tda2500 Tripath Technology Inc., tda2500 Datasheet - Page 18

• Manufacturer Part Number: tda2500
• Description: Stereo Class-t Digital Audio Amplifier Driver Using Digital Power Processing Dpp
• Manufacturer: Tripath Technology Inc.

As stated in the Mute section above, a common cause of turn off pops can be attributed to the 5V supply
collapsing while the other supply rails are still present. On power down, mute should be activated (pulled
high) before the power supplies, especially the 5V, begin to collapse. A microcontroller supervisor, now
available from multiple manufacturers, is a good way to insure proper control of the mute during power
supply sequencing.
DC OFFSET
While the DC offset voltages that appear at the speaker terminals of a TDA2500 amplifier are typically
small, Tripath recommends that any offsets during operation be nulled out of the amplifier with a circuit
like the one shown connected to IN1 and IN2 in the Application/Test Circuit. It should be noted that the
DC voltage on the output of a TDA2500 amplifier with no load in mute will not be zero. This offset does
not need to be nulled. The output impedance of the amplifier in mute mode is approximately 40K:(R
1.0k:). This means that the DC voltage drops to essentially zero when a typical load is connected.
OVER-CURR ENT PROTEC TION
The TDA2500 has over-current protection circuitry to protect itself and the output transistors from short-
circuit conditions. The TDA2500 measures the voltage across a resistor, R
OCSxLP and OCSxLN) that is in series with each output MOSFET to detect an over-current condition. R
and R
operation. This implies connecting a trace directly from the resistor lead to the respective sense pin. No
other current or power supply connections should be made to the OCS pins of the TDA2500. Doing so
will result in false overcurrent events due to the IR losses of the PCB trace. See “Circuit Board Layout” in
Application Information for additional details.
When the voltage across R
output stages of its amplifiers. The occurrence of an over-current condition is latched in the TDA2500
and can be cleared by toggling the MUTE input or cycling power.
SETTING OVER-CURR ENT THRESHOLD
R
For example, to set an I
10m:.
As high-wattage resistors are usually only available in a few low-resistance values (10m:, 25m: and
50m:), R
R
It should be noted that the overcurrent trip level has a “duty cycle” dependence of roughly 2:1. This is due
to the half-wave current detection (with some filtering) nature of the protection circuit implemented on the
18
S
S
.
and R
OCR
I
R
where:
R
V
OC
OCR
TOC
OCR
S
OCR
are used to set the over-current threshold. The OCS pins must be Kelvin connected for proper
and R
= (4990 x (V
determine the value of the over-current threshold, I
= Over-current sense threshold voltage (See Electrical Characteristics Table)
= 0.97V typically
= (4990 x V
can be used to adjust for a particular over-current threshold using one of these values for
OCR
I
BIAS
are in :
OC
TOC
TOC
of 20A using a +/-90V supply, R
OCR
– I
)/(I
BIAS
OC
becomes greater than V
+/-60V
* R
* R
30PA
TABLE 1: Typical I
S
OCR
+ 4990 * I
)) / (R
OCR
BIAS
+/-70V
32PA
* R
)
S
)
TOC
BIAS
T r i p a t h T e c h n o l o g y , I n c . - T e c h n i c a l I n f o r m a t i o n
OCR
values for TDA2500
(typically 0.97) the TDA2500 will shut off the
= 13.006K: (use 13K:, 1%) and R
SC
33.5PA
+/-80V
:
TDA2500 – KL/ Rev. 0.9/05.05
S
(via OCSxHP, OCSxHN,
34.5PA
+/-90V
S
will be
F
B +
S