Just want to make sure is the C11 (FIGURE on EV board datasheet). of LMH6515 evaluation board shorted on the PC board ?I check with multimeters, and it shows C11 is shorted, but not shorted in the datasheet.
Thank you !
Hello Jerry,
C11 should NOT be shorted. Otherwise the transformer will short the power supply, and, if supply current is not limited, damage the transformer or L1/L2 bias inductors.
C11 may measure as a short in-circuit because of the parallel path through the transformer and through the L1/L2 1uH bias inductors back through the part power supply pins to ground. You would have to remove C11 to see if it is truly shorted..
Paul Grohe
Integrated Signal Chain Applications, SVA
Paul is correct. Most likely you are measuring current flowing through other circuit elements.
You may want to try swapping the test leads on your multimeter. There is a Shottkey protection diode across the power pins that protects the amplifier from reverse polarity power supplies. Your DVM may be measuring this diode, or it may be measuring current that is flowning into the amplifier.
If you apply 5V to the power connnections what supply current do you read? Is there any performance problem that leads you to suspect a short?
C11 is not supposed to be installed when the board is shipped and it is not necessary. With 5V applied to the power connectors there should be 5V reading at pins 1, 2 and 3 of T2. If there is 5V at these pins and there is not excessive supply current then there is no short circuit.