Texas Instruments SoundPlus INA1651EVM User manual

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INA1651EVM SoundPlus™ High Common-Mode Rejection Line Receiver
Evaluation Module
User's Guide
SBOU212–September 2018
INA1651EVM SoundPlus™ High Common-Mode Rejection
Line Receiver Evaluation Module
This user's guide contains information for the INA1651 as well as support documentation for the INA1651
evaluation module (EVM). Included are the performance specifications, set-up procedure, modifications,
measured data, printed circuit board (PCB) layout, schematic, and bill of materials of the INA1651EVM.
Figure 1. INA1651 SoundPlus™ Evaluation Module (EVM)

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INA1651EVM SoundPlus™ High Common-Mode Rejection Line Receiver
Evaluation Module
Contents
1 Introduction ................................................................................................................... 3
2 EVM Measured Performance Summary.................................................................................. 3
3 Modifications.................................................................................................................. 3
3.1 AC-Coupled Corner Frequency................................................................................... 4
3.2 Filtering the VMID (IN) Pin......................................................................................... 4
3.3 Start-Up Time ....................................................................................................... 5
3.4 Increasing the Common-Mode Input Impedance............................................................... 5
4 Test Setup and Results..................................................................................................... 6
4.1 Power Supply Connections........................................................................................ 6
4.2 Input Connections .................................................................................................. 6
4.3 Output Connections ................................................................................................ 6
4.4 REF A and COM A ................................................................................................. 7
4.5 Common-Mode Rejection Ratio................................................................................... 9
4.6 THD+N vs. Amplitude .............................................................................................. 9
4.7 THD+N vs. Frequency............................................................................................ 10
4.8 Fast-Fourier Transform (FFT) ................................................................................... 11
5 Board Layout................................................................................................................ 12
5.1 Layout............................................................................................................... 12
6 Schematic, Bill of Materials, and Reference............................................................................ 14
6.1 Schematic .......................................................................................................... 14
6.2 Bill of Materials .................................................................................................... 15
6.3 Reference .......................................................................................................... 15
List of Figures
1 INA1651 SoundPlus™ Evaluation Module (EVM)....................................................................... 1
2 Simplified INA1651EVM Schematic....................................................................................... 3
3 RC Charging Rate........................................................................................................... 5
4 J8 Connection for Single-Supply Operation.............................................................................. 7
5 J8 Connection for Dual Supply Operation................................................................................ 8
6 Common-Mode Rejection Ratio (CMRR) Measurement ±15-V Supplies, 1-VRMS Input, 90-kHz MBW........... 9
7 THD+N vs. Amplitude Measurement ±15-V Supplies, 1-kHz Output, 22-kHz MBW................................ 9
8 THD+N vs. Frequency Measurement with 1 VRMS Output ±15-V Supplies, 1-VRMS Output, 90-kHz MBW...... 10
9 THD+N vs. Frequency Measurement With 10 VRMS Output ±15-V Supplies, 10-VRMS Output, 90-kHz MBW .. 10
10 FFT Measurement 1 kHz, 10-VRMS Output .............................................................................. 11
11 Top Layer PCB Layout .................................................................................................... 12
12 Bottom Layer PCB Layout ................................................................................................ 13
13 Schematic ................................................................................................................... 14
List of Tables
1 INA1651EVM Measured Performance Summary ....................................................................... 3
2 Final Capacitor Voltage..................................................................................................... 5
3 INA1651EVM Bill of Materials ............................................................................................ 15
Trademarks
SoundPlus is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.

+
±
+
±
VCC
VEE
IN+ A
COM A
IN- A
OUT A
VREF A
VMID (IN)
VMID (OUT)
VCC VEE
VCC VEE
R4
C9
C6 C11
R1
R5
C7
+ INPUT
- INPUT
C10
J8
R2 C8
R3
OUTPUT
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INA1651EVM SoundPlus™ High Common-Mode Rejection Line Receiver
Evaluation Module
1 Introduction
The INA1651 is a high common-mode rejection audio line receiver from the SoundPlus line of audio
amplifier products from Texas Instruments. For a full list of electrical characteristics of the INA1651,
please refer to the INA1651 product data sheet (INA165x SoundPlus™ High Common-Mode Rejection
Line Receivers).
2 EVM Measured Performance Summary
A summary of the INA1651EVM performance specifications is provided in Table 1. Specifications are
given for a supply voltage of VS= ±15 V at an ambient temperature of 25°C, unless otherwise noted.
Table 1. INA1651EVM Measured Performance Summary
Specification Test Conditions Measured Performance
Common-Mode Rejection Ratio (CMRR) VIN = 1 VRMS at 1 kHz –90 dB
THD+N at 1 kHz VIN = 22 dBu –121 dB
Second Harmonic VOUT = 10 VRMS, F = 1 kHz –142.86 dBc
Start-Up Time 1.5 s
3 Modifications
This EVM is designed to provide access to the features of and measure the performance of the INA1651.
Modifications of the INA1651EVM can be made and include; adjusting the ac-coupled corner frequency,
filtering the VMID (IN) pin, adjusting the start-up time, and increasing the common-mode input impedance.
A simplified schematic of the INA1651EVM is displayed in Figure 2. For a full schematic of the
INA1651EVM, see Figure 13.
Figure 2. Simplified INA1651EVM Schematic

