STW5095 datasheet(19/73 Pages) STMICROELECTRONICS

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Functional description

STw5095

18/72

4.9

Analog output drivers

STw5095 provides 3 different analog signal outputs and 1 common mode reference output:

●

Line Out Drivers: it is a stereo differential output, it can be used as single-ended

output just by using the positive or negative pin. It can drive 1 k

Ω resistive load. The

load can be connected between the positive and negative pins or between one pin and

ground through a decoupling capacitor. The output gain is regulated with LOG bits in

CR7, in the range 0 to -18 dB, simultaneously for left and right channels. When used as

a single ended output the effective gain is 6 dB lower. It is muted with bit MUTELO in

CR19. The input signal of this stereo output can come from the analog mixer or directly

from MIC preamplifiers. The output Common Mode Voltage level is controlled with bits

VCML in CR19. The supply voltage of line out drivers is VCCP.

The Line Out Drivers are powered up with bits ENLOL and ENLOR in CR1. The output

pins are in high impedance state with a 180k

Ω pull-down resistor when the Line Out

Drivers are powered down.

●

Headphones Drivers: it is a stereo single ended output. It can drive 16 Ohm resistive

load and deliver up to 40 mW. The output gain is regulated with HPLG and HPRG bits

in CR8 and CR9 respectively, with a range of -40 to 6 dB. It is muted with bit MUTEHP

in CR19. The input signal of this stereo output comes from the analog mixer.The output

Common Mode Voltage is controlled with bits VCML in CR19. The supply voltage of

headphones drivers is VCCP.

The Headphones Drivers are powered up with bits ENHPL and ENHPR in CR2.The

output pins are in high impedance state when the Headphones Drivers are powered

down.

●

Common Mode Voltage Driver: it is a single ended output with output voltage value

selectable with bits VCML in CR19, from 1.2 V to 1.65 V in steps of 150 mV. The output

voltage should be set to the value closest to VCCP/2 to optimize output drivers

performance. The Common Mode Voltage Driver is designed to be connected to the

common pin of stereo headphones, so that decoupling capacitors are not needed at

HPL and HPR outputs. The supply voltage of the common mode voltage driver is

VCCP.

The Common Mode Voltage Driver is powered up with bit ENHPVCM in CR2.The

output pin is in high impedance state when the Common Mode Voltage Driver is

powered down.

●

Loudspeaker Driver: it is a monophonic differential output. It can drive 8

Ω resistive

load and deliver up to 500 mW to the load. The output gain is regulated with LSG bits in

CR7, in the range -24 to +6 dB. The input signal of the loudspeaker driver comes from

the analog mixers: bits LSSEL in CR29 select left channel, right channel, (L+R)/2

(mono) or mute. The output Common Mode Voltage is obtained with an internal voltage

divider from VCCLS and it is connected to CAPLS pin. The supply voltage of the

loudspeaker driver is VCCLS.

The Loudspeaker Driver is powered up with bit ENLS in CR2.The output pin is in high

impedance state when the Loudspeaker Driver is powered down.

Note:

Note on direct connection of VCCLS To the battery:

The voltage of batteries of handheld devices during charging is usually below 5.5 V, making

VCCLS supply pin suitable for a direct connection to the battery. In this case if STw5095 is

delivering the maximum power to the load and the ambient temperature is above 70 °C then

the simultaneous charging of the battery can overheat the device. A basic protection

scheme is implemented in STw5095 (activated with bit LSLIM in CR19): it limits the

maximum gain of the loudspeaker to -6 dB when VCCLS is above 4.2 V, and it removes the

limit for VCCLS below 4.0 V. The loudspeaker gain is left unchanged if it is set below -6 dB

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