Texas Instruments INA1620EVM, Руководство пользователя, Страница: 8 / 24

THD+N Ratio (dB)
Fr
eque
ncy
(H
z)
-110
-105
-100
-95
-90
-85
-80
100 1k 10k
Left Channel
Right Channel
Test Setup and Results
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8 SBOU205 – March 2018
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INA1620EVM Audio Amplifier Evaluation Module
4.2 Input Connections
Signals for the left channel and right channel inputs are applied through connectors J3 and J1,
respectively. Connect wires to J1 and J3 to provide an input signal from an audio source such as an audio
analyzer or audio digital-to-analog converter (DAC). The positive input connects to the pin l, the
negative input to the pin labeled –, and the ground connection connects to the center pin, marked GND.
4.3 Output Connections
Output connections are provided through the use of the audio jack, J2, and two test points labelled Left
Out and Right Out. The audio jack provides a way to connect headphones or a resistive load to the output
of the INA1620. The test points provide a connection to measure the performance of the two channels
with an audio analyzer, distortion analyzer, or other test equipment.
4.4 Enable
Jumper J4 provides access to the EN pin on the INA1620. Placing a shunt across J4 disables the
INA1620 by grounding the EN pin. When the EN pin is grounded, a current flows through R3 to ground
that is larger than the shutdown current of the OPA1622. Removing the shunt across J5 enables the
INA1620 by pulling the EN pin up to the positive supply through resistor R3. Voltages up to the positive
supply can be applied to the EN pin. External sources can be applied to the enable pin by removing the
shunt and resistor R3 and connecting an external source to J4.
4.5 THD+N vs. Frequency
For all THD+N vs Frequency measurements, the input signal frequency was swept from 20 Hz to 20 kHz
and had an amplitude of 1 V
RMS
on the output of the INA1620 with the measurement bandwidth of the
Audio Precision set to 90 kHz. A small variation in the THD+N performance between amplifier channels is
normal. Figure 4 shows the THD+N vs Frequency for a 32- Ω load.
Figure 4. THD+N vs Frequency for a 32-
Ω
Load