Texas Instruments INA1620EVM, Руководство пользователя, Страница: 5 / 24

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Modifications
5 SBOU205 – March 2018
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INA1620EVM Audio Amplifier Evaluation Module
3.2 Cutoff Frequency
This EVM provides the ability to filter the output of the INA1620. The cutoff frequency of the filter can be
calculated using
Equation 7 and Equation 8 .
given
• R
1
= R
7
, R
2
= R
6
, and C
1
= C
2
(7)
given
• R
13
= R
19
, R
15
= R
20
, and C
3
= C
4
(8)
If the internal resistors of the INA1620 are used instead, both R
2
and R
15
above are 1-k
Ω
resistors.
3.3 Phase Shift
The phase shift, Θ , is calculated using Equation 9 .
where
• ƒ is the maximum frequency of interest within the audio band
• ƒ
c
is the cutoff frequency discussed in Section 3.2 (9)
3.4 Alternative Uses for Internal Resistors
For most headphone amplifier applications, the internal thin-film resistors in the INA1620 are used as
shown in
Figure 1 . However, these resistors may be used for other purposes, if desired. The
INA1620EVM supports disconnecting each of the four matched resistor pairs for external use, as
described below.
Table 2. Jumper and Resistor Substitutions for Internal Resistor Reuse
INA1620 INTERNAL RESISTOR PAIR 0-
Ω
RESISTORS TO REMOVE 1-k
Ω
RESISTORS TO INSTALL
R1 (terminals R1A, R1B, R1C) R8, R9, R10 R6, R7
R2 (terminals R2A, R2B, R2C) R3, R4, R5 R1, R2
R3 (terminals R3A, R3B, R3C) R16, R17, R18 R19, R20
R4 (terminals R4A, R4B, R4C) R11, R12, R14 R13, R15
Table 2 shows the 0- Ω resistors that must be removed and 1-k Ω resistors that must be added in order to
use each internal resistor pair in the INA1620 separately. When the appropriate changes have been
made, the internal resistor pairs may be accessed on the corresponding connections on the EVM labelled
U1R1 A, B, and C, U1R2 A, B, and C, etc, as shown in
Figure 13 .