Functions, pins and components description

TDA7571

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4

Functions, pins and components description

4.1

Short circuit protection current calculation

Figure 5.

Short circuit protection current diagram

← 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

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

Cfil (typ 2.2nF)

to -Vs

Rsens

(not inductive resistor)

Typ. Values = 10 – 30 mOhm

Rfil (typ. 100 Ohm)

Rp1 (typ=4.7kOhm)

Rp2

Vrfil = Ispx1 x Rfil = 20mV Typ

SPx1 pin

SPx2 pin

TDA7571

Vp=100mV Typ

comparator

Imos

I

lim

1

Rsens

------------------ Vpx

Rp1

Rp2

+

()

⋅

Rp2

--------------------------------------------------

Vfil

+

⎝⎠

⎛⎞

=

I

lim

1

Rsens

------------------ Vpx

Vfil

+

()

=