TDA7570

Functions, pins and components description

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4.4

External thermal protection network

Example of external thermal protection circuitry

●

Components:

–

type: B57621 C621/100k/+

●

Results (simulations):

–

External thermal warning temperature intervention: 90 °C

–

External thermal shut down temperature intervention: 100 °C

–

External thermal shut down hysteresis: 6 °C

4.5

Gate driving network

The main purpose of the 27 Ohm resistors Rd-N-L, Rd-P-L, Rd-N-R and Rd-P-R are the

following:

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1) Dumping of the L-C equivalent circuit done by the parasitic inductance and

capacitance present in the circuit

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2) Reduction of the dv/dt of the Vgs and then reduction of the di/dt of the drain current

of the power MOS.

The R-C snubber network done by:

–

Rs-N-L, Cs-N-L

–Rs-P-L, Cs-P-L

–

Rs-N-R, Cs-N-R

–

Rs-P-R, Cs-P-R

Are in the direction to increase the dumping (point 1) and reduce the dv/dt (point 2.

The value of these components is also depending on the layout structure. With a reduction

of the parasitic inductance present in the P.C. board layout, in the region around the power

transistors, the value of these components can be reduced, giving advantage in terms of

THD, mainly at mid-high power levels, due to the reduction of the "dead zone".

The minimum suggested value of Rd-x-x is around 10

Ω, while, is some cases, Rs-x-x and

Cs-x-x can be removed.

4.6

External connections

●

CD, THWEXT, THWINT

These pins, if used, it must be connected to a pull-up resistor (>10k

Ω) connected to a

supply voltage referred to the receiver device (as example, a

μP). Max 10V.

●

MUTE - To have a soft mute-play and play-mute transition, an R-C network can be

applied (as example 47k

Ω, 1μF)

●

ST-BY - To avoid pop noise due to multiple ST-BY parasitic pulses, an R-C network can

be added (as example 47k

Ω, 0.1μF)

●

a reference voltage comprising between 12V to +Vs.