T E C H N I C A L I N F O R M A T I O N

Absolute Maximum Ratings

SYMBOL

PARAMETER

Value

UNITS

Supply Voltage (Vspos & Vsneg)

+/-50

Positive 5 V Bias Supply

VGG

Internally generated voltage

STORE

Storage Temperature Range

-40 to 150

ºC

Operating Free-air Temperature Range

-20 to +80

ºC

Notes:

Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
Damage will occur to the device if VN10 is not supplied or falls below the recommended
operating voltage when V

is within its recommended operating range.

Operating Conditions

SYMBOL

PARAMETER

MIN.

TYP.

MAX.

UNITS

Supply Voltage (Vspos & Vsneg)

+/- 25

+/- 35

+/- 45

Positive 5 V Bias Supply

4.5

5.5

VGG

Internally Generated Voltage

Note: Recommended Operating Conditions indicate conditions for which the device is functional. See
Electrical Characteristics for guaranteed specific performance limits.

Electrical Characteristics

= 25

C. See Notes 1 & 2 for Operating Conditions and Test/Application Circuit Setup.

SYMBOL

PARAMETER

MIN.

TYP.

MAX.

UNITS

Quiescent Current

+35V

(no load)

-35V

+5V

VN12

mA
mA
mA
mA

Source Current @ P

OUT

= 100W, R

= 4

SPOS

= +35V

@ 10% THD+N

SNEG

= -35V

A
A

Source Current for 5V Bias Supply @ P

OUT

= 100W, R

= 4

IVGG

Source Current for VGG Supply @ P

OUT

= 100W, R

= 4

Under Voltage (Vspos & Vsneg)

Over Voltage (Vspos & Vsneg)

High-level Input Voltage (MUTE & SLEEP)

3.5

Low-level Input Voltage (MUTE & SLEEP)

MUTE

Mute Supply Current

+35V

(no load)

-35V

+5V

VGG

mA
mA
mA
mA

High-level Output Voltage (HMUTE/SDA, OVERLOAD/SCL &
PSMUTE)

3.5

Low-level Output Voltage (HMUTE/SDA, OVERLOAD/SCL &
PSMUTE)

TOC

Over Current Sense Voltage Threshold

1.2

Gain Ratio V

OUT

, R

= 0

V/V

Voffset

Offset Voltage, no load, MUTE = Logic low

T E C H N I C A L I N F O R M A T I O N

Minimum and maximum limits are guaranteed but may not be 100% tested.

Performance Characteristics Single Ended

Unless otherwise specified, f = 1kHz, Measurement Bandwidth = 22kHz. T

= 25

See Notes 1 & 2 for Operating Conditions and Test/Application Circuit Setup.

Minimum and maximum limits are guaranteed but may not be 100% tested.

Notes:

VP1=VP2=+35V, VN1=VN2=-35V, V5 = +5V, VGG = +11V referenced to PGND

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNITS

OUT

Output Power
(continuous RMS/Channel)

THD+N = 0.1%, R

= 8

= 4

THD+N = 10%, R

= 8

= 4

100

125

W
W
W
W

THD + N

Total Harmonic Distortion Plus
Noise

OUT

= 4W/Channel, R

= 4

.02

IHF-IM

IHF Intermodulation Distortion

19kHz, 20kHz, 1:1 (IHF), R

= 4

OUT

= 1W/Channel

0.08

SNR

Signal-to-Noise Ratio

A Weighted, R

= 4

OUT

= 100W/Channel

110

Channel Separation

0dBr = __W, R

= 4

, f = 1kHz

PSRR

Power Supply Rejection Ratio

Input Referenced, 30kHz Bandwidth

Power Efficiency

OUT

= 90W/Channel, R

= 8

NOUT

Output Noise Voltage

A Weighted, no signal, input shorted,
DC offset nulled to zero

150

T E C H N I C A L I N F O R M A T I O N

Pin Description

Function

Description

1,13

VB2,VB1

Bootstrapped voltages supply drive to gates of high-side FET's

VGG

Regulated output of onboard switching regulator

PGND

Power ground

4,12

VP2,VP1

Positive power supply connections

SW12V

Switching node

6,11

VS2,VS1

Source voltage for high side FET's

7,10

OUT2,OUT1

Power FET outputs

8,9

VN2,VN1

Negative power supply connections

SWFB

Feedback for onboard regulator

SLEEP

When set to logic high, both amplifiers are muted and in low power (idle)
mode. When low (grounded), both amplifiers are fully operational. If left
floating, the device stays in the mute mode. Ground if not used.

