LX1790 E
VALUATION
B
OARD
U
SER
G
UIDE
Copyright © 2002
Microsemi
Page 5
Rev 0.2, 3/4/2002
Integrated Products – Power Management
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Q
UICK
S
TART
G
UIDE
The LX1790 Evaluation Board is a fully functional,
Class-D Amplifier. To begin evaluation of the
LX1790, just follow these simple steps.
1) Visually inspect the board to make sure that
components were not damaged during
shipping.
2) Power and Ground Connections The power
and ground connections are made through
banana jacks J3 and J4. Connect the positive
terminal of the power supply or battery to J3,
which is labeled "VDD". Connect the
negative terminal of the supply or battery to
J4, which is labeled "VSS". Make sure the
correct connections are made before turning
on power supply.
3) Input
Connection
To input a function generator signal, connect
source to jack J1, labeled "BNC IN". To
input an audio signal, connect source to jack
J2, labeled "RCA IN".
4) Input
Selection
If using the BNC jack, set Input Select switch
SW1 to the "BNC" position. If using the
RCA jack, set SW1 to the "RCA" position.
5) Gain
Selection
Choose between three gain settings of 14dB,
20dB, and 26dB. Set the Gain Select switch
SW3 to the desired gain setting.
6) Output Impedance Selection
For most Evaluation Board applications, the
Impedance Select switch SW2 should be set
to 10
Ω
. The other impedance settings reduce
current consumption with the tradeoff of
increasing switch output impedance.
7) Output
Select
The "Headphone" setting will directly
connect the differential output of the
amplifier to the headphone jack. The
"Single-Ended" setting will connect the
differential amplifier output to a transformer
and convert it to a single-ended signal. The
single-ended signal is then low-pass filtered
with a cutoff frequency of 20kHz. The
output of the low-pass filter is connected to
BNC jack J5. The "Unloaded" setting will
disconnect the amplifier from either load.
8) Output
Connection
To listen to the output of the amplifier,
connect headphones to J7, labeled
"Headphone OUT", and verify that the
Output Select is set to "Headphone".
Headphones with a minimum impedance of
150
Ω
should be used. To view the amplifier
output on either a spectrum analyzer or an
oscilloscope, connect to BNC connector J5,
labeled "Single-Ended OUT", and verify
SW4 is set to "Single-Ended".
9) Breadboard
The differential output signal is directly
available on the breadboard. The positive
output is labeled "OUTP", and the negative
output is labeled "OUTN". The power
supply ground is also available on the
breadboard, and is labeled "GND". BNC
connector J6 is provided to access the
breadboard output, which is labeled
"BREADBOARD OUT". The positive
output pin of J6 is wired to the breadboard,
and is labeled "BB OUT". When using the
breadboard, make sure the Output Select
switch is set to "Unloaded".
10) Power Source
If using a power supply, verify that it is set to
1.25V before connecting it to the Evaluation
Board. A "C" (1.5V) battery can also be
used.
11) Signal Generator Source
Set the signal generator to the appropriate
level for best results (see table below).
Vin
Gain Setting
100mVrms 14dB
50mVrms 20dB
25mVrms 26dB
