TDA8920C_15 Datasheet, PDF(10/39 Page) NXP Semiconductors

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TDA8920C_15 Datasheet, PDF (10/39 Pages) NXP Semiconductors – 2 X 110 W class-D power amplifier

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NXP Semiconductors

TDA8920C

2 Ã 110 W class-D power ampliï¬er

When OCP is activated, the power transistors are turned off. They are turned on again

during the next switching cycle. If the output current is still greater than the OCP threshold,

they will be immediately switched off again. This switching will continue until CPROT is fully

discharged. The ampliï¬er will then be switched off completely and a restart sequence

initiated.

After a ï¬xed period of 100 ms, the ampliï¬er will attempt to switch on again, but will fail if

the output current still exceeds the OCP threshold. The ampliï¬er will continue trying to

switch on every 100 ms. The average power dissipation will be low in this situation

because the duty cycle is low.

Switching the ampliï¬er on and off in this way will generate unwanted âaudio holesâ. This

can be avoided by increasing the value of CPROT (up to 220 pF) to delay ampliï¬er

switch-off. CPROT will also prevent the ampliï¬er switching off due to transient

frequency-dependent impedance drops at the speakers.

The ampliï¬er will switch on, and remain in Operating mode, once the overcurrent

condition has been removed. OCP ensures the TDA8920C ampliï¬er is fully protected

against short-circuit conditions while avoiding audio holes.

Table 4. Current limiting behavior during low output impedance conditions at different

values of CPROT

Type

VP VI (mV, p-p) f (Hz) CPROT PWM output stops

(V)

(pF) Short

Short

(Zth = 0 â¦) (Zth = 0.5 â¦) (Zth = 1 â¦)

TDA8920C

29.5 500

20 10 yes

yes

OVP[1]

1000 10 yes

yes

20 15 yes

yes

OVP[1]

1000 15 yes

1000 220 no

[1] OVP can be triggered by supply pumping; see Section 13.6.

8.3.3 Window Protection (WP)

Window Protection (WP) checks the conditions at the output terminals of the power stage

and is activated:

â¢ During the start-up sequence, when the TDA8920C is switching from Standby to

Mute.

Start-up will be interrupted If a short-circuit is detected between one of the output

terminals and pin VDDP1/VDDP2 or VSSP1/VSSP2. The TDA8920C will wait until the

short-circuit to the supply lines has been removed before resuming start-up. The short

circuit will not generate large currents because the short-circuit check is carried out

before the power stages are enabled.

â¢ When the ampliï¬er is shut down completely because the OCP circuit has detected a

short circuit to one of the supply lines.

WP will be activated when the ampliï¬er attempts to restart after 100 ms (see

Section 8.3.2). The ampliï¬er will not start-up again until the short circuit to the supply

lines has been removed.

TDA8920C_2

Product data sheet

Rev. 02 â 11 June 2009

10 of 39

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