PSMUTE

A logic high output indicates the amplifiers are muted

OVRLD/SCL

Dual function pin:
OVRLD A logic high output indicates that the level of the input signal has
overloaded the amplifiers, signifying increased distortion
SCL When tied to V5 through a pull-up resistor, this pin becomes the serial
clock line of the serial control bus

HMUTE/SDA

Dual function pin:
HMUTE A logic high output indicates that the output stages of both
amplifiers are shut off and muted.
SDA When OVRLD/SCL is tied to V5 through a pull up resistor, this pin
becomes the serial data line of the serial control bus

MUTE

When set to logic high, both amplifiers are muted. When set to logic low or
grounded both amplifiers are fully operational. Ground if not used.

MIS/ADDR

Dual function pin:
MIS When control/status of the device is via analog pins, the voltage level
ion this pint sets the Mute-in silence threshold
ADDR When OVRLD/SCL is tied to V5 through a pull up resistor, the voltage
on this pin selects the chip address of the device for the serial control bus

5V power supply

AGND

Analog Ground

23,24

INP1,INP2

Inputs for channels 1 and 2

25,26

AUXOUT1,AUXOUT2

Auxiliary outputs that provide a low impedance, buffered audio output
where the signal level is set by the volume control

V2BG

Bandgap reference

DCVOL

When control/status of the device is via analog pins, the voltage level on this
pin sets the output signal volume

29,31

FDBKN1,FDBKN2

Feedback for channels 1 and 2

30,32

GNDKELVIN1
GNDKELVIN2

Kelvin connection to speaker ground channels 1 and 2

T E C H N I C A L I N F O R M A T I O N

Test/Application Circuit

TA2021-100

MUTE

INP1

AGND

VS1

VN1

OUT1

SLEEP

FDBKN1

PSMUTE

OVRLD/SCL

VP1

GNDKELVIN1

MIS/ADDR 19

V2BG

Note - Heavy Lines Indicate High-Current Paths

SW-FB

SW12

VGG

VB1

INP2

HMUTE/SDA

+5V

AUXOUT2

AUXOUT1

Positive Supply Star
N d

Negative Supply Star
N d

Positive Supply Star

OUT2

VB2

GNDKELVIN2

FDBKN2

VP2

VN2

VS2

Negative Supply Star
N d

PGND

VB1 VB2

Power Supply Ground Star
N d

DCVOL

T E C H N I C A L I N F O R M A T I O N

Modes of Operation

The TA2021-100 has two modes of operation: Mode 1, where control/status of the amplifier is
by signals on analog pins of the TA2021-100, and Mode 2, where control/status of the amplifier
is by registers accessed through a digital serial control bus. When OVRLD/SCL is tied to V5
through a 5 K

resistor and the TA2021-100 senses this during power-up it will go into Mode 2

operation. Otherwise the TA2021-100 will use Mode 1 operation. The operating description in
this section explains operation of the TA2021-100 in Mode 1. Mode 2 operation is described in
the next section.

TA2021-100 Basic Amplifier Operation

The audio input signal is fed to the processor internal to the TA2021-100, where a modulation
pattern is generated. This pattern is spread spectrum and varies between approximately
200kHz and 1.5MHz. Complementary copies of the switching pattern are level-shifted by
MOSFET drivers which drive the gates of internal power MOSFETs that are connected as a half
bridge. The output of the half bridge is a power-amplified version of the switching pattern
that switches between VP and VN. This signal is then low-pass filtered to obtain amplified
audio.

The processor portion of the TA2021-100 is operated from a 5-volt supply (between V5 and
GND). In the generation of the complementary modulation pattern for the output MOSFETs,
the processor inserts a "break-before-make" dead time between when it turns one transistor
off and it turns the other one on in order to minimize shoot-through currents in the MOSFETs.
Feedback information from the output of the half-bridge is supplied to the processor via
FDBKN1. Additional feedback information to account for ground bounce is supplied via
GNDKELVIN1.

The MOSFET drivers in the TA2021-100 are operated from voltages obtained from VGG for the
low-side driver, and VB1 for the high-side driver. VGG must be a stable 12V above VN. The
TA2021-100 provides switching regulator circuitry to supply VGG and VB1.

Over- and Under-Voltage Protection

The TA2021-100 senses the power rails for over- and under-voltage conditions. The over- and
under-voltage limits are Vo and Vu respectively as specified in the Electrical Characteristics
table. If the supply voltage exceeds Vo or drops below Vu, the TA2021-100 shuts off the
output stages of the amplifiers and asserts a logic level high on HMUTE/SDA. The removal of
the over-voltage or under-voltage condition returns the TA2021-100 to normal operation and
returns HMUTE/SDA to a logic level low. Please note that the limits specified in the Electrical
Characteristics table are at 25

C and these limits may change over temperature.

