2 × 40 W/2 Ω stereo BTL car radio power amplifier with
differential inputs and diagnostic outputs
Rev. 06 — 15 October 2007Product data sheet
1.General description
The TDA8566 is an integrated class-B output amplifier which is available in several
packages. TDA8566TH is contained in a 20-lead small outline plastic package. The
TDA8566TH1 is a 24-lead small outline plastic package which is pin compatible with the
I2C-bus controlled amplifier TDA1566TH for one board layout. TDA8566Q is a 17-pin
DIL-bent-SIL package.
The device contains 2 amplifiers in a Bridge-Tied Load (BTL) configuration. The output
power is 2 × 25 W in a 4 Ω load or 2 × 40 W in a 2 Ω load. It has a differential input stage
and 2 diagnostic outputs. The device is primarily developed for car radio applications.
2.Features
n Differential inputs
n Very high Common Mode Rejection Ratio (CMRR)
n High common mode input signal handling
n Requires very few external components
n High output power
n 4 Ω and 2 Ω load driving capability
n Low offset voltage at output
n Fixed gain
n Diagnostic facility (distortion, short-circuit and temperature pre-warning)
n Good ripple rejection
n Mode select switch (operating, mute and standby)
n Load dump protection
n Short-circuit proof to ground, to VP and across the load
n Low power dissipation in any short-circuit condition
n Thermally protected
n Reverse polarity safe
n Protected against electrostatic discharge
n No switch-on/switch-off plops
n Low thermal resistance
n TDA8566TH1 is pin compatible with TDA1566TH
NXP Semiconductors
3.Quick reference data
Table 1.Quick reference data
VP= 14.4 V; T
specified.
Symbol ParameterConditionsMinTypMaxUnit
V
P
I
ORM
I
q
I
stb
Z
i
P
o
SVRRsupply voltage ripple
α
cs
CMRRcommon mode rejection
G
v
V
n(o)
[1] The circuit is DC adjusted at VP= 6 V to 18 V and AC operating at VP= 8.5 V to 18 V.
[2] V
[3] Common mode rejection ratio measured at the output (over RL) with both inputs tied together;
[4] Noise measured in a bandwidth of 20 Hz to 20 kHz.
MODE14mode select switch input (standby/mute/operating)
DIAG15short-circuit and temperature pre-warning diagnostic output
IN2+16channel 2 input positive
IN2−17channel 2 input negative
13supply voltage 2
7.Functional description
The TDA8566 contains 2 identical amplifiers and can be used for BTL applications. The
gain of each amplifier is fixed at 26 dB. Special features of this device are:
• Mode select switch
• Clip detection
• Short-circuit diagnostic
• Temperature pre-warning
• Open-collector diagnostic outputs
• Differential inputs
…continued
7.1 Mode select switch (pin MODE)
•
Standby: low supply current
• Mute: input signal suppressed
• Operating: normal on condition
Since this pin has a very low input current (< 40 µA), a low-cost supply switch can be
applied. To avoid switch-on plops, it is advisable to keep the amplifier in the mute mode for
a period of ≥ 150 ms (charging the input capacitors at pins IN1+, IN1−, IN2+ and IN2−).
This can be realized by using a microcontroller or by using an external timing circuit as
illustrated in Figure 8.
7.2 Clip detection (pin CLIP)
When clipping occurs at one or more output stages, the dynamic distortion detector
becomes active and pin CLIP goes LOW. This information can be used to drive a sound
processor or a DC volume control to attenuate the input signal and so limit the level of
distortion. The output level of pin CLIP is independent of the number of channels that are
being clipped. The clip detection circuit is disabled in a short-circuit condition, so if a fault
condition occurs at the outputs, pin CLIP will remain at a HIGH level. The clip detection
waveforms are illustrated in Figure 5.
Product data sheetRev. 06 — 15 October 20076 of 21
NXP Semiconductors
V
TDA8566
2 × 40 W/2 Ω stereo BTL car radio power amplifier
V
O
(V)
0
CLIP
(V)
0
t (s)
mgu357
Fig 5. Clip detection waveforms
7.3 Short-circuit diagnostic (pin DIAG)
When a short-circuit occurs at one or more outputs to ground or to the supply voltage, the
output stages are switched off until the short-circuit is removed and the device is switched
on again (with a delay of approximately 20 ms after the removal of the short-circuit).
During this short-circuit condition, pin DIAG is continuously LOW.
When a short-circuit occurs across the load of one or both channels, the output stages are
switched off for approximately 20 ms. After that time the load condition is checked during
approximately 50 µs to see whether the short-circuit is still present. Due to this duty cycle
of 50 µs/20 ms the average current consumption during the short-circuit condition is very
low (approximately 40 mA). During this condition, pin DIAG is LOW for 20 ms and HIGH
for 50 µs; see Figure 6. The power dissipation in any short-circuit condition is very low.
current
in
output
stage
t (s)
t (s)
mgu360
V
DIAG
(V)
short-circuit over the load
20 ms
50 µs
Fig 6. Short-circuit diagnostic timing diagram
7.4 Temperature pre-warning (pin DIAG)
When the virtual junction temperature (Tvj) reaches 145 °C, pin DIAG will become
continuously LOW.
7.5 Open-collector diagnostic outputs
Pins DIAG and CLIP are open-collector outputs, therefore more devices can be tied
together. Pins DIAG and CLIP can also be tied together. An external pull-up resistor is
required.