P
Dissipated + PO(average)
((1 Efficiency)
* 1)
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SLOS398E – DECEMBER 2002 – REVISED AUGUST 2010
SHORT-CIRCUIT PROTECTION
The TPA3001D1 has short-circuit protection circuitry on the outputs that prevents damage to the device during
output-to-output shorts, output-to-GND shorts, and output-to-VCC shorts. When a short-circuit is detected on the
outputs, the part immediately disables the output drive and enters into shutdown mode. This is a latched fault
and must be reset by cycling the voltage on the SHUTDOWN pin to a logic low and back to the logic high state
for normal operation. This clears the short-circuit flag and allows for normal operation if the short was removed. If
the short was not removed, the protection circuitry again activates.
Two Schottky diodes are required to provide short-circuit protection. The diodes should be placed as close to the
TPA3001D1 as possible, with the anodes connected to PGND and the cathodes connected to OUTP and OUTN
as shown in the application circuit schematic. The diodes should have a forward voltage rating of 0.5 V at a
minimum of 1-A output current and a dc blocking voltage rating of at least 30 V. The diodes must also be rated to
operate at a junction temperature of 150°C.
If short-circuit protection is not required, the Schottky diodes may be omitted.
THERMAL PROTECTION
Thermal protection on the TPA3001D1 prevents damage to the device when the internal die temperature
exceeds 150°C. There is a ±15°C tolerance on this trip point from device to device. Once the die temperature
exceeds the thermal set point, the device enters into the shutdown state and the outputs are disabled. This is not
a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 15°C. The device
begins normal operation at this point with no external system interaction.
THERMAL CONSIDERATION: OUTPUT POWER AND MAXIMUM AMBIENT TEMPERATURE
To calculate the maximum ambient temperature,
Equation 3 may be used:
TAmax = TJmax – qJAPDissipated
(3)
where: TJmax = 150°C
qJA = 1 / derating factor = 1 / 0.03333 = 30°C/W
(The derating factor for the 24-pin PWP package is given in the dissipation rating table.)
To estimate the power dissipation,
Equation 4 may be used:
(4)
Efficiency = ~85% for an 8-
load or = ~75% for a 4- load
Example: What is the maximum ambient temperature for an application that requires the TPA3001D1 to drive
10 W into an 8-
speaker?
PDissipated = 10 W × ((1 / 0.85) – 1) = 1.76 W
TAmax = 150°C – (30°C/W × 1.76 W) = 97.2°C
This calculation shows that the TPA3001D1 can drive 10 W into an 8-
speaker up to the absolute maximum
ambient temperature rating of 85°C, which must never be exceeded. Also, refer to
Figure 2, Figure 3, and
Figure 4 to determine the minimum load impedance for the desired output power.
GAIN SETTING VIA GAIN0 AND GAIN1 INPUTS
The gain of the TPA3001D1 is set by two input terminals, GAIN0 and GAIN1.
The gains listed in
Table 1 are realized by changing the taps on the input resistors inside the amplifier. This
causes the input impedance (ZI) to be dependent on the gain setting. The actual gain settings are controlled by
ratios of resistors, so the gain variation from part to part is small. However, the input impedance may shift by
30% due to shifts in the actual resistance of the input resistors.
For design purposes, the input network (discussed in the next section) should be designed assuming an input
impedance of 23 k
, which is the absolute minimum input impedance of the TPA3001D1. At the lower gain
settings, the input impedance could increase as high as 313 k
.
Copyright 2002–2010, Texas Instruments Incorporated
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