Over-current Protection

The TA2021-100 has over-current protection circuitry to protect itself and the output transistors
from short-circuit conditions. The TA2021-100 uses the voltage across a resistor that is in series
with each output MOSFET to detect an over-current condition.

T E C H N I C A L I N F O R M A T I O N

When the voltage drop becomes greater than V

OC-LIMIT

(approximately 0.7V) the TA2021-100 will

try to limit the current by internally decreasing the gain of the input stage of the TA2021-100.
If the voltage drop continues to increase to greater than V

OC-SD

(approximately 1.2V) the TA2021-

100 will shut off the output stages of its amplifiers and supply a logic level high on
HMUTE/SDA. The occurrence of an over-current condition is latched in the TA2021-100 and can
be cleared by toggling the MUTE input or cycling power.

Mute

When a logic high signal is supplied to MUTE, both amplifier channels are muted (both high-
and low-side transistors are turned off) and a logic level high is output on the HMUTE/SDA pin.
When a logic level low is supplied to MUTE, both amplifiers are fully operational and a logic
level low is supplied on HMUTE/SDA. There is a delay of approximately 200 milliseconds
between the de-assertion of MUTE and the un-muting of the TA2021-100.

Mute-in-silence

The TA2021-100 will automatically mute both channels when the sum of the audio signal
supplied to both of its inputs is below a preset level for approximately 340 seconds. The preset
audio level is determined by the voltage on the MIS/ADDR pin according to the following table
(The MIS/ADDR pin also determines the input-limit level, as described in the next section):

MIS/ADDR Pin Voltage

(Fraction of V5)

MIS Level

Input-limit Level

0.00 0.05

-80dB

76%

0.05 0.10

-80dB

79%

0.10 0.15

-80dB

85%

0.15 0.20

-80dB

100%

0.20 0.25

-74dB

76%

0.25 0.30

-74dB

79%

0.30 0.35

-74dB

85%

0.35 0.40

-74dB

100%

0.40 0.45

-68dB

75%

0.45 0.50

-68dB

79%

0.50 0.55

-68dB

85%

0.55 0.60

-68dB

100%

0.60 0.65

-62dB

75%

0.65 0.70

-62dB

79%

0.70 0.75

-62dB

85%

0.75 0.80

-62dB

100%

0.80 0.85

MIS Off

75%

0.85 0.90

MIS Off

79%

0.90 0.95

MIS Off

85%

0.95 1.00

MIS Off

100%

T E C H N I C A L I N F O R M A T I O N

The TA2021-100 will quickly automatically come out of mute when it detects that the input
signal has gone above the preset level.

Input Limit

To "soften" the clipping characteristics of the TA2021-100 it will limit the audio signal to a pre-
determined, programmable input-limit level according to the voltage on the MIS/ADDR pin as
specified in the previous table. This limit is a percentage of the maximum possible output level.

Overload

When logic low, the OVRLD/SCL pin indicates that the level of the input signal has overloaded
the amplifier and that the audio output signal is starting to distort. The OVRLD/SCL signal is
active only while an overload is present. The OVRLD/SCL signal can be used to control a
distortion indicator light or LED through a simple buffer circuit.

Sleep

When a logic high signal is supplied to SLEEP, both amplifier channels are shut down and the
TA2021-100 is put into a low quiescent-current mode. When a logic level low is supplied to
MUTE, both amplifiers are fully operational.

Volume Control

A 5 M

potentiometer is used between V2BG, DCVOL and AGND (analog ground) to control

the output volume of both channels. When DCVOL is at the same level as V2BG, the output
volume is at 6 dB. When DCVOL is at the same level as GND, the output volume is at the
minimum, or 119.5 dB.

Auxiliary Outputs

The outputs AUXOUT1 and AUXOUT2 are analog-signal audio outputs in which the signal level
is controlled by the volume control. These outputs are capable of driving approximately 15mW
each into 20-ohm loads. These outputs are still active when the TA2021-100 is in mute mode,
even if the TA2021-100 is muted because no speaker is connected (see next section).

Speaker Detect

On power-up the TA2021-100 checks to make sure that speakers are connected to prevent
damage. If a speaker is not detected on either channel on power-up, the TA2021-100 keeps the
output stages of both amplifiers shut down (in mute) and signifies this fact by asserting a logic
level one on HMUTE/SDA. The TA2021-100 will come out of mute when speakers are
connected, even after a relatively long period of time (minutes after power-up).

