Texas Instruments AN-1622 LM49100 User Manual
1 Quick Start Guide
1. Connect the I2C signal generation and interface board to a computer’s parallel port.
2. Apply 2.7V to 5.5V power supply’s positive output to the “VDD” pin on jumper “VDD GND”. Connect
the power supply’s ground return to the “GND” pin also on the aforementioned jumper.
3. Connect the supplied 6-wire (one pin is a No Connect) cable between the I2C signal generation and
interface board and the 6-pin connector (I2C Interface; one pin is a No Connect) on the LM49100
demonstration board. If logic levels other than those set by VDDare required, jumper J1 needs to be
connected and a separate supply applied to the 2–pin header with the I2CVDD pin, with respect to
ground.
4. Headphone amplifier output mode: Apply a stereo input audio signal to jumpers Left Input and Right
Input. Apply the sources’ +input pins and GND pins, respectively, to the demonstration board.
5. Connect a load (≥16Ω) to header HPL (left headphone) and another load (≥16Ω) to header HPR (right
headphone). The HPL pin and HPR pin carries the output signals from the two amplifiers, and each of
the other pins connecting to ground making this configuration single-ended connections.
6. Differential mono amplifier output mode: Apply a mono differential input audio signal to jumper Mono
Input. Apply the sources’ +input and –input to the middle two pins of the 4-pin jumper. The two outer
pins are connected to ground, which are used when the mono input is configured as single-ended
instead of differential.
7. Connect the 32Ω load across the two pins (differential) of the Speaker jumper on the demonstration
board.
8. Apply power. Make measurements. Enjoy the sound.
User's Guide
SNAA043A–October 2007–Revised May 2013
AN-1622 LM49100 Evaluation Board»
2 Introduction
To help you investigate and evaluate the LM49100's performance and capabilities, a fully populated
demonstration board is available from the Texas Instruments Audio Products Group. This board is shown
in Figure 1. Connected to an external power supply (2.7V to 5.5V), a signal source and an I2C controller
(or signal source), the LM49100 demonstration board easily demonstrate the amplifier's features.
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General Description
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3 General Description
The LM49100 is a fully integrated audio subsystem capable of delivering 1.275W of continuous average
power into a mono 8Ω bridged-tied load (BTL) with 1% THD + N and with a 5V power supply. The
LM49100 also has a stereo true-ground headphone amplifier capable of 50mW per channel of continuous
average power into a 32Ω single-ended (SE) loads with 1% THD + N.
The LM49100 has three input channels. One pair of SE inputs can be used with a stereo signal. The other
input channel is fully differential and may be used with a mono input signal. The LM49100 features a 32step digital volume control and ten distinct output modes. The mixer, volume control, and device mode
select are controlled through an I2C compatible interface.
Thermal overload protection prevent the device from being damaged during fault conditions. Superior click
and pop suppression eliminates audible transients on power-up/down and during shutdown.
4 Operating Conditions
Temperature Range
T
≤ TA≤ T
MIN
Supply Voltage VDDLS 2.7V ≤ VDDLS ≤ 5.5V
Supply Voltage VDDHP 2.4 V ≤ VDDHP ≤ 2.9V
I2C Voltage (VDDI2C ) 1.7V ≤ VDDI2C ≤ 5.5V
Temperature Range –40°C ≤ TA≤ 85°C
MAX
Figure 1. LM49100 Demonstration Board
−40°C ≤ TA≤ +85°C
VDDHP ≤ VDDLS
VDDI2C ≤ VDDLS
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5 Board Features
The LM49100 demonstration board has all of the necessary connections, using 0.100” headers, to apply
the power supply voltage, the audio input signals, and the I2C signal inputs. The amplified audio signal is
available on both a stereo headphone jack and auxiliary output connections.
Also included with the demonstration board is an I2C signal generation board and software. With this
board and the software, the user can easily control the LM49100’s, shutdown function, mute, and stereo
volume control. Figure 2 shows the software’s graphical user interface.
Board Features
6 Schematic
Figure 3 shows the LM49100 Demonstration Board schematic. Refer to Table 1 for a list of the
connections and their functions.
