TPS2505

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SPAS093A – DECEMBER 2009 – REVISED FEBRUARY 2010

PGND

PGND is the internal ground connection for the source of the low-side N-channel MOSFET in the boost

converter. Connect PGND to an external plane near the ground connection of the input and output capacitors to

minimize parasitic effects due to high switching currents of the boost converter. Connect PGND to GND and the

thermal pad externally at a single location to provide a star-point ground. See LAYOUT RECOMMENDATIONS

for further details.

IN

IN is the input voltage supply for the boost converter. Connect a 10-µF ceramic capacitor (minimum) from IN to

PGND. See COMPONENT RECOMMENDATIONS for further details on selecting the input capacitor.

EN

EN is a logic-level input that enables the boost converter. Pull EN above 1 V to enable the device and below

0.7 V to disable the device. EN also disables the USB switches and LDO.

GND

Signal and logic circuits of the TPS2505 are referenced to GND. Connect GND to a quiet ground plane near the

device. An optional 0.1-µF capacitor can be connected from VIN to GND close the device to provide local

decoupling. Connect GND and PGND to the thermal pad externally at a single location to provide a star-point

ground. See LAYOUT RECOMMENDATIONS for further details.

ILIM1/2

Connect a resistor from ILIM1/2 to GND to program the current-limit threshold of the USB switches. Place this

resistor as close to the device as possible to prevent noise from coupling into the internal circuitry. Do not drive

ILIM1/2 with an external source. The current-limit threshold is proportional to the current through the RILIM

resistor. See Programming the Current-Limit Threshold Resistor RILIM for details on selecting the current-limit

resistor.

RESET

The RESET output indicates when the LDO output reaches 3.1 V. It has a 175-ms delay for deglitch in the low to

high transition. The output has in internal 10-k

Ω pull-up resistor to the LDO output.

LDOOUT

LDOOUT is the LDO output. Internal feedback regulates LDOOUT to 3.3 V. Connect a 1-µF ceramic capacitor

from LDOOUT to PGND for compensation. See COMPONENT RECOMMENDATIONS for further details.

LDOIN

LDOIN is the input voltage supply for the LDO. Connect a 4.7-µF ceramic capacitor from LDOIN to PGND when

not powered by AUX. See COMPONENT RECOMMENDATIONS for further details on selecting the input

capacitor.

ENLDO

ENLDO is a logic-level input that enables the 3.3-V LDO. Pull EN above 1 V to enable the device and below

0.7 V to disable the device. The boost converter must be enabled in order for the LDO to be enabled. The boost

converter is independent of ENLDO and continues to operate even when ENLDO disables the LDO.

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