T E C H N I C A L I N F O R M A T I O N

Functional Description Mode 2

Serial Bus Operation

When OVRLD/SCL is tied to V5 to a 5 k

resistor and the TA2021-100 senses this during power-

up it will go into Mode 2 operation, where control/status of the amplifier is by registers
accessed through a digital serial control bus. This serial bus is compatible with Philips' I

bus.

The TA2021-100 operates as a slave device on the bus. The OVRLD/SCL line is an input (no clock
is generated by the TA2021-100) and the HMUTE/SDA line is a bi-directional serial data path.

Six simple operations with the two lines of the serial bus are used for transmitting to or
receiving from a TA2021-100:

Start bit: A high-to-low transition of the data line while the clock line is in a high
state

Seven-bit slave address: The first seven bits following a start bit (MSB first)

Read/write bit which defines whether the slave is a transmitter or receiver: The next
bit immediately after the address is the direction of the transfer. A 0 indicates that
the master will write information to the slave. A 1 indicates that the master will
receive data from the slave.

Acknowledge bit: Every eight-bit byte transferred (including the eight bits
comprising the address and read/write bit) is followed by an acknowledge bit from
the receiver (the master generates all clock pulses). The transmitter releases the
data line during the acknowledge clock pulse. If there was no error detected, the
receiver will pull down the SDA line during the high period of the acknowledge
clock pulse. If a slave receiver is not able to acknowledge, the slave will keep the
SDA line high and the master can then generate a stop bit to abort the transfer. If a
master receiver keeps the SDA line high during the acknowledge clock pulse the
master is signaling the end of data transmission and the slave transmitter releases
the data line to allow the master to generate a stop bit.

Message bits divided into eight-bit bytes: One bit is transferred during each clock
pulse. The data must be stable during the high period of the clock. The data line
can only change when the clock line is low. The MSB of the byte is transmitted first.

Stop bit: A low-to-high transition of the data line while the clock line is in a high
state.

Slave ID Address

The TA2021-100 has a seven-bit slave ID address. The five most-significant bits of the slave
address are hardwired inside the TA2021-100 and are 10000. The two least-significant bits are
determined by the voltage on the MIS/ADDR pin according to the following table:

MIS/ADDR Pin Voltage

(Fraction of V5)

Address

0.00 0.25

A1 = 0, A0 = 0

0.25 0.50

A1 = 0, A0 = 1

0.50 0.75

A1 = 1, A0 = 0

0.75 1.00

A1 = 1, A0 = 1

T E C H N I C A L I N F O R M A T I O N

The complete slave address is:

MSB

LSB

The registers in the TA2021-100 are selected by the eight-bit index register. At power-up the
Index register is set to zero. The seven least-significant bits of the Index register define the
register address space in the TA2021-100. When a 1 is written to the MSB of the Index register
the Index register value is auto-incremented (by 1) after each byte transfer is complete. If a 0 is
written to the MSB of the Index register the Index register value is not changed.

The following table indicates the Index register address of each register:

STATUS

FAULT

INITIAL STATE

VOLUME ADC

CONTROL

CONFIGURATION

VOLUME1 (Channel 1)

VOLUME2 (Channel 2)

Test

Reserved

X = Don't care

All Test Registers/Bits should NOT be accessed as they are used for manufacturing test of the
TA2021-100 and can cause unexpected operation. All Reserved Registers/Bits are read-only with
a value of 0.

STATUS Register

ST7

ST6

ST5

ST4

ST3

ST2

ST1

ST0

Overload

Detect

Over-

current

Detect

Reserved

Mute In

Silence

Muted

Fault

ST7:

Overload detect. When 0, indicates normal operation. When 1, indicates that
the level of the audio input signal has overloaded the amplifier and that the
audio signal is starting to distort. This bit is read/write. Writing a 0 to it will
clear it.

ST6:

Over-current detect. When 0, indicates normal operation. When 1, indicates
that the voltage across R

has become greater than V

OC-LIMIT

, indicating an over-

current condition and the TA2021-100 is attempting to limit the current by
decreasing the input level using the volume control. This bit is read/write.
Writing a 0 to it will clear it.

T E C H N I C A L I N F O R M A T I O N

ST5:

Reserved. Read-only with a value of 0. Writing to it has no effect.

ST4:

Reserved. Read-only with a value of 0. Writing to it has no effect.

ST3:

Reserved. Read-only with a value of 0. Writing to it has no effect.

