Philips TDA8945S Datasheet

TDA8945S

15 W mono Bridge Tied Load (BTL) audio ampliﬁer

Rev. 02 — 7 April 2000 Product speciﬁcation

1. General description

The TDA8945S is a single-channel audio power ampliﬁer with an output power of 15 W at an 8 Ω load and an 18 V supply. The circuit contains a Bridge Tied Load (BTL) ampliﬁer with anall-NPN output stage and standby/mute logic. The TDA8945S comes in a 9-lead single in-line (SIL) power package. The TDA8945S is printed-circuit board (PCB) compatible with all other types in the TDA894x family. One PCB footprint accommodates both the mono and the stereo products.

2. Features

■ Few external components

■ Fixed gain

■ Standby and mute mode

■ No on/off switching plops

■ Low standby current

■ High supply voltage ripple rejection

■ Outputs short-circuit protected to ground, supply and across the load

■ Thermally protected

■ Printed-circuit board compatible.

3. Applications

■ Mains fed applications (e.g. TV sound)

■ PC audio

■ Portable audio.

4. Quick reference data

Table 1: Quick reference data

Symbol Parameter Conditions Min Typ Max Unit

stb

supply voltage 6 18 25 V quiescent supply current VCC=18V; RL= ∞ - 1828mA standby supply current - - 10 µA

Philips Semiconductors

TDA8945S

15 W mono BTL audio ampliﬁer

Table 1: Quick reference data

Symbol Parameter Conditions Min Typ Max Unit

THD total harmonic distortion P G

SVRR supply voltage ripple

5. Ordering information

Table 2: Ordering information

Type number Package

TDA8945S SIL9P plastic single in-line power package; 9 leads SOT131-2

6. Block diagram

dth

…continued

output power THD = 10%; RL=8Ω;

=18V

= 1 W - 0.03 0.1 %

13 15 - W

voltage gain 31 32 33 dB

50 65 - dB

rejection

Name Description Version

IN− IN+

MODE

SVR

Fig 1. Block diagram.

TDA8945S

5 4

STANDBY/

MUTE LOGIC

kΩ

GND

SHORT CIRCUIT

AND

TEMPERATURE

PROTECTION

MBK938

OUT−

OUT+

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7. Pinning information

7.1 Pinning

TDA8945S

15 W mono BTL audio ampliﬁer

handbook, halfpage

OUT−

OUT+

IN+ IN−

SVR

MODE

GND

n.c.

1 2 3 4 5

TDA8945S

6 7 8 9

MBK937

Fig 2. Pin conﬁguration.

7.2 Pin description

Table 3: Pin description

Symbol Pin Description

OUT− 1 negative loudspeaker terminal V

OUT+ 3 positive loudspeaker terminal IN+ 4 positive input IN− 5 negative input SVR 6 half supply voltage decoupling (ripple rejection) MODE 7 mode selection input (standby, mute, operating) GND 8 ground n.c. 9 not connected

2 supply voltage

8. Functional description

The TDA8945S is a mono BTL audio power ampliﬁer capable of delivering 15 W output power to an 8 Ω load at THD = 10%, using an 18 V power supply and an external heatsink. The voltage gain is ﬁxed at 32 dB.

With the three-level MODE input the device can be switched from ‘standby’ to ‘mute’ and to ‘operating’ mode.

The TDA8945S outputs are protected by an internal thermal shutdown protection mechanism and a short-circuit protection.

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8.1 Input conﬁguration

The TDA8945S inputs can be driven symmetrical (ﬂoating) as well as asymmetrical. In the asymmetrical mode one input pin is connected via a capacitor to the signal ground which should be as close as possible to the SVR (electrolytic) capacitor ground. Note that the DC level of the input pins is half of the supply voltage VCC, so coupling capacitors for both pins are necessary.

The input cut-off frequency is:

TDA8945S

15 W mono BTL audio ampliﬁer

i cut off–()

For Ri=45kΩ and Ci= 220 nF:

i cut off–()

As shown in Equation 1 and 2, large capacitor values for the inputs are not necessary; so the switch-on delay during charging of the input capacitors, can be minimized. This results in a good low frequency response and good switch-on behaviour.

Remark: To prevent HF oscillations do not leavethe inputs open, connect a capacitor of at least 1.5 nF across the input pins close to the device.

---------------------------- -

2π RiCi×()

---------------------------------------------------------------- -

2π 45 103× 220× 109–×()

16 Hz==

8.2 Power ampliﬁer

The power ampliﬁer is a Bridge Tied Load (BTL) ampliﬁer with an all-NPN output stage, capable of delivering a peak output current of 2 A.

The BTL principle offers the following advantages:

Lower peak value of the supply current

•

The ripple frequency on the supply voltage is twice the signal frequency

•

No expensive DC-blocking capacitor

•

Good low frequency performance.

•

(1)

(2)

8.2.1 Output power measurement

The output power as a function of the supply voltage is measured on the output pins at THD = 10%; see Figure 8. The maximum output power is limited by the maximum supply voltage of 18 V and the maximum availableoutput current: 2 A repetitive peak current.

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8.2.2 Headroom

Typical CD music requires at least 12 dB (factor 15.85) dynamic headroom – compared to the average power output – for transferring the loudest parts without distortion. At VCC=18V, RL=8Ω and Po= 10 W at THD = 0.1% (see Figure 6), the Average Listening Level (ALL) – music power – without any distortion yields:

The power dissipation can be derived from Figure 11 on page 10 for 0 dB respectively 12 dB headroom.

