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Connection Descriptions

5 Connection Descriptions

PCB Silkscreen Description

VIN VIN is the input voltage terminal to the PCB and is equipped to handle a 1/4" banana jack or

can be unbolted to accept a ring connector. The LM27402 will operate over the input voltage

range of 3.0V to 20V. However, the evaluation board is optimized for an input voltage of 12V

and will operate from 4.5V to 12V. The absolute maximum voltage rating for this pin is 22V.

GND IN GND IN is the input ground terminal to the PCB and is equipped to handle a 1/4" 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 1/4" 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 1/4" 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 4.5V 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 5.5V under normal operating conditions

and the absolute maximum voltage rating is 6V.

EN EN is connected to the EN pin of the LM27402. A voltage typically greater than 1.17V will

enable the IC. A hysteresis of 100mV 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 5.5V and the

absolute maximum voltage rating is 6V.

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 0.6V internal

reference. The operating voltage for this pin should not exceed 5.5V and the absolute

maximum voltage rating on this pin is 6V. 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 50Ω termination resistor.

SNVA406B–May 2010–Revised May 2013 AN-1992 LM27402 Evaluation Board

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