TMPA420DS - Tai-1 Microelectronics Corp.

Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

15W/Ch STEREO CLASS-D AUDIO POWER AMPLIFIER

GENERAL DESCRIPTION

The TMPA420DS is a Bridge-Tied-Load (BTL) output Class-D

audio power amplifier for driving speakers with high power

efficiency. It is able to drive 4Ω, 6Ω, 8Ω or 16Ω speakers.

The output power can be up to 15W per channel. No external

heat-sink is necessary.

The gain of the amplifier is defined by either gain0/gain1

gain control or by input resistance. Thermal protection and

short-circuit protection are integrated for safety purpose.

The internal de-pop circuitry eliminates pop noise at

power-up & shutdown operations.

APPLICATIONS

LCD Monitors, TVs, DVD Players and Powered Speakers

PACKAGE

QFN48 available

FEATURES

♦ 15W/Ch Stereo Class-D Output

♦ Power efficiency is up to 82%

♦ Convenient gain control

♦ Time delay for de-pop control

♦ Thermal Protection

♦ Output Pin Short-Circuit Protection

♦ Low Quiescent Current (10mA Typical at 12V)

♦ Low Current in Shutdown Mode (<1µA Typical)

♦ Separate VCC & PVCC

♦ Regulated 5-V Supply Output

For best performance, please refer to

http://www.taimec.com.tw/English/EVM.htm

http://www.class-d.com.tw/English/EVM.htm

for PCB layout.

REFERENCE CIRCUIT

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

PVCCL

LOUTN

PGNDL

LOUTP

PVCCL

LOUTP

PVCCR

ROUTN

PGNDR

ROUTP

PVCCR

ROUTP

NC

NC NC

NC

（Please email david@taimec.com.tw for complete datasheet.）

Tai-1 Microelectronics reserves the right to make corrections, modifications, enhancements, improvements, and other

changes to its products and services at any time and to discontinue any product or service without notice. Customers are

responsible for their products and applications using Tai-1 Microelectronics components.

Note that the external components or PCB layout should be designed not to generate abnormal

voltages to the chip to prevent from latch up which may cause damage to the device.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

Typical Application

S1switch

C13 1uF(6.3V)

C24

0.1uF(16V)

C4 1uF(6.3v) C5 1uF(6.3v)

+

C16

10uF(16V)

C25

0.1uF(16v)

R9

10k

SD

1

RINN

2

RINP

3

HFVDDR

4

LINP

5

NC

12

LINN

6

NC

11

HFVDDL

7

AGND

8

GAINO

9

GAIN1

10

NC

13

PVCCL

14

PVCCL

15

LOUTN

16

LOUTN

17

NC

24

PGNDL

18

PVCCL

23

PGNDL

19

LOUTP

20

LOUTP

21

PVCCL

22

NC 37

PVCCR 38

PVCCR 39

ROUTP 40

ROUTP 41

NC 48

PGNDR 42

PVCCR 47

PGNDR 43

ROUTN 44

ROUTN 45

PVCCR 46

NC 25

AGND 26

HFRC 27

AVDD 28

VDDZ 29

NC 36

AGND 30

NC 35

NC 31

NC 32

AVCC 33

NC 34

U1

420DS

PVCC

C11 1uF(6.3v) C6 1uF(6.3v)

C3 1uF(6.3v)

C12 1uF(6.3v)

PVCC

C26

0.1uF(16v)

PVCC

C14 1uF(6.3V)

C22

0.1uF(16V)

PVCC

C23

0.1uF(16V)

PVCC

SD

RINP

LINP

J2 SW SPST

J3 SW SPST

R12

100

PVCC

L8

33uH

C8

1uF(16V)

L7

33uH

C7

1uF(16V)

LOUT+LOUT-

L5

33uH

C1

1uF(16V)

L6

33uH

C2

1uF(16V)

ROUT- ROUT+

R5 22k

C9

0.47nF(6.3v)

C10

0.47nF(6.3v)

R6 22k

R7 22k

R8 22k R10 120k

R11 120k

AVDD

J1

PHONEJACK STEREO

J4

VR R1 0

C18

1000uF(25V)

C19

1000uF(25V)

R2 330

R3 330

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

TERMINAL FUNCTIONS

TERMINAL

NAME PIN NO I/O

DESCRIPTION

AGND 8,26,30 － Analog ground

AVCC 33 － High-voltage power supply (8V to 15V)

