Texas Instruments LMH6515 Digital Controlled Variable Gain Amplifier Evaluation Board LMH6515EVAL/NOPB LMH6515EVAL/NOPB Datenbogen
Produktcode
LMH6515EVAL/NOPB
Basic Operation
For differential output signals remove transformer T2. Capacitor C11 can be left empty. Do not install
resistor R4. Using the transformer T2 pads, place coupling capacitors between pads 3 and 4 and between
pads 1 and 6 where the transformer would have been. These should be low ESR ceramic capacitors with
a value of 1nF. These output coupling capacitors are necessary to isolate the output common mode
voltage of the LMH6515 from the test equipment. The pads for capacitors C13 and C14 can be used as
series output matching resistors. There is no copper between transformer pad #6 and C14. A low
impedance short will have to be added manually. Resistors R3 and R4 are normally left empty in this
configuration.
resistor R4. Using the transformer T2 pads, place coupling capacitors between pads 3 and 4 and between
pads 1 and 6 where the transformer would have been. These should be low ESR ceramic capacitors with
a value of 1nF. These output coupling capacitors are necessary to isolate the output common mode
voltage of the LMH6515 from the test equipment. The pads for capacitors C13 and C14 can be used as
series output matching resistors. There is no copper between transformer pad #6 and C14. A low
impedance short will have to be added manually. Resistors R3 and R4 are normally left empty in this
configuration.
The evaluation board supports two gain options. As shipped the evaluation board provides for a low gain,
200
200
Ω
output impedance configuration. In order to use the high gain 400
Ω
configuration, the traces from
pins 13 and 16 to VCCA can be cut. For a detail of the trace cuts required, see
SW1 is used to set the five gain control bits. When the latch position of SW1 is in 0 or OFF position,
changes in the gain 0 to gain 5 bits are processed by the LMH6515. When the latch switch is in 1 or ON
position, the last loaded state is held and gain bit switch changes have no affect. Landings for SMA
connectors are also provided for high speed triggering of the gain bits.
changes in the gain 0 to gain 5 bits are processed by the LMH6515. When the latch switch is in 1 or ON
position, the last loaded state is held and gain bit switch changes have no affect. Landings for SMA
connectors are also provided for high speed triggering of the gain bits.
The LMH6515EL evaluation board is a four layer board; all four layers are detailed in
through
2
AN-1580 LMH6515EL Digital Controlled, Variable Gain Amplifier Evaluation
SNOA482B – September 2007 – Revised May 2013
Board
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