LM49450: LM49450 NO OUTPUT SIGNAL

Hi, Antonio,

Welcome to E2E and thank you for your interest in our products!

I don't see any I2C communication line in both circuits schematic. The LM49450 requires of some I2C commands to be enabled. How do you configure the devices?

Best regards,
Luis Fernando Rodríguez S.

Hi Luis,

Thanks for the reply.

After trying, we realized that the problem, as you say, was the I2C. The connection is made through an embedded PC (QSEVEN, congatec).

Would it be possible to change the address to connect several LM49450 and that there isn't conflict?

Thanks.

Best regards.

Hi Luis,

We have to connect 4 LM49450 to the same device. In the datasheet it's indicated that the address is: 1111101. Is it possible to change it? To avoid conflicts.

Thank you.

Hello Luis,

Perfect! We will try with the TCA9544A.

Thank you.

Best regards.

Hello Luis,

We are testing only with one amplifier, but we don't have any output signal, we enable it using 0x00h register address, also we configure headphone and speaker to have maximun Gain (18 dB for headphones and 24 dB for speakers). And we continue having no output signal, is there any problem with our schematic or is only a configuration problem?

Thank you and best regards.

Hi, Antonio,

Is it possible to read the actual registers configuration? Which are the values that the device throws?

Thank you.

Best regards,
Luis Fernando Rodríguez S.

Registers configuration:

0x00 -> 0 We modify to 01 to enable (enable B0)

0x01 -> 0

0x02 -> 0x49 This is the DAC Clock configuration (We haven't touched anything, because it isn't supposed to be)

0x03 -> 0

0x04 -> 0

0x05 -> 0

0x06 -> 0

0x07 -> 0 Modified to change the gain. Example: 0xff

0x08 -> 0 Modified to change the gain. Example: 0xff

0x09 -> 0

0x0A -> 0

0x0B -> 0

0x0C -> 0

0x0D -> 0

0x0E -> 0

Thanks.

Best regards.

Hi, Antonio,

Just to confirm, are these values the registers that you read (not the ones that you wrote)? This is just to ensure that the device registers are written correctly.

Best regards,
Luis Fernando Rodríguez S.

Hi Luis,

Those values shown are read from the registers for the  first time. The only registers we modify are next:

Reg.       New_val              Old_Val

0x01           0x01                      0x00

0x07           0xff                       0x00

0x08           0xff                       0x00

Also, we are not sure if line-in (Reg. 0x00   Bit-B1) is need to be enabled, as we use as output Speakers or Headphones.

For more info:

Our project has an analog output (R and L) and we want to amplify the signal. So, we use INR (R) and INL (L) lines, as you can see at the schematic    sent (No DAC). When we use I2C we change, as mentioned, Reg 0x00, 0x07 and 0x08 to the new values and changed correctly.

As you can see at next picture… We have a doubt that belongs to the switching of Volume Control box with the two input analog signals, INR and INL. It looks like an I2C command has to be sent to make the switching, but we don’t know how… Have we missed something? Schematic or I2C commands/configuration.

Thanks.

Best regards.

Hi, Antonio,

It seems that there's an error in the datasheet and the register 0x00 doesn't include the bit B1. As shown in the table 1 ( http://www.ti.com/lit/ds/symlink/lm49450.pdf#page=26 ), this bit is related to the LINE_IN activity. So, it should be configured to change from the DAC to LINE_IN mode.

Could you try writing a '1' in B1 of register 0x00?

Please let me know how it results.

Best regards,
Luis Fernando Rodríguez S.

Hello Luis,

We try writting a '1' in B1 of 0x00, but we have the same problem.

Best regards.

Hello, Antonio,

Could you provide a capture of your input signal and the output level that you are facing?

In addition, could you provide details about how the outputs (speaker and headphone) look when the power supplies are enabled and when the registers are written?

Best regards,
Luis Fernando Rodríguez S.