AVDD 28 I 5-V voltage

HFVDDR 4 O 2.5-V Reference for convenience of single-ended inputs

HFVDDL 7 O 2.5-V Reference for convenience of single-ended inputs

HFRC 27 O Power up delay

LINN 6 I Negative differential input for left channel

LINP 5 I Positive differential input for left channel

LOUTN 16,17 O Class-D negative output for left channel

LOUTP 20,21 O Class-D positive output for left channel

PGNDL 18,19 － Power ground for left channel

PGNDR 42,43 － Power ground for right channel

PVCCL 14,15,22,23

－ Power supply for left channel(8V to 15V)

PVCCR 38,39,46,47

－ Power supply for right channel(8V to 15V)

RINP 3 I Positive differential input for right channel

RINN 2 I Negative differential input for right channel

ROUTN 44,45 O Class-D negative output for right channel

ROUTP 40,41 O Class-D positive output for right channel

SD 1 I Shutdown (Low valid)

GAIN0 9 I Gain0 control

GAIN1 10 I Gain1 control

VDDZ 29 O 5-V Regulated output (25mA output)

NC 11,12,13,24,

25,31,32,34,

35, 36,37,48

－ No connection

ABSOLUTE MAXIMUM RATINGS

Over operating free-air temperature range unless otherwise noted(1)

In normal mode -0.3V to 17V V

Supply voltage, PVCCR, PVCCL, AvCC (Iload=0) In shutdown mode -0.3V to 17V V

Input voltage, SD -0.3V to AVCC+0.3V V

Input voltage, Gain0, Gain1, LINN, LINP, RINN, RINP -0.3V to 5V V

Continuous total power dissipation See package dissipation ratings

Operating free-air temperature, TA -20 to 85 。

C

Operating junction temperature, TJ -20 to 150 。

C

Storage temperature, Tstg -40 to 150 。

C

(1) Stresses beyond those listed under”absolute maximum ratings” may cause permanent damage to the device. These are stress ratings

only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating

conditions “is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

RECOMMENDED OPERATING CONDITIONS

MIN MAX UNIT

Supply voltage, VCC PVCCR, PVCCL, AvCC 8 15 V

High-level input voltage, VIH SD , Gain0, Gain1 2.0 V

Low-level input voltage, VIL SD , Gain0, Gain1 0.8 V

VCC=15V, SD =15V 100

High-level input current, IIH VCC=15V, Gain0=Gain1=5V 5 uA

VCC=15V, SD =0V 0.5

Low-level input current, IIL VCC=15V, Gain0=Gain1=0V 0.5 uA

Operating free-air temperature, TA -20 85 。

C

PACKAGE DISSIPATION RATINGS

PACKAGE DERATING

FACTOR TA

≤

25。

C

POWER RATING TA = 70。

C

POWER RATING TA = 85。

C

POWER RATING

QFN48(FD) 33 mW/。

C 4.125W 2.64W 2.15W

DC CHARACTERISTICS

TA=25。

C, VCC=15V, RL=8Ω speaker (unless otherwise noted)

PARAMETER TEST CONDITIONS

MIN

TYP MAX

UNIT

│VOS│ Output offset voltage LINN LINP RINN RINP AC

grounded 30 mV

VDD/AVDD 5-V Regulated output IO=0 to25mA, SD =High,

VCC=8V to 15V 4.5 5.0 5.5 V

fOSC Oscillator frequency PVCC= VCC=8-15V 250 350 kHz

HFVDDR/HFVDDL Half VDD reference output No load 0.5×

AVDD

SD =High, VCC= 12V 10 20

ICC Quiescent current (no load) SD =High, VCC= 15V 16 30 mA

ICC(SD) Supply current in shutdown mode SD =0.8V, VCC= 9V~15V 1 uA

High side 600

Low side 500

rds(on) Drain-source on-state resistance

for all

outputs

VCC=15V

IO=1A,

Total 1100 mΩ

Gain0=High, Gain1= High

34

Gain0=Low, Gain1=High

28

Gain0=High, Gain1= Low

22

Voltage Gain at Vcc=15V

Gain0=Low, Gain1= Low

18

dB

Gain0=High, Gain1= High

32

Gain0=Low, Gain1=High

26

Gain0=High, Gain1= Low

20

Voltage Gain at Vcc=12V

Gain0=Low, Gain1= Low

16

Gain0=High, Gain1= High

30

Gain0=Low, Gain1=High

25

Gain0=High, Gain1= Low

19

Gain

Voltage Gain at Vcc=9V

Gain0=Low, Gain1= Low

14

dB

Gain0=High, Gain1= High

15

Gain0=Low, Gain1=High

30

Gain0=High, Gain1= Low

60

Zi Input resistance of

RINN/RINP/LINN/LINP Gain0=Low, Gain1= Low

100

kΩ

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

AC CHARACTERISTICS

TA=25。

C, VCC=15V, RL=8Ω speaker (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN

