datasheetbank_Logo
Integrated circuits, Transistor, Semiconductors Search and Datasheet PDF Download Site

TS419-4IQT View Datasheet(PDF) - STMicroelectronics

Part Name
Description
View to exact match
TS419-4IQT
ST-Microelectronics
STMicroelectronics ST-Microelectronics
TS419-4IQT Datasheet PDF : 32 Pages
First Prev 21 22 23 24 25 26 27 28 29 30 Next Last
TS419-TS421
The efficiency is the ratio between the output
power and the power supply
η = POUT = π VPEAK
P supply 4 Vcc
The maximum theoretical value is reached when
Vpeak = Vcc, so
π = 78.5%
4
s Decoupling of the circuit
Two capacitors are needed to bypass properly the
TS419/TS421. A power supply bypass capacitor
CS and a bias voltage bypass capacitor CB.
CS has particular influence on the THD+N in the
high frequency region (above 7kHz) and an
indirect influence on power supply disturbances.
With 1µF, you can expect similar THD+N
performances to those shown in the datasheet.
In the high frequency region, if CS is lower than
1µF, it increases THD+N and disturbances on the
power supply rail are less filtered.
On the other hand, if CS is higher than 1µF, those
disturbances on the power supply rail are more
filtered.
CB has an influence on THD+N at lower
frequencies, but its function is critical to the final
result of PSRR (with input grounded and in the
lower frequency region).
If CB is lower than 1µF, THD+N increases at lower
frequencies and PSRR worsens.
If CB is higher than 1µF, the benefit on THD+N at
lower frequencies is small, but the benefit to PSRR
is substantial.
Note that CIN has a non-negligible effect on PSRR
at lower frequencies. The lower the value of CIN,
the higher the PSRR.
s Wake-up Time: TWU
When standby is released to put the device ON,
the bypass capacitor CB will not be charged
immediatly. As 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 wake-up time or TWU and typically
equal to:
TWU=0.15xCB (s) with CB in µF.
Due to process tolerances, the range of the
wake-up time is :
0.12xCb < TWU < 0.18xCB (s) with CB in µF
Note : When the standby command is set, the time
to put the device in shutdown mode is a few
microseconds.
s 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. The slower the speed is, the
softer the turn ON noise is.
The charge time of CB is directly proportional to
the internal generator resistance 150k..
Then, the charge time constant for CB is
τB = 150kxCB (s)
As CB is directly connected to the non-inverting
input (pin 2 & 3) and if we want to minimize, in
amplitude and duration, the output spike on Vout1
(pin 5), CIN must be charged faster than CB. The
equivalent charge time constant of CIN is:
τIN = (Rin+Rfeed)xCIN (s)
Thus we have the relation:
τIN < τB (s)
Proper respect of this relation allows to minimize
the pop noise.
Remark : Minimizing CIN and CB benefits both the
pop phenomena, and the cost and size of the
application.
s Application : Differential inputs BTL power
amplifier.
The schematic on figure 98, shows how to design
the TS419/21 to work in a differential input mode.
The gain of the amplifier is:
In order to reach optimal
G VDIFF
= 2 R2
R1
performances of the differential function, R1 and
R2 should be matched at 1% max.
28/32
 

Share Link: 

datasheetbank.com [ Privacy Policy ] [ Request Datasheet ] [ Contact Us ]