerance
When the CORE and MAIN converters are disabled, due to an UVLO, BATT_COVER or OVERTEMP condition,
it is possible to actively pull down the outputs. This feature is disabled per default and is individually enabled via
the VDCDC1 and VDCDC2 registers in the serial interface. When this feature is enabled, the core and main
outputs are discharged by a 400-
(typical) load.
Both the MAIN and CORE converters have power-good comparators. Each comparator indicates when the
relevant output voltage has dropped 10% below its target value, with 5% hysteresis. The outputs of these
comparators are available in the REGSTATUS register via the serial interface. A maskable interrupt is generated
when any voltage rail drops below the 10% threshold. The comparators are disabled when the converters are
disabled. The status of the power-good comparator for VMAIN is used to generate the RESPWRON signal.
The MAIN and CORE converters are automatically shut down if the temperature exceeds the trip point (see the
electrical characteristics). This detection is only active if the converters are in PWM mode, either by setting
FPWM = 1, or if the output current is high enough that the device runs in PWM mode automatically.
The low-dropout voltage regulators are designed to operate with low value ceramic input and output capacitors.
They operate with input voltages down to 1.8 V. The LDOs offer a maximum dropout voltage of 300 mV at rated
output current. Each LDO has a current limit feature. Both LDOs are enabled per default; both LDOs can be
disabled or programmed via the serial interface using the VREGS1 register. The LDO outputs (when enabled)
are monitored by power-good comparators, the outputs of which are available via the serial interface. The LDOs
also have reverse conduction prevention when disabled. This allows the possibility to connect external regulators
in parallel in systems with a backup battery.
Both the LDO1 and LDO2 linear regulators have power-good comparators. Each comparator indicates when the
relevant output voltage has dropped 10% below its target value, with 5% hysteresis. The outputs of these
comparators are available in the REGSTATUS register via the serial interface. An interrupt is generated when
any voltage rail drops below the 10% threshold. The LDO2 comparator is disabled when LDO2 is disabled.
Enabling and sequencing of the dc-dc converters and LDOs are described in the power-up sequencing section.
The OMAP1510 processor from Texas Instruments requires that the core power supply is enabled before the I/O
power supply, which means that the CORE converter should power up before the MAIN converter. This is
achieved by connecting PS_SEQ to GND.
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