TYP MAX

UNIT

15V 12.5

12V 10

RL=4Ω 9V 6.22

W

15V 15

12V 9.3

RL=6Ω 9V 5.34

W

15V 12.7

12V 8

RL=8Ω 9V 4.58

W

15V 7.65

12V 4.8

*PO(max)

Maximum continuous output power

(r.m.s) at 1kHz,

(Limited by thermal condition)

RL=16Ω

9V 2.73

W

Vn Output noise -70 dBV

SNR Signal-to-noise ratio Maximum output at THD+N＜0.5％,

f=1kHz 85 dB

Crosstalk

Crosstalk between outputs Gain0=Gain1=high, VCC=12V, PO

=1W

RL=8Ω -60 dB

Thermal trip point 145 。

C

Thermal hysteresis 25 。C

*Important notice：More copper area and vias are required for high output power especially

when the output power is higher than 7W×2.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

DETAILED DESCRIPTION

Efficiency

The output transistors of a class D amplifier act as switches. The power loss is mainly due to

the turn on resistance of the output transistors when driving current to the load. As the turn on

resistance is so small that the power loss is small and the power efficiency is high. With 8 ohm

load the power efficiency can be better than 80%.

PCB layout for power dissipation

No heat sink is necessary for power dissipation. However the PCB layout should be well

designed to dissipate heat for high output power. With 80% power efficiency the generated

heat when driving 15 watts to the 8 ohm load is about 3.75 watts. The heat can be carried out

through the thermal pad of the device to the PCB. To ensure proper dissipation of heat the

PCB has to have heat path from the bottom of the device which is soldered to the PCB. The

area of the metal on the PCB for heat dissipation should be big enough. It is suggested that

both sides of the PCB are used for power dissipation.

Shutdown

The shutdown mode reduces power consumption. A LOW at shutdown pin forces the device in

shutdown mode and a HIGH forces the device in normal operating mode. Shutdown mode is

useful for power saving when not in use. This function is useful when other devices like

earphone amplifier on the same PCB are used but class D amplifier is not necessary.

Internal circuit for shutdown is shown below.

HFRC（pop-less）

HFRC provides a way of soft start up delay. A half_Vcc voltage detector is integrated to detect

a RC charge up. The resistor of 320k ohms of the RC circuit is also integrated in the chip but

the capacitor is externally hooked up. For C=1uF the half_Vcc delay is

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

1-e-t/RC=0.5

or e-t/RC=0.5

that is

t = - RC In（0.5）= （320k × 1u）（ 0.693） = 0.22 seconds

Differential input VS single ended input

Differential input offers better noise immunity over single ended input. A differential input

amplifier suppresses common noise and amplifies the difference voltage at the inputs. For

single ended applications just tie the negative input end of the balanced input structure to

ground. If external input resistors are used, the negative input has to be grounded with a

series resistor of the same value as the positive input to reduce common noise.

Voltage gain

The voltage gain can be set through gain0/gain1 control or by external input resistors

connecting to input pins. If external resistors are used they should be well matched. Well

matched resistors are also required even for single ended input configuration for low noise.

Suppose the external input resistors Rext are used then the voltage gain is roughly

Av=750k ohms / (Rext+15k ohms) for gain0=gain1=High

Where 15k ohms is the internal resistance of the input pins. For other gain0/gain1 states

please refer to DC CHARACTERISTICS for different input resistance.

Input filter

AC coupling capacitors are required to block the DC voltage from the device. They also define

the –3db frequency at the low frequency side.

The –3db frequency of the low frequency side is

f-3db = 1/ (2πR C)

where C is the AC coupling capacitance and R is the total resistance in series with C.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

Note that R=Zin(internal resistance) + Rext(external resistance)

Also note that the input resistance of RINN/RINP/LINN/LINP is 15K ohms at

Gain0=Gain1=high. Please refer to DC CHARACTERISTICS for detail.

