Connections
Connecting to the world is accomplished through the 100mil
headers on the LM4985 demonstration board. The functions
of the different headers are detailed in Table 1.
TABLE 1. LM4985 Demonstration Board Connections
Jumper Designation
Function or Use
JP1
Power supply connection. Connect an external power supply’s
positive voltage source to the JP1 pin labeled “+” and the supply’s
ground source to the pin labeled “-.”
JP2
If an external I
2
C power supply voltage is used, connect this
supply’s positive voltage source to the JP2 pin labeled “+” and the
supply’s ground source to the pin labeled “-.” If no external supply
is used, leave this jumper’s pins unconnected.
JP3
This is the connection to the amplifier’s input A (labeled as the
“left” input on the demonstration board). Apply an external signal
source’s positive voltage to the JP3 pin labeled “+” and the signal
source’s ground reference to the pin labeled “-.”
JP4
This is the connection to the amplifier’s output A (labeled as the
“left” output on the demonstration board). Connect the JP4 pin
labeled “+” to the positive input of an external signal measurement
device. Connect the JP4 pin labeled “-” to the ground input of an
external signal measurement device. JP4’s pin labeled “+”
corresponds to the headphone jack’s “tip” connection. JP4’s pin
labeled “-“ corresponds to the headphone jack’s “sleeve” (or
ground) connection.
JP5
This is the connection to the amplifier’s input B (labeled as the
“right” input on the demonstration board). Apply an external signal
source’s positive voltage to the JP5 pin labeled “+” and the signal
source’s ground reference to the pin labeled “-.”
JP6
This is the connection to the amplifier’s output B (labeled as the
“right” output on the demonstration board). Connect the JP6 pin
labeled “+” to the positive input of an external signal measurement
device. Connect the JP6 pin labeled “-” to the ground input of an
external signal measurement device. JP6’s pin labeled “+”
corresponds to the headphone jack’s “sleeve” connection. JP6’s
pin labeled “-“corresponds to the headphone jack’s “sleeve” (or
ground) connection.
JP7 and JP9
Combined, these jumpers are used for the I
2
C signal inputs.
JP9-pin 1 is for the SDA signal, JP9-pin 2 is for the ADR signal,
and JP9-pin 3 is for the SCL signal. JP7-pin 1 is for an I
2
C VDD
supply voltage supplied by the I2C signal source and JP7-pin 2 is
for ground.
JP8
This three-pin jumper is used when either OCL or C-CUPL modes
are used. Short pins 1 and 2 together when the OCL mode is
selected. Short pins 2 and 3 together when the C-CUPL mode is
selected.
JP10
This jumper is used to short the right channel output capacitor C6
when the OCL mode is selected through the I
2
C digital interface.
When the LM4985 is used in the C–CUPL mode, leave this jumper
open.
JP11
This jumper is used to short the left channel output capacitor C5
when the OCL mode is selected through the I
2
C digital interface.
When the LM4985 is used in the C–CUPL mode, leave this jumper
open.
AN-1452
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