TS4985 datasheet(22/29 Pages) STMICROELECTRONICS

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Application Information

TS4985

22/29

Due to process tolerances, the maximum value of wake-up time could be establish by the graph

Figure 64.

Note:

Bypass capacitor Cb as also a tolerance of typically +/-20%. To calculate the wake-up time with

this tolerance, refer to the previous graph (considering for example for Cb = 1µF in the range of

0.8µF

≤ 1µF ≤ 1.2µF).

4.7

Shutdown time

When the standby command is set, the time required to put the two output stages in high

impedance and the internal circuitry in shutdown mode is a few microseconds.

Note:

In shutdown mode, Bypass pin and Vin- pin are short-circuited to ground by internal switches.

This allows for the quick discharge of the Cb and Cin capacitors.

4.8

Pop performance

Pop performance is intimately linked with the size of the input capacitor

Cin and the bias voltage

bypass capacitor

Cb.

The size of

Cin is dependent on the lower cut-off frequency and PSRR values requested. The

size of

Cb is dependent on THD+N and PSRR values requested at lower frequencies.

Moreover,

Cb determines the speed with which the amplifier turns ON. In order to reach near

zero pop and click, the equivalent input constant time is:

τin =(Rin+2kΩ)x Cin (s) with Rin ≥ 5kΩ

must not reach the

τin maximum value as indicated in the graph below in Figure 65.

Figure 63. Typical wake-up time vs. Cb

Figure 64. Maximum wake-up time vs. Cb

100

200

300

400

500

600

4.7

0.1

Tamb=25

°C

Vcc=2.6V

Vcc=3.3V

Vcc=5V

Bypass Capacitor Cb ( F)

100

200

300

400

500

600

Tamb=25

°C

4.7

0.1

Vcc=5V

Vcc=3.3V

Vcc=2.6V

Bypass Capacitor Cb ( F)

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