In the following diagram Rext=22k ohms, Zin=15k ohms and C=C1=0.47uF. Thus the –3db

frequency at the low frequency side is about 9Hz.

C1

0.47uF

R22k C1

0.47uF

Zin 15k

R22k

Zin 15k

Class-D amplifier

Rinp

Rinn

C2

0.47nF

C1

0.47uF

R22k C1

0.47uF

Zin 15k

R22k

Zin 15k

Linp

Linn

C2

0.47nF

right channel

left channel

A bypass capacitor placed in between the positive signal path and negative signal path is to

attenuate the high frequencies. It defines the –3bd frequency at the high frequency side. The

input filter becomes a band pass filter.

The –3db frequency of the high frequency side is

f–3db=1/(2πRC)

where C is the bypass capacitance and R is the total resistance in parallel with C.

In this example Rext=22k ohms, Zin=15k ohms and C=C2=0.47nF. Thus the –3db frequency

at the high frequency side is about 19kHz.

Output filter

Ferrite bead filter can be used for EMI purpose. The ferrite filter reduces EMI around 1 MHz

and higher（FCC and CE only test radiated emissions greater than 30 MHz）. When selecting a

ferrite bead, choose one with high impedance at high frequencies, but low impedance at low

frequencies.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

Use an LC output filter if there are low frequency（＜1 MHz）EMI sensitive circuits and/or there

are long wires from the amplifier to the speaker. EMI is also affected by PCB layout and the

placement of the surrounding components.

The suggested LC values for different speaker impendence are showed in following figures for

reference.

Typical LC Output Filter (1)

0.1μF

Vo+

Vo-

33

μ

H

33

μ

H

0.47μF

Typical LC Output Filter (2)

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

EARPHONE USE

Class-D output can be used to drive earphone. However to avoid high power to overdrive

earphone and to prevent human ear to accidentally be hurt, a resistor has to be put in series

with the earphone speaker. Typically a resistor of 330 ohms is adequate for this purpose.

Since stereo earphone can not have BTL configuration, one end of BTL signals can be used

as SE (single-ended) output.

Over temperature protection

A temperature sensor is built in the device to detect the temperature inside the device. When

a high temperature around 145oC and above is detected the switching output signals are

disabled to protect the device from over temperature. Automatic recovery circuit enables the

device to come back to normal operation when the internal temperature of the device is below

around 120 oC.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

Over temperature protection

A temperature sensor is built in the device to detect the temperature inside the device. When

a high temperature around 145oC and above is detected the switching output signals are

disabled to protect the device from over temperature. Automatic recovery circuit enables the

device to come back to normal operation when the internal temperature of the device is below

around 120oC.

Over current protection

A current detection circuit is built in the device to detect the switching current of the output

stages of the device. It disables the device when a pulse current beyond 8 amps is detected. It

protects the device when there is an accident short between outputs or between output and

ground pins. It also protects the device when an abnormal low impedance is tied to the output.

High current beyond the specification may potentially causes electron migration and

permanently damage the device. Shutdown or power down is necessary to resolve the

protection situation. There is no automatic recovery from over current protection.

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

Physical Dimensions ( IN MILLIMETERS)

QFN48

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Preliminary TMPA420DS

tai'mec

www.taimec.com.tw / www.class-d.com.tw Rev.3.0 August 15, 2007

IMPORTANT NOTICE

Tai-1 Microelectronics Corp. reserves the right to make changes to its products and services and to

discontinue any product or service without notice. Customers should obtain the latest relevant information for

reference. Testing and quality control techniques are used to screen the parameters. Testing of all

parameters of each product is not necessarily performed.

Tai-1 Microelectronics Corp. assumes no liability for applications assistance or customer product design. To

minimize the risks associated with customer products and applications, customers should provide adequate

design and operating safeguards.

Reproduction of information in data sheets or related documentation is permissible only if reproduction is

without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Tai-1

Microelectronics Corp. is not responsible or liable for such altered documentation.

Resale of Tai-1 Microelectronics Corp. products or services with statements different from the parameters

stated by Tai-1 Microelectronics Corp. for that product or service voids all express and any implied warranties.

Tai-1 Microelectronics Corp. is not responsible or liable for any such statements.

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