0
f1
c _ VMID 2 250k C1
S u : u
R3
Attenuation R R
2 3

8
f1
c _out 2 (R R ) C
2 3
S u  u
n
f1
c _in C R
7 i
S u u
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3.1 AC-Coupled Corner Frequency
Capacitors C7 and C9 provide the option to ac couple the input of the INA1651 and capacitor C8 provides
the option to ac couple the output of the INA1651. Equation 1 calculates the high pass corner frequency of
input A and input B due to capacitors, C7 and C9 on the input.
where
• C7= C9
• RIN is the differential input impedance of the INA1651 (1)
Equation 2 calculates the high-pass corner frequency due to capacitor C8 and resistors R2 and R3 on the
output.
(2)
Resistors R2 and R3 form a voltage divider on the output of the INA1651 and will attenuate the output
signal. Equation 3 calculates the attenuation on the INA1651 output.
(3)
3.2 Filtering the VMID (IN) Pin
Capacitor C10 provides an option to filter the input to the internal reference buffer, VMID (IN). Equation 4
calculates the cut-off frequency due to C10.
(4)

Z CC
1
V V 100 mV
2
³ +
Time Constants (WRC)
Final Capacitor Voltage ()
0 1 2 3 4 5 6
0
10
20
30
40
50
60
70
80
90
100
D001
RC 10
250k CW : u
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3.3 Start-Up Time
Capacitor C10 increases the settling time of the VMID (OUT) pin due to the resistance of the internal
voltage divider for VMID (IN) and C10 creating an RC time constant. Equation 5 calculates one RC time
constant.
(5)
Figure 3 displays the rate at which an RC circuit charges to its final value. Notice at one time constant, the
voltage across the capacitor is at 63.2% of its final value.
Figure 3. RC Charging Rate
Table 2 shows the final capacitor voltage at multiple time constants.
Table 2. Final Capacitor Voltage
Time Constant (τRC) Final Capacitor Voltage (%)
1 63.2%
2 86.4%
3 95.0%
4 98.1%
5 99.3%
6 99.7%
To decrease the settling time of the VMID (OUT) voltage the Zener diode, D1, can be populated. The
Zener voltage of the diode should be chosen to be greater than 100 mV more than one half of the supply
voltage. Equation 6 calculates the recommended Zener voltage of the diode (Vz). Note that due to the
leakage current of the Zener diode interacting with the internal voltage divider resistance an error may be
seen on the VMID (OUT) pin.
(6)
3.4 Increasing the Common-Mode Input Impedance
The high CMRR of many line receivers can be degraded by source impedance mismatches in the system.
Resistor R4 provides an option to increase the common-mode input impedance of the INA1651 to reduce
the effects of source impedance mismatch. For an explanation on the effects of increasing the common-
mode input impedance, refer to section 8.1.2 of the INA1651 product data sheet (SBOS818).