ST2:

Mute In Silence. When 0, indicates normal operation. When 1, indicates the sum
of the input levels of both channels is below the specified level for the
specified duration. This bit is read-only. Writing to it has no effect.

ST1:

Muted. When 0, indicates normal operation. When 1, indicates both outputs
are muted either due to an external control request or a fault condition has
been detected. This bit is read-only. Writing to it has no effect.

ST0:

Fault. When 0, indicated normal operation. When 1, indicates a fault has been
Detected. This bit is read-only. Writing to it has no effect.

FAULT Register

Reserved

Over-

current

fault

Power

Supply

Mute

Over-

temp.

Fault

Voltage

Fault

F7:

Reserved. Read-only with a value of 0. Writing to it has no effect.

F6:

Reserved. Read-only with a value of 0. Writing to it has no effect.

F5:

Reserved. Read-only with a value of 0. Writing to it has no effect.

F4:

Reserved. Read-only with a value of 0. Writing to it has no effect.

F3:

Over-current fault. When 0, indicates normal operation. When 1, indicates that
the voltage across R

has become greater than V

OC-SD

, indicating an over-current

fault and the TA2021-100 has shut down the output stages of its amplifiers. This
bit is read-only. Writing to it has no effect.

F2:

Power supply mute. When 0, indicates normal operation. When 1, indicates an
over-current condition has occurred, the TA2021-100 has shut down the output
stages of its amplifiers and the over-current situation still exists. This bit is read-
only. Writing to it has no effect.

F1:

Over-temperature fault. When 0, indicates normal operation. When 1, indicates
that the die temperature of the TA2021-100 has exceeded TBD. This bit is read-
only. Writing to it has no effect.

F0:

Voltage fault. When 0, indicates normal operation. When 1, indicates an over-/
under- voltage condition has shut down the TA2021-100. This bit is read-only.
Writing to it has no effect.

INITIAL STATE Register

IS7

IS6

IS5

IS4

IS3

IS2

IS1

IS0

Reserved

Speaker

Detect

Channel

Speaker

Detect

Channel

Reserved

Test

IS7:

Reserved. Read-only with a value of 0. Writing to it has no effect.

IS6:

Reserved. Read-only with a value of 0. Writing to it has no effect.

IS5:

Speaker detect channel 2. When 0, indicates that a speaker has been detected.

T E C H N I C A L I N F O R M A T I O N

When 1, indicates that a speaker has not been detected and the amplifier has
been muted. This bit is read-only. Writing to it has no effect.

IS4:

Speaker detect channel 1. When 0, indicates that a speaker has been detected.
When 1, indicates that a speaker has not been detected and the amplifier has
been muted. This bit is read-only. Writing to it has no effect.

IS3:

Reserved. Read-only with a value of 0. Writing to it has no effect.

IS2:

Test. Should not be accessed.

IS1:

Test. Should not be accessed.

IS0:

Test. Should not be accessed.

VOLUME ADC Register

MSB

LSB

V7-V0: Volume ADC. These bits provide a digital word value for the volume level set by

the voltage on the DCVOL pin. The resolution is 0.5dB per bit/step. All bits in
this register are read-only.

Volume/Gain

Maximum

Intermediate Level

Minimum

CONTROL Register

CTL7

CTL6

CTL5

CTL4

CTL3

CTL2

CTL1

CTL0

Mute

Sleep

Input

Select

Reserved

CTL7:

Mute. Writing a 0 to this bit (power-up initialization value) tells the TA2021-100
to operate normally. Writing a 1 to this bit tells the TA2021-100 to go into mute
mode, where the output stages of both amplifiers are shut down but all other
circuitry is still operational (including the volume control and AUXOUT audio
outputs. This bit is read/write.

CTL6:

Sleep. Writing a 0 to this bit (power-up initialization value) tells the TA2021-100
to operate normally. Writing a 1 to this bit shuts down both amplifiers and
most other circuitry in the TA2021-100 and puts the device in a low-power
mode. This bit is read/write.

CTL5:

Test. Should not be accessed.

CTL4:

Test. Should not be accessed.

CTL3:

Reserved. Read-only with a value of 0. Writing to it has no effect.

CTL2-CTL0: Input-limit level. The TA2021-100 will limit the audio signal to a percentage

of the maximum possible output level as specified by these bits in order to
"soften" its clipping characteristics. These bits are read/write.

T E C H N I C A L I N F O R M A T I O N

CTL2

CTL1

CTL0

Input-limit Level

73%

76%

78%

79%

82%

85%

88%

100%

CONFIGURATION Register

CFG7

CFG6

CFG5

CFG4

CFG3

CFG2

CFG1

CFG0

Test

Volume

Zero

Cross

Volume

Ramp

Volume

Control

Mode

MIS

Time 1

MIS

Time 0

MIS

Level 1

MIS

Level 0

CFG7: Test. Should not be accessed.