Figure 2. LM49100 Software User's Interface
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Mixer
&
Mode Select
Mono Input
-60 dB - +12 dB
Left Input
-54 dB - +18 dB
Right Input
-54 dB - +18 dB
I2C
Interface
Class AB
+6 dB
I2C
BUS
V
IH
V
IL
MINP
MINN
LIN
RIN
SDA
SCL
ADDR
GND
HPR
HPL
GND
LS-
LS+
VDDLS
V
DD
Audio
Input
Audio
Input
Audio
Input
VDDCP
Charge Pump
VSSHP
VSSCP
C1PC1N
GNDCP
Bias
Click/Pop
Suppresion
BYPASS
0 dB
-12 dB
-18 dB
-24 dB
0 dB
-12 dB
-18 dB
-24 dB
2.2 PF 0.1 PF
+
GNDS
VDDHP
VDDCP
4.7 PF
1 PF
1 P
F
0.22 PF
0.22 P
F
2.2 PF
0.1 PF
+
+
CAV
SS
2.2 PF
VDDI2C
C
B
2.2 P
F
V
DD
C
1
VDDI2C
C
IN
C
IN
C
IN
C
IN
Connections
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7 Connections
Connecting to the world is accomplished through the 0.100” headers on the LM49100 demonstration
board. The functions of the different headers are detailed in Table 1.
Header or Jumper Designation Function or Use
Figure 3. LM49100 Demonstration Board Schematic
Table 1. LM49100 Demonstration Board Connections
VDD/GND Main power supply and ground for the demonstration board.
V
/GND Headphone power supply for the headphone amplifier which creates split supplies: for the
DDHP
J1 A shorted J1 connects VDDdirectly to I2CVDD. An opened J1 disconnects VDDand I2CVDD. If
I2CV
DD
Right Input This is the connection to the amplifier’s single-ended right channel input.
Left Input This is the connection to the amplifier’s single-ended left channel input.
positive voltage is converted by switch capacitor creating a negative voltage of equal
magnitude.
open, a separate power supply connected to I2CVDD/GND header must be applied.
Header to apply an independent I2C power supply when J1 is open.
Mono Input This is the connection to the amplifier’s differential or single-ended left/right mono input.
The center two pins are the differential inputs, or single-ended inputs, while the outside
pins are the grounds.
Address Setting Used to set the address of the device. Normally set at “Low” on the demonstration board.
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Table 1. LM49100 Demonstration Board Connections (continued)
Header or Jumper Designation Function or Use
I2C Interface This is the input connection for the I2C serial clock and serial data signals. The
demonstration board has an adjacent I2C label identifying each pin.
Speaker Two-pin header used to connect the “+” and “-“ terminals of the mono speaker.
HPR This is the connection to the amplifier’s single-ended, ground referenced right channel
output. The “HPR” label refers to the output pin and “GND” is the corresponding ground.
HPL This is the connection to the amplifier’s single-ended, ground referenced left channel
output. The “HPL” label refers to the output pin and “GND” is the corresponding ground.
8 Power Supply Sequencing
The LM49100 uses two power supply voltages: VDDfor the analog circuitry and I2CVDD, which defines the
digital control logic high voltage level. To ensure proper functionality, apply VDDfirst, followed by I2CVDD. If
one power supply is used, VDDand I2CVDDcan be connected together. The part will power-up with both
channels shutdown, the volume control set to minimum, and the mute function active.
9 I2C Signal Generation Board and Software
The I2C signal generation and interface board, along with the LM49100 software, will generate the address
byte and the data byte used in the I2C control data transaction. To use the I2C signal generation and
interface board, please plug it into a PC’s parallel port (on either a notebook or a desktop computer).
The software comes with an installer. To install, unzip the file titled “LM49100_Software.” After the file
unzips, double-click the “setup.exe” file. After it launches, follow the installer’s instructions. Setup will
create a folder named “LM49100” in the “Program” folder on the “C” disk (if the default is used) along with
a shortcut of the same name in the “Programs” folder in the “Start” menu.
The LM49100 program includes controls for the amplifier’s volume control, individual channel shutdown,
and the mute function. The control program's on-screen user interface is shown in Figure 2.
