參數資料
型號: TS4984IQT
廠商: STMICROELECTRONICS
元件分類: 音頻/視頻放大
英文描述: 1 W, 2 CHANNEL, AUDIO AMPLIFIER, QCC16
封裝: 4 X 4 MM, 0.50 MM PITCH, LEAD FREE, TQFN-16
文件頁數: 16/29頁
文件大小: 901K
代理商: TS4984IQT
Application Information
TS4984
23/29
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:
tin =(Rin+2 k)x Cin (s) with Rin 5k
must not reach the
τin maximum value as indicated in the graph below in Figure 68.
By following previous rules, the TS4984 can reach near zero pop and click even with high gains such as
20 dB.
Example calculation
With Rin =22k and a 20 Hz, -3 db low cut-off frequency, Cin = 361 nF. So, Cin =390 nF with standard
value which gives a lower cut-off frequency equal to 18.5 Hz. In this case, (Rin +2 k)x Cin =9.36ms.
When referring to the previous graph, if Cb =1 F and Vcc = 5 V, we read 20 ms max. This value is twice
as high as our current value, thus we can state that pop and click will be reduced to its lowest value.
Minimizing both Cin and the gain benefits both the pop phenomena, and the cost and size of the
application.
Figure 68:
τin max. versus bypass capacitor
12
34
0
40
80
120
160
Vcc=5V
Vcc=3.3V
Vcc=2.6V
Tamb=25
°C
in
m
ax.
(m
s)
Bypass Capacitor Cb ( F)
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