TS4998 datasheet(26/33 Pages) STMICROELECTRONICS

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Application information

TS4998

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4.9

Standby control and wake-up time tWU

The TS4998 has two dedicated standby pins (STBYL, STBYR). These pins allow to put

each channel in standby mode or active mode independently. The amplifier is designed to

reach close to zero pop when switching from one mode to the other.

When both channels are in standby (VSTBYL = VSTBYR = GND), the circuit is in shutdown

mode. When at least one of the two standby pins is released to put the device ON, the

bypass capacitor Cb starts to be charged. Because Cb is directly linked to the bias of the

amplifier, the bias will not work properly until the Cb voltage is correct. The time to reach this

voltage is called the wake-up time or tWU and is specified in Table 4 on page 5, with Cb=1µF.

During the wake-up phase, the TS4998 gain is close to zero. After the wake-up time, the

gain is released and set to its nominal value. If Cb has a value different from 1µF, then refer

to the graph in Figure 66 to establish the corresponding wake-up time.

When a channel is set to standby mode, the outputs of this channel are in high impedance

state.

Figure 66.

Typical startup time vs. bypass capacitor

4.10

Shutdown time

When the standby command is activated (both channels put into standby mode), the time

required to put the two output stages of each channel in high impedance and the internal

circuitry in shutdown mode is a few microseconds.

Note:

In shutdown mode when both channels are in standby, the Bypass pin and LIN+, LIN-, RIN+,

RIN- pins are shorted to ground by internal switches. This allows a quick discharge of Cb and

CIN capacitors.

4.11

Pop performance

Due to its fully differential structure, the pop performance of the TS4998 is close to perfect.

However, due to mismatching between internal resistors Rfeed, external resistors RIN and

0.00.5

1.01.5

2.02.5

3.03.5

4.04.5

100

Tamb=25

°C

Vcc=2.7V

Vcc=3.3V

Vcc=5V

Bypass Capacitor Cb (

μF)

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