CFG6: Volume zero cross. Writing a 0 to this bit (power-up initialization value)
tells the TA2021-100 that volume changes can be made at any time. Writing a 1
to this bit tells. The TA2021-100 to only make volume changes at zero crossings
of the audio inputs.

CFG5: Volume ramp. Writing a 0 to this bit (power-up initialization value) tells the

TA2021-100 to implement any volume change requested immediately as
requested. Writing a 1 to this bit tells the TA2021-100 to implement any volume
at a rate of 40 msec per dB.

CFG4: Volume control mode. Writing a 0 to this bit (power-up initialization value) tells

the TA2021-100 to use the voltage on the DCVOL pin to directly control the
volume of both channels. Writing a 1 to this bit tells the TA2021-100 to use the
values in the VOLUME1 and VOLUME2 registers to set the output volumes of
the respective channels. This bit is read/write.
CFG3-CFG2: MIS time. These bits set the time interval during which the input
audio level must be below the specified level after which the TA2021-100 will
mute its outputs. These bits are read/write.

CFG3

CFG2

MIS Time

340 seconds (power-up initialization

value)

85 seconds

680 seconds

(MIS disabled)

CFG1-CFG0: MIS level. These bits set the audio level below which the input signal must

be for the TA2021-100 to mute its outputs after the specified time interval.
These bits are read/write.

CFG1

CFG0

MIS Level

-80dB (power-up initialization value)

T E C H N I C A L I N F O R M A T I O N

-74dB

-68dB

-62dB

VOLUME1 Register

V1R7

V1R6

V1R5

V1R4

V1R3

V1R2

V1R1

V1R0

MSB

LSB

V1R7-V1R0: Volume 1 (Channel 1). These bits set the output volume level for Channel 1

when the CFG4 bit in the CONFIGURATION register is set to 1. The resolution is
0.5dB per bit/step. The power-up initialization value is all ones. All bits in this
register are read/write.

V1R7 V1R6 V1R5 V1R4 V1R3 V1R2 V1R1 V1R0

Volume/Gain

Maximum (+4dB)

Minimum (-119.5dB)

VOLUME2 Register

V2R7

V2R6

V2R5

V2R4

V2R3

V2R2

V2R1

V2R0

MSB

LSB

V2R7-V2R0: Volume 2 (Channel 2). These bits set the output volume level for Channel 2

when the CFG4 bit in the CONFIGURATION register is set to 1. The resolution is
0.5dB per bit/step. The power-up initialization value is all ones. All bits in this
register are read/write.

V2R7 V2R6 V2R5 V2R4 V2R3 V2R2 V2R1 V2R0

Volume/Gain

Maximum (+4dB)

Minimum (-119.5dB)

Bus Transfer Sequences

To Be Supplied.

T E C H N I C A L I N F O R M A T I O N

Application Information

Power Supplies

The TA2021-100 requires the split supply rails VP1(VP2) and VN1(VN2), and +5V(VA). It also uses
some additional voltages, VGG, V

BOOT1

and V

BOOT2

, that it generates internally. The selection of

components for the switching regulator ... To Be Supplied

Supply Voltage and Output Power

The relationship between the bipolar power supply voltage needed, V

, for a given RMS output

power, P

OUT

, into a given load, R

, at a given level of THD (total harmonic distortion) is

approximated by:

= (2 x R

x P

OUT

)

0.5

/(K x R

/(R

+ R

COIL

))

where:
R

= The at-temperature R

DSON

of the output transistors, M.

COIL

= Resistance of the output filter inductor.

= Sense Resistor

K = THD Factor, a number fixed by the algorithms in the TA2021-100's signal processor

that provides the relationship between THD at full output power of the amplifier
and V

. K corresponds to THD at full output power as follows:

THD

0.1%

0.83

0.95

10%

1.09

Bridged Operation

Note that the two channels of a TA2021-100 amplifier can be used to provide a single, bridged
amplifier of almost four times the output power of one of the single-ended amplifier channels.
To configure a bridged amplifier, the input to one TA2021-100 channel must be the inverted
signal of the input to the other channel.

