5 Connection Descriptions

PCB Silkscreen	Description
VIN	VIN is the input voltage terminal to the PCB and is equipped to handle a ¼-inch banana jack or can be unbolted to accept a ring connector. The LM27402 will operate over the input voltage range of 3.0 V to 20 V. However, the evaluation board is optimized for an input voltage of 12 V and will operate from 4.5 V to 12 V. The absolute maximum voltage rating for this pin is 22 V.
GND IN	GND IN is the input ground terminal to the PCB and is equipped to handle a ¼-inch banana jack or can be unbolted to accept a ring connector. There are two GND connections on the PCB. GND IN should be used for the input supply only.
VOUT	VOUT is the output voltage terminal of the PCB and is equipped to handle a ¼-inch banana jack or can be unbolted to accept a ring connector. VOUT should be connected to the load through a low impedance line to minimize any line drop.
GND OUT	GND OUT is the output ground terminal of the PCB and is equipped to handle a ¼-inch banana jack or can be unbolted to accept a ring connector. There are two GND connections on the PCB. GND OUT should be used for the output load only.
VDD	VDD is the output of the internal 4.5-V sub regulator.
PGD	PGOOD output. This connection allows the user to monitor PGOOD during fault conditions. PGOOD is pulled up to VDD and should not exceed 5.5 V under normal operating conditions and the absolute maximum voltage rating is 6 V.
EN	EN is connected to the EN pin of the LM27402. A voltage typically greater than 1.17 V will enable the IC. A hysteresis of 100 mV on EN provides noise immunity. The LM27402 will self enable by a 2-µA internal current source to EN if no control signal is applied to EN. The enable threshold can be set with an optional external resistor divider from VIN. The EN pin should not exceed the voltage on VDD. The operating voltage for this pin should not exceed 5.5 V and the absolute maximum voltage rating is 6 V.
SS/TK	SS/TK provides access to the SS/TRACK pin of the LM27402. Connections to this terminal are not needed for most applications. The feedback pin of the LM27402 will track the voltage on the SS/TRACK pin if driven with an external voltage source that is less than the 0.6-V internal reference. The operating voltage for this pin should not exceed 5.5 V and the absolute maximum voltage rating on this pin is 6 V. The SS/TRACK pin should not exceed the voltage on VDD.
SYNC	SYNC connects to the SYNC pin of the LM27402. An external clock signal can be connected to the SYNC connection to set the switching frequency. If a SYNC signal is not present, the switching frequency will fall back to the frequency set by the FADJ resistor. The SYNC frequency must be greater than the frequency set by the FADJ resistor and can sync up to 400 kHz above the free running frequency. This pin should not exceed the voltage on VDD.
RX and TX	The RX and TX terminals provide the connections to measure the loop response with a network analyzer. RX refers to an applied reference signal and TX refers to the test voltage or in this case the output voltage. Between RX and TX exists a 50-Ω termination resistor.