TDF8591TH datasheet(6/34 Pages) NXP

6 / 34 page

TDF8591TH_1

Product data sheet

Rev. 01 — 5 March 2008

6 of 34

NXP Semiconductors

TDF8591TH

× 100 W SE (4 Ω) or 1 × 310 W BTL (4 Ω) class-D ampliﬁer

If two or more class-D ampliﬁers are used in the same audio application, it is

recommended to synchronize the switching frequency of all devices to an external clock

(see Section 12.3).

6.4 Protections

The following protections are included in TDF8591TH:

• Thermal Foldback (TF)

• OverTemperature Protection (OTP)

• OverCurrent Protection (OCP)

• Window Protection (WP)

• Supply voltage protections

– UnderVoltage Protection (UVP)

– OverVoltage Protection (OVP)

– Unbalance Protection (UBP)

The reaction of the device on the different fault conditions differs per protection and is

described in Section 6.4.1 to Section 6.4.5.

6.4.1 Thermal foldback

If the junction temperature Tj > 145 °C, then the TF gradually reduced the gain, resulting in

a smaller output signal and less dissipation. At Tj = 155 °C the outputs are fully muted.

6.4.2 Overtemperature protection

If Tj > 160 °C, then the OTP will shut down the power stage immediately.

6.4.3 Overcurrent protection

The OCP will detect a short-circuit between the loudspeaker terminals or if one of the

loudspeaker terminals is short-circuited to one of the supply lines.

If the output current tends to exceed the maximum output current of 12 A, the output

voltage of the TDF8591TH will be regulated to a level where the maximum output current

is limited to 12 A while the ampliﬁer outputs remain switching, the ampliﬁer does not shut

down. When this active current limiting continues longer than a time

τ (see Figure 5) the

capacitor on pin DIAG is discharged below a threshold value and the TDF8591TH shuts

down. Activation of current limiting and the triggering of the OCP is observed at pin DIAG

(see Figure 5).

A maximum value for the capacitor on pin DIAG is 47 pF. The reference voltage on pin

DIAG is VSSA. Pin DIAG should not be connected to an external pull-up.

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