Low-frequency Power Supply Pumping

A potentially troublesome phenomenon in single-ended switching amplifiers is power supply
pumping. This is caused by current from the output filter inductor flowing into the power
supply output filter capacitors in the opposite direction as a DC load would drain current from
them. Under certain conditions (usually low-frequency input signals), this current can cause the
supply voltage to "pump" (increase) and eventually cause over-voltage/under-voltage shut
down. Moreover, since over/under-voltage are not "latched" shutdowns, the effect would be
an amplifier that oscillates between on and off states.

Even though the TA2021-100 has circuitry that nulls out any DC offset on power-up, a prudent
design will comprehend the power supply pumping issue. A no-cost solution uses the fact that
music has low frequency information that is correlated in both channels (it is in phase). This

T E C H N I C A L I N F O R M A T I O N

information can be used to eliminate boost by putting the two channels of a TA2021-100
amplifier out of phase with each other. This works because each channel is pumping out of
phase with the other, and the net effect is a cancellation of pumping currents in the power
supply. The phase of the audio signals needs to be corrected by connecting one of the speakers
in the opposite polarity as the other channel.

Amplifier Gain and Input Resistor Selection

The value of the input resistor, R

, is based on the required voltage gain, A

, of the amplifier

according to:

= 800 x10

/(R

+ 5000)

where R

= Input resistor value in ohms.

Input Capacitor Selection

can be calculated once a value for R

has been determined. C

and R

determine the input

low-frequency pole. Typically this pole is set at 10 Hz. C

is calculated according to:

= 1/(2

x F

)(R

+ 5000)

where:
R

= Input resistor value in ohms.

= Input low frequency pole (typically 10Hz).

DC Offset

The TA2021-100 has circuitry that nulls out any DC offset on power-up and external circuitry to
perform this function, as was necessary with the TA0102A and TA0103A, is no longer necessary.

It should be noted that the DC voltage on the output of a TA2021-100 amplifier with no load in mute mode is
approximately 2.5V. This offset does not need to be nulled. The output impedance of the amplifier in mute
mode is approximately 10 KOhms. This means that the 2.5V drops to essentially zero when a typical load is
connected.

Clamping Diodes

The purpose of the diodes across each of the output MOSFETs is to clamp the voltages the
MOSFET experiences to levels within its rating to prevent damage. Tripath recommends that
fast-recovery or schottky diodes be used for this purpose. The breakdown voltage rating of
this diode should be similar to that of the MOSFET. Also, the forward voltage drop of this
diode should be less than that of the internal body diode of the MOSFET.

Turn-on & Turn-off Noise

If turn-on or turn-off noise is present in a TA2021-100 amplifier, the cause is frequently due to
other circuitry external to the TA2021-100. While the TA2021-100 has circuitry to suppress
turn-on and turn-off transients, the combination of the power supply and other audio circuitry
with the TA2021-100 in a particular application may exhibit audible transients. One solution

T E C H N I C A L I N F O R M A T I O N

that will completely eliminate turn-on and turn-off pops and clicks is to use a relay to
connect/disconnect the amplifier from the speakers with the appropriate timing at power
on/off. The relay can also be used to protect the speakers from a component failure (e.g.
shorted output MOSFET), which is a protection mechanism that some amplifiers have. Circuitry
external to the TA2021-100 would need to be implemented to detect these failures.

Output Filter Design

One advantage of Tripath amplifiers over PWM solutions is the ability to use higher-cutoff-
frequency filters. This means any load-dependent peaking/droop in the 20kHz audio band
potentially caused by the filter can be made negligible. This is especially important for
applications where the user may select a 4-Ohm or 8-Ohm speaker. Furthermore, speakers are
not purely resistive loads and the impedance they present changes over frequency and from
speaker model to speaker model.

Tripath recommends designing the filter as a 2nd order, 80kHz LC filter. Tripath has obtained
good results with L

= 18uH and C

= 0.22uF.

The core material of the output filter inductor has an effect on the distortion levels produced
by a TA2021-100 amplifier. Tripath recommends low-mu type-2 iron powder cores because of
their low loss and high linearity.

Tripath also recommends that an RC damper be used after the LC low-pass filter. No-load
operation of a TA2021-100 amplifier can create significant peaking in the LC filter, which
produces strong resonant currents that can overheat the output MOSFETs and/or other
components. The RC dampens the peaking and prevents problems. Tripath has obtained good
results with R

= 33

and C

= 0.1uF.

It is highly recommended that the design process for a TA2021-100 amplifier include an analysis
of the interaction of intended speaker(s) with the LC filter and RC damper to ensure the
desired frequency response is attained. Component values for the LC filter and RC damper may
need to be altered from the Tripath suggestions to achieve the required response.

