TDA7850 STMicroelectronics, TDA7850 Datasheet - Page 14

• Manufacturer Part Number: TDA7850
• Description: IC AMP QUAD BRIDGE FLEXIWATT25
• Manufacturer: STMicroelectronics
• Type: Class ABr

Specifications of TDA7850

• Output Type: 4-Channel (Quad)
• Max Output Power X Channels @ Load: 85W x 4 @ 2 Ohm
• Voltage - Supply: 8 V ~ 18 V
• Features: Mute, Short-Circuit and Thermal Protection, Standby
• Mounting Type: Through Hole
• Package / Case: 25-Flexiwatt (bent and staggered leads)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application hints
4
4.1
4.2
4.3
4.4
4.5
14/18
Application hints
Referred to the circuit of
SVR
Besides its contribution to the ripple rejection, the SVR capacitor governs the turn ON/OFF
time sequence and, consequently, plays an essential role in the pop optimization during
ON/OFF transients. To conveniently serve both needs, Its minimum recommended value
is 10µF.
Input stage
The TDA7850's inputs are ground-compatible and can stand very high input signals (±
8Vpk) without any performance degradation.
If the standard value for the input capacitors (0.1µF) is adopted, the low frequency cut-off
will amount to 16 Hz.
Standby and muting
Standby and Muting facilities are both CMOS compatible. In absence of true CMOS ports or
microprocessors, a direct connection to Vs of these two pins is admissible but a 470kΩ
equivalent resistance should be present between the power supply and the muting and
ST-BY pins.
R-C cells have always to be used in order to smooth down the transitions for preventing any
audible transient noises.
About the standby, the time constant to be assigned in order to obtain a virtually pop-free
transition has to be slower than 2.5 V/ms.
DC offset detector
The TDA7850 integrates a DC offset detector to avoid that an anomalous DC offset on the
inputs of the amplifier may be multiplied by the gain and result in a dangerous large offset on
the outputs which may lead to speakers damage for overheating. The feature is enabled by
the MUTE pin (according to table 3) and works with the amplifier unmuted and with no signal
on the inputs.
The DC offset detection is signaled out on the HSD pin. To ensure the correct functionality of
the Offset Detector it is necessary to connect a pulldown 10 kW resistor between HSD and
ground.
Heatsink definition
Under normal usage (4 Ohm speakers) the heatsink's thermal requirements have to be
deduced from
music/speech programmes are played out. Noise with gaussian-distributed amplitude was
employed for this simulation. Based on that, frequent clipping occurrence (worst-case) will
cause P
heatsink's thermal resistance should be approximately 2°C/W. This would avoid any thermal
shutdown occurrence even after long-term and full-volume operation.
diss
= 26 W. Assuming T
Figure
18, which reports the simulated power dissipation when real
Figure
amb
2.
= 70 °C and T
CHIP
= 150 °C as boundary conditions, the
TDA7850