Table 4: Power rating as function of headroom

Headroom Power output (THD = 0.1%) Power dissipation (P)

0dB P 12 dB P

For the average listening level a power dissipation of 4 W can be used for a heatsink calculation.

= 10 W/15.85 = 631 mW.

o(ALL)

15 W mono BTL audio ampliﬁer

=10W 8.5W

= 631 mW 4 W

o(ALL)

TDA8945S

8.3 Mode selection

The TDA8945S has three functional modes, which can be selected by applying the proper DC voltage to pin MODE. See Figure 4 and 5 for the respective DC levels, which depend on the supply voltage level. The MODE pin can be driven by a 3-state logic output stage: e.g. a microcontroller with additional components for DC-level shifting.

Standby — In this mode the current consumption is very low and the outputs are ﬂoating. The device is in standby mode when (VCC− 0.5 V) < V the MODE pin is left ﬂoating (high impedance). The power consumption of the TDA8945S will be reduced to <0.18 mW.

Mute — In this mode the ampliﬁer is DC-biased but not operational (no audio output);

the DC level of the input and output pins remain on half the supply voltage. This

allows the input coupling and Supply Voltage Ripple Rejection (SVRR) capacitors to be charged to avoid pop-noise. The device is in mute mode when 3V<V

Operating — In this mode the ampliﬁer is operating normally. The operating mode is activated at V

8.3.1 Switch-on and switch-off

To avoid audible plops during supply voltage switch-on or switch-off, the device is set to standby mode before the supply voltage is applied (switch-on) or removed (switch-off).

<(VCC− 1.5 V).

MODE

< 0.5 V.

MODE<VCC

, or when

The switch-on and switch-off time can be inﬂuenced by an RC-circuit on the MODE pin. Rapid on/off switching of the device or the MODE pin may cause ‘click- and pop-noise’. This can be prevented by proper timing of the RC-circuit on the MODE pin.

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8.4 Supply Voltage Ripple Rejection (SVRR)

The SVRR is measured with an electrolytic capacitor of 10 µF on pin SVR at a bandwidth of 10 Hz to 80 kHz. Figure 12 on page 11 illustrates the SVRR as function of the frequency.A larger capacitor value on the SVR pin improvesthe ripple rejection behaviour at the lower frequencies.

8.5 Built-in protection circuits

The TDA8945S contains two types of protection circuits, i.e. short-circuit and thermal shutdown.

8.5.1 Short-circuit protection

Short-circuit to ground or supply line — This is detected by a so-called ‘missing

current’ detection circuit which measures the current in the positive supply line and the current in the ground line. A difference between both currents larger than 0.7 A, switches the power stage to standby mode (high impedance).

Short-circuit across the load — This is detected by an absolute-current measurement. An absolute-current larger than 3 A, switches the power stage to standby mode (high impedance).

TDA8945S

15 W mono BTL audio ampliﬁer

8.5.2 Thermal shutdown protection

9. Limiting values

The junction temperature is measured by a temperature sensor; at a junction temperature of approximately 150 °C this detection circuit switches the power stage to standby mode (high impedance).

Table 5: Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol Parameter Conditions Min Max Unit

ORM

stg

case

tot

CC(sc)

supply voltage no signal −0.3 +25 V

operating −0.3 +18 V input voltage −0.3 VCC+ 0.3 V repetitive peak output current - 2 A storage temperature non-operating −55 +150 °C operating case temperature −40 +70 °C total power dissipation - 14 W supply voltage to guarantee

short-circuit protection

-18V

10. Thermal characteristics

Table 6: Thermal characteristics

Symbol Parameter Conditions Value Unit

th(j-mb)

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Product speciﬁcation Rev. 02 — 7 April 2000 6 of 21

thermal resistance from junction to mounting base in free air 9 K/W

Philips Semiconductors

TDA8945S

15 W mono BTL audio ampliﬁer

11. Static characteristics

Table 7: Static characteristics

VCC=18V; T

Symbol Parameter Conditions Min Typ Max Unit

stb

[3]

∆V

OUT

MODE

[1] With a load connected at the outputs the quiescent current will increase, the maximum of this increase being equal to the differential

output voltage offset (∆V [2] The DC output voltage with respect to ground is approximately 0.5VCC. [3] ∆V

OUT

=25°C; RL=8Ω; V

amb

supply voltage operating 6 18 25 V quiescent supply current RL= ∞ standby supply current V DC output voltage differential output voltage offset - - 200 mV mode selection input voltage operating mode 0 - 0.5 V

mode selection input current 0 < V

= | V

OUT+

− V

=0V; Vi= 0 V; measured in test circuit Figure 13; unless otherwise speciﬁed.

MODE

) divided by the load resistance (RL).

OUT

OUT−

[1]

- 1828mA

MODE=VCC

--10µA

[2]

-9-V

mute mode 3 - V standby mode V

MODE<VCC

− 0.5 - V

--20µA

− 1.5 V

CC CC

handbook, halfpage

(mA)

0481216

MGU052

VCC (V)

Fig 3. Quiescent supply current as function of supply

voltage.

MODE

MGU053

(V)

handbook, halfpage

(mA)

0481216

VCC = 18 V

12 V

Fig 4. Quiescent supply current as function of mode

voltage.

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