LM49101, LM49101TMEVAL

www.ti.com

SNAS475A – MARCH 2009 – REVISED APRIL 2013

GAMP_SD BIT

The GAMP_SD bit allows for reduced power consumption. When set to '1' the gain amplifiers on unused inputs

will be shutdown saving approximately 0.4mA per input in shutdown. For example, in Mode 1 only the mono

inputs are in use. Setting GAMP_SD to '1' will shut down the gain amplifiers for the left and right inputs reducing

current draw from the VDDLS supply by approximately 0.8mA. The GAMP_SD bit does not need to be set each

time when changing modes as the LM49101 will automatically activate and deactivate the needed inputs based

on the mode selected.

When operating with GAMP_SD set to '1', a transient may be observed on the outputs when changing modes.

During power up, the LM49101 uses a start up sequence to eliminate any pops and clicks on the outputs. The

volume control circuitry is powered up first followed by the other internal circuitry with the output amplifiers being

powered up last. If a mode change requires a gain amplifier to turn on then a potential transient may be created

that is amplified on the already active outputs. To eliminate unwanted noise on the outputs the Power_On bit

should be used to turn off the LM49101 before changing modes, perform a mode change, then turn the LM49101

back on. This procedure will cause the LM49101 to follow the start up sequence.

LS (EP_MODE) BIT

The LS (EP_Mode) bit selects the amount of bias current in the loudspeaker amplifier. Setting the LS (EP_Mode)

bit to a '1' will reduce the amount of current from the VDDLS supply by approximately 0.5mA. The THD

performance of the loudspeaker amplifier will be reduced as a result of lower bias current. See the performance

graphs in Typical Performance Characteristics.

TURN_ON_TIME BIT

The Turn_On_Time bit determines the delay time from the Power_On bit set to '1' and the internal circuits ready.

For input capacitor values up to 0.47

μF the Turn_On_Time bit can be set to fast mode by setting the bit to a '1'.

When the input capacitor values are larger than 0.47

μF then the Turn_On_Time bit should be set to '0' for normal

turn-on time and higher delay. This allows sufficient time to charge the input capacitors to the ½ VDDLS bias

voltage.

POWER_ON BIT

The Power_On bit is the master control bit to activate or deactivate the LM49101. All registers can be loaded

independent of the Power_On bit setting as long as the IC is powered correctly. Cycling the Power_On bit does

not change the values of any registers nor return all bits to the default power on value of zero. The Power_On bit

only determines whether the IC is on or off.

EP BYPASS BIT

The EP Bypass bit is used to set the LM49101 to earpiece mode. When this bit is set the analog switch is

activated and the rest of the IC blocks except for the I2C circuitry will go into shutdown for minimal current

consumption.

HPR_SD BIT

The HPR_SD bit will deactivate the right headphone output amplifier. This bit is provided to reduce power

consumption when only one headphone output is needed.

MODE_CONTROL BITS

The LM49101 includes a comprehensive mixer multiplexer controlled through the I2C interface. The

mixer/multiplexer allows any input combination to appear on any output of LM49101. Multiple input paths can be

selected simultaneously. Under these conditions, the selected inputs are mixed together and output on the

selected channel. Table 5 shows how the input signals are mixed together for each possible input selection.

Copyright © 2009–2013, Texas Instruments Incorporated

Submit Documentation Feedback

21

Product Folder Links: LM49101 LM49101TMEVAL