The Default button is used to return the LM49100 to its power-on reset state: minimum volume setting,
shutdown on both amplifiers active, and mute active.
The LM49100’s stereo VOLUME CONTROL has 32 steps and a gain range of –76dB to 18dB. It is
controlled using the slider located at the bottom of the program’s window. Each time the slider is moved
from one tick mark to another, the program updates the amplifier’s volume control.
LEFT CHANNEL, BOTH CHANNELS, and RIGHT CHANNEL controls each have two buttons. For the
left and right channel control, the “ON” button activates its respective channel, whereas the “OFF” button
places its respective channel in shutdown mode. Selecting the BOTH CHANNELS “ON” button
simultaneously activates both channels, whereas selecting the “OFF” button places channels in shutdown
mode.
Power Supply Sequencing
10 PCB Layout Guidelines
This section provides general practical guidelines for PCB layouts that use various power and ground
traces. Designers should note that these are only "rule-of-thumb" recommendations and the actual results
are predicated on the final layout.
10.1 Power and Ground Circuits
Star trace routing techniques (returning individual traces back to a central point rather than daisy chaining
traces together in a serial manner) can have a major positive impact on low-level signal performance. Star
trace routing refers to using individual traces that radiate from a signal point to feed power and ground to
each circuit or even device. This technique may require greater design time, but should not increase the
final price of the board.
For good THD + N and low noise performance and to ensure correct power-on behavior at the maximum
allowed supply voltage, a local 2.2μF power supply bypass capacitor should be connected as physically
close as possible to the VDDLS pin.
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Bill of Materials
10.2 Avoiding Typical Design/Layout Problems
Avoid ground loops or running digital and analog traces parallel to each other (side-by-side) on the same
PCB layer. When traces must cross over each other, do so at 90 degrees. Running digital and analog
traces at 90 degrees to each other from the top to the bottom side as much as possible will minimize
capacitive noise coupling and crosstalk.
11 Bill of Materials
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Designator Part Description Value Package Type Manufacturer Manufacturer's
C1 Tantalum Capacitor 2.2μF 1206
CAVSS Tantalum Capacitor 2.2μF 1206
CBYPASS Tantalum Capacitor 2.2μF 1206
CCPUMP1 Tantalum Capacitor 4.7μF 1206
CCPUMP2 Multilayer Ceramic Capacitor 0.1μF 0805
CINL Multilayer Ceramic Capacitor 0.22μF 0805
CINR Multilayer Ceramic Capacitor 2.2μF 0805
CMINN Multilayer Ceramic Capacitor 1μF 0805
CMINP Multilayer Ceramic Capacitor 1μF 0805
CSUPPLY1 Tantalum Capacitor 2.2μF 1206
CSUPPLY2 Multilayer Ceramic Capacitor 0.1μF 0805
HPL 2–pin header, 100 mil pitch 1x2 Header
HPR 2–pin header, 100 mil pitch 1x2 Header
I2C 6–pin 6–pin header, 100 mil pitch 2x3 Header
Header
Left Input 2–pin header, 100 mil pitch 1x2 Header
Mono Input 4–pin header, 100 mil pitch 1x2 Header
Right Input 2–pin header, 100 mil pitch 1x2 Header
Speaker 2–pin header, 100 mil pitch 1x2 Header
Stereo Headphone Jack
Headphone Jack
V
DD
U1 with a True-Ground Headphone Texas Instruments LM49100
2–pin header, 100 mil pitch 1x2 Header
Mono Class AB Audio Subsystem
Amplifier
Part Number
12 Demonstration Board PCB Layout
NOTE: The LM49100 is controlled through an I2C compatible interface. The I2C chip address is 0xF8
(ADR pin = 0) or 0xFAh (ADDR pin = 1).
Figure 4 through Figure 9 show the different layers used to create the LM49100 four-layer demonstration
board. Figure 4 is the silkscreen that shows parts location, Figure 5 is the top layer, Figure 6 is the upper
inner layer, Figure 7 is the lower middle layer, Figure 8 is the bottom layer, and Figure 9 is the bottom
silkscreen layer.
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