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4 Test Setup and Results
This section describes how to properly connect, set up, and use the INA1651EVM. This section also
includes measured data of the INA1651EVM to display typical performance of the INA1651EVM.
Measurements include:
• Common-mode rejection ratio (CMRR)
• THD+N vs. Amplitude
• THD+N vs. Frequency
• Fast-Fourier Transform (FFT)
The THD+N vs. Amplitude,THD+N vs. Frequency, and FFT measurements were taken using an Audio
Precision APx555. All measurements used ±15-V supplies at an ambient temperature of 25 °C.
4.1 Power Supply Connections
The power supply connections for the INA1651EVM are provided through the use of the banana jacks or
test points located at the top of the EVM. The positive power supply connections are labeled as VCC, the
negative power supply connections are labeled as VEE, and the ground connections are labeled as GND.
For the minimum and maximum supply voltages of the INA1651EVM, refer to the INA1651 product data
sheet (SBOS818).
4.2 Input Connections
Input signals for the input are applied to the INA1651EVM through the use of the female XLR connector
J1 or terminal block J3. The female XLR connector follows the standard female XLR pin out with pin 1
connected to ground, pin 2 connected to the positive input, and pin 3 connected to the negative input. The
terminal block connections are labeled as +IN for the positive input, -IN for the negative input, and GND
for the ground connection.
4.3 Output Connections
The right and left channel output connections are provided through BNC connectors, J7 and J8, RCA
jacks, J9 and J10, and test points TP3 and TP5, respectively. The right channel outputs are labeled as
RIGHT OUTPUT and the left channel outputs are labeled as LEFT OUTPUT. The RCA jacks provide a
connection to a load while the BNC connectors and test points provide a way to measure the performance
of the INA1651 while a load is connected.

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4.4 REF A and COM A
Jumper J8 provides the option to connect pins VREF A and COM A to ground or VMID (OUT). In single
supply operation, place a shunt in the upper position (pins 2 to 3) of J8, as indicated by the red box in
Figure 4, to connect VREF A and COM A pins to VMID (OUT).
Figure 4. J8 Connection for Single-Supply Operation
For dual-supply operation, place a shunt in the lower position (pins 1 to 2) of J8, as indicated by the red
box in Figure 5, to connect VREF A and COM A pins to ground (GND).

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Figure 5. J8 Connection for Dual Supply Operation

Output Amplitude (VRMS)
Total Harmonic Distortion + Noise (%)
0.0005 0.001 0.01 0.1 1 10 2020
5E-5
0.0001
0.001
0.01
0.1
1
10
Frequency (Hz)
Gain (dB)
10 100 1000 10000 100000
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20 CMRR
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4.5 Common-Mode Rejection Ratio
The common-mode rejection ratio measurement was performed by applying a 1-Vrms common-mode
signal to the input and measuring the gain of the signal at the output. The frequency of the input signal
was swept from 20 Hz to 90 kHz, and the measurement bandwidth of the Audio Precision APx555 was set
to 90 kHz. Figure 6 shows a measurement of the CMRR.
Figure 6. Common-Mode Rejection Ratio (CMRR) Measurement
±15-V Supplies, 1-VRMS Input, 90-kHz MBW
4.6 THD+N vs. Amplitude
The THD+N vs. Amplitude measurement was performed by sweeping the output signal amplitude from
1 mVRMS to 13 VRMS at a frequency of 1 kHz. The measurement bandwidth of the Audio Precision APx555
was set to 22 kHz. Figure 7 shows a measurement of the THD+N vs. Amplitude.
Figure 7. THD+N vs. Amplitude Measurement
±15-V Supplies, 1-kHz Output, 22-kHz MBW

Frequency (Hz)
Total Harmonic Distortion + Noise (%)
20 30 50 70100 200300 500 1000 2000 5000 10000 20000 5000050000
0.0001
0.0002
0.0003
0.0005
0.0007
0.001
0.002
0.003
0.0050.005 THD+N (%)
Frequency (Hz)
Total Harmonic Distortion + Noise (%)
20 100 1000 10000 5000050000
0.0001
0.001
0.0050.005
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4.7 THD+N vs. Frequency
The THD+N vs. Frequency measurements were performed by sweeping the input signal from 20 Hz to
20 kHz with the measurement bandwidth of the Audio Precision APx555 set to 90 kHz. Figure 8 shows the
THD+N vs. Frequency measurement with an amplitude of 1 VRMS on the output of the INA1651. Note that
capacitor C8 on the output of the INA1651 can increase distortion at low frequencies due to non-linear
effects of the capacitor. Therefore, capacitor C8 is bypassed in these tests by a shunt installed across
jumper J5.
Figure 8. THD+N vs. Frequency Measurement with 1 VRMS Output
±15-V Supplies, 1-VRMS Output, 90-kHz MBW
Figure 9 shows the THD+N vs. Frequency measurement with an amplitude of 10 VRMS on the output of the
INA1651.
Figure 9. THD+N vs. Frequency Measurement With 10 VRMS Output
±15-V Supplies, 10-VRMS Output, 90-kHz MBW