Grounding

To Be Supplied

Circuit Board Layout

Considerable care needs to be taken in the layout of the circuit board for a TA2021-100
amplifier. The high currents flowing through PCB traces and the inductive effects due to the
switching frequencies involved can cause large overshoot and undershoot voltages if care is not
taken. A general rule to follow is to keep the PCB trace of each signal path to/from each lead
of each output MOSFET as short as physically possible.

Certain circuit functions in a TA2021-100 amplifier cannot share PCB return paths with other
functions because of the resistive and inductive effects of the switching currents and
frequencies used. These so-called `Kelvin' paths must each have a dedicated PCB trace from the
TA2021-100 to their destination. GNDKELVIN1 and GNDKELVIN2 should be treated as Kelvin
paths.

T E C H N I C A L I N F O R M A T I O N

Performance Measurements of a TA2021-100 Amplifier

Tripath amplifiers operate by modulating the input signal with a high-frequency switching
pattern. This signal is sent through a low-pass filter (external to the Tripath amplifier) that
demodulates it to recover an amplified version of the audio input. The frequency of the
switching pattern is spread spectrum and typically varies between 200kHz and 1.5MHz, which is
well above the 20Hz 22kHz audio band. The pattern itself does not alter or distort the audio
input signal but it does introduce some inaudible noise components.

The measurements of certain performance parameters, particularly those that have anything to
do with noise, like THD+N, are significantly affected by the design of the low-pass filter used
on the output of the TA2021-100 and also the bandwidth setting of the measurement
instrument used. Unless the filter has a very sharp roll-off just past the audio band or the
bandwidth of the measurement instrument ends there, some of the inaudible noise
components introduced by the Tripath amplifier switching pattern will get integrated into the
measurement, degrading it.

One advantage of Tripath amplifiers is that they do not require large multi-pole filters to
achieve excellent performance in listening tests, usually a more critical factor than performance
measurements. Though using a multi-pole filter may remove high-frequency noise and
improve THD+N type measurements (when they are made with wide-bandwidth measuring
equipment), these same filters can increase distortion due to inductor non-linearity. Multi-pole
filters require relatively large inductors, and inductor non-linearity increases with inductor
value.

Efficiency Of A TA2021-100 Amplifier

The efficiency,

, of an amplifier is:

= P

OUT

The power dissipation of a TA2021-100 amplifier is primarily determined by the on resistance,
R

, of the output transistors used, and the switching losses of these transistors, P

. For a

TA2021-100 amplifier, P

(per channel) is approximated by:

= P

DRIVER

+ P

OUT

((R

+ R

COIL

+ R

)/R

)

where:

DRIVER

= Power dissipated in the TA2021-100 = 1.6W/channel

= 2 x (0.015) x Q

is the gate charge of M, in nano-coulombs)

COIL

= Resistance of the output filter inductor (typically around 50m

)

For a 100W RMS per channel, 8

load amplifier using an R

of 50m

= P

DRIVER

+ P

OUT

((R

+ R

COIL

+ R

)/R

)

= 1.6 + 2 x (0.015) x (95) + 100 x ((0.025 + 0.11 + 0.05 + 8)/8)

= 1.6 + 2.85 + 104.6
= 109.05

T E C H N I C A L I N F O R M A T I O N

ADVANCED DEVELOPMENT This is a product in development. Tripath Technology Inc. reserves
the right to make any changes without further notice to improve reliability, function or design.

This data sheet contains the design specifications for a product in development. Specifications may
change in any manner without notice. Tripath and Digital Power Processing are trademarks of
Tripath Technology Inc. Other trademarks referenced in this document are owned by their
respective companies

Tripath Technology Inc. reserves the right to make changes without further notice to any products
herein to improve reliability, function or design. Tripath does not assume any liability arising out of
the application or use of any product or circuit described herein; neither does it convey any license
under its patent rights, nor the rights of others.

TRIPATH'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN CONSENT OF THE PRESIDENT OF TRIPATH
TECHNOLOGY INC.
As used herein:
1.

Life support devices or systems are devices or systems which, (a) are intended for surgical

implant into the body, or (b) support or sustain life, and whose failure to perform, when properly
used in accordance with instructions for use provided in this labeling, can be reasonably expected
to result in significant injury to the user.
2.

A critical component is any component of a life support device or system whose failure to

perform can be reasonably expected to cause the failure of the life support device or system, or to
affect its safety or effectiveness.

TRIPATH TECHNOLOGY INC.
3900 Freedom Circle, Santa Clara, California 95054, 1-408-567-3000.
WWW.TRIPATH.COM

Document Outline

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: TA2021-100

Document Outline

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: TA2021-100