TDA7571 Datasheet, PDF (14/21 Pages) STMicroelectronics – STPDACsw - Fully digital high efficiency power audio amplifier

Functions, pins and components description
TDA7571
4
Functions, pins and components description
4.1
Short circuit protection current calculation
Figure 5. Short circuit protection current diagram
Imos
TDA7571
Rp1 (typ=4.7kOhm)
Rsens
(not inductive resistor)
Typ. Values = 10 – 30 mOhm
to -Vs
Cfil (typ 2.2nF)
Rfil (typ. 100 Ohm)
Vrfil = Ispx1 x Rfil = 20mV Typ
SPx2 pin
Rp2
Vp=100mV Typ
comparator
SPx1 pin
I_lim
=
--------¹---------
Rsens
⎛
⎝
V_-----p_----x_----⋅_---(_--R_-----p_----1_-----+-----R_----p_----2_----)
Rp2
+
Vf
il_⎠⎞
I_lim
=
--------¹---------
Rsens
(
Vp
x
+
V
fil
)
← if Rp2 is not used
4.2
External thermal protection network
The purpose of this function is to sense critical points of the amplifier system, as example
the heatsink of the power transistors, avoiding too high temperature.
Through the external thermal warning pin (THWEXT, pin 37), a signal useful to reduce the
power dissipation reducing (as example) the output power and/or, in a system provided of
regulated power supply, reducing the voltage supply of the amplifier (±V_S) is present.
Example of external thermal protection circuitry
● Components:
– type: B57621 C621/100k/+
– Text = 10K
● Results (simulations):
– External thermal warning temperature intervention: 90 °C
– External thermal shut down temperature intervention: 100 °C
– External thermal shut down hysteresis: 6°C
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