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TECHNICAL INFORMATION
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Stereo 20W (4) Class-T Digital Audio Amplifier using Digital Power ProcessingTM Technology TA2020-020
September, 2000
General Description
The TA2020-020 is a 20W continuous average two-channel Class-T Digital Audio Power TM Amplifier IC using Tripath's proprietary Digital Power Processing technology. Class-T amplifiers offer both the audio fidelity of Class-AB and the power efficiency of Class-D amplifiers.
Applications
DVD Players Mini/Micro Component Systems Automotive Audio Computer / PC Multimedia Cable Set-Top Products Televisions Battery Powered Systems
Features
Class-T architecture Single Supply Operation "Audiophile" Quality Sound 0.03% THD+N @ 10W 4 0.1% THD+N @12W 4 0.18% IHF-IM @ 1W 4 High Power 13W @ 8, 10% THD+N 23W @ 4, 10% THD+N 38W EIAJ* VDD=14.4V @ 4
*saturated square wave output
Benefits
Fully integrated solution with FETs Easier to design-in than Class-D Reduced system cost with no heat sink Dramatically improves efficiency versus Class-AB Signal fidelity equal to high quality linear amplifiers High dynamic range compatible with digital media such as CD, DVD, and internet audio
High Efficiency 88% @ 12W 8 81% @ 20W 4 Dynamic Range = 103 dB Up to 2X25Wrms @ 4, VDD=14.6V Mute and Sleep inputs Turn-on & turn-off pop suppression Over-current protection Over-temperature protection Bridged outputs 32-pin SSIP package
Typical Performance
THD+N versus Output Power
10 5 2 VDD = 13.5V Av = 12 f = 1kHz BW = 22Hz - 22kHz
THD+N (%)
1 0.5 0.2 0.1 0.05 0.02 0.01 500m 1 2 3 4 5 6 7 8 9 10 20
RL= 8
RL= 4
Output Power (W)
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TECHNICAL INFORMATION
Absolute Maximum Ratings (Note 1)
SYMBOL VDD TSTORE TA TJ Supply Voltage Storage Temperature Range Operating Free-air Temperature Range Junction Temperature PARAMETER
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Value 16 -40 to 150 -40 to 85 150 UNITS V C C C
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
Operating Conditions (Note 2)
SYMBOL VDD VIH VIL Supply Voltage High-level Input Voltage (MUTE, SLEEP) Low-level Input Voltage (MUTE, SLEEP) PARAMETER MIN. 8.5 3.5 1 TYP. 13.5 MAX. 14.6 UNITS V V V
Note 2: Recommended Operating Conditions indicate conditions for which the device is functional. See Electrical Characteristics for guaranteed specific performance limits.
Thermal Characteristics
SYMBOL JC JA PARAMETER Junction-to-case Thermal Resistance Junction-to-ambient Thermal Resistance Value 3.5 15 UNITS C/W C/W
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TECHNICAL INFORMATION
Electrical Characteristics (Note 1, 2)
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MIN. TYP. 13 8 22 12 5.5 0.25 60 0.03 0.18 89 74 60 80 80 88 50 3.5 1 150 7 2 MAX. UNITS W W W W mA mA mA % % dB dB dB % mV V V V
See Test/Application Circuit. Unless otherwise specified, VDD = 13.5V, f = 1kHz, Measurement Bandwidth = 22kHz, RL = 4, TA = 25 C.
SYMBOL PO PARAMETER Output Power (Continuous Average/Channel) CONDITIONS THD+N = 0.1% THD+N = 10% IDD,MUTE IDD, SLEEP Iq THD + N IHF-IM SNR CS PSRR VOFFSET VOH VOL eOUT Mute Supply Current Sleep Supply Current Quiescent Current Total Harmonic Distortion Plus Noise IHF Intermodulation Distortion Signal-to-Noise Ratio Channel Separation Power Supply Rejection Ratio Power Efficiency Output Offset Voltage High-level output voltage (FAULT & OVERLOADB) Low-level output voltage (FAULT & OVERLOADB) Output Noise Voltage MUTE = VIH SLEEP = VIH VIN = 0 V PO = 10W/Channel 19kHz, 20kHz, 1:1 (IHF) A-Weighted, POUT = 1W, RL = 8 0dBr = 1W, RL = 4, f = kHz Vripple = 100mV POUT = 12W/Channel, RL = 8 No Load, MUTE = Logic low RL = 4 RL = 8 RL = 4 RL = 8
A-Weighted, input AC grounded
100
Notes: 1) Minimum and maximum limits are guaranteed but may not be 100% tested. 2) For operation in ambient temperatures greater than 25C, the device must be derated based on the maximum junction temperature and the thermal resistance determined by the mounting technique.
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TECHNICAL INFORMATION
Pin Description
Pin 2, 8 3, 7, 16 4 6 9, 12 10, 13 11 14 17 18 19, 28 20 21, 23, 26, 24 22, 25 1, 5, 15 27 29 30 31, 32 Function V5D, V5A AGND1, AGND2, AGND3 REF OVERLOADB VP1, VP2 IN1, IN2 MUTE BIASCAP SLEEP FAULT PGND2, PGND1 DGND OUTP2 & OUTM2; OUTP1 & OUTM1 VDD2, VDD1 NC VDDA CPUMP 5VGEN DCAP2, DCAP1 Description Digital 5VDC, Analog 5VDC Analog Ground
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Internal reference voltage; approximately 1.0VDC A logic low output indicates the input signal has overloaded the amplifier. Input stage output pins Single-ended inputs. Inputs are a "virtual" ground of an inverting opamp with approximately 2.4VDC bias. When set to logic high, both amplifiers are muted and in idle mode. When low (grounded), both amplifiers are fully operational. If left floating, the device stays in the mute mode. Ground if not used. Input stage bias voltage (approximately 2.4VDC). When set to logic high, device goes into low power mode. If not used this pin should be grounded. A logic high output indicates thermal overload, or an output is shorted to ground, or another output. Power Ground (high current) Digital Ground Bridged outputs Supply pin for high current H-bridges, nominally 13.5VDC. Not connected Analog 13.5VDC Charge pump output (nominally 10V above VDDA) Regulated 5VDC source used to supply power to the input section (pins 2 & 8). Charge pump switching pins. DCAP1 (pin 32) is a free running 300kHz square wave between VDDA and DGND (13.5Vpp nominal). DCAP2 (pin 31) is level shifted 10 volts above DCAP1 (pin 32) with the same amplitude (13.5Vpp nominal), frequency, and phase as DCAP1.
32-pin SSIP Package (Front View)
NC V5D AGND1 REF NC OVERLOADB AGND2 V5A VP1 IN1 MUTE VP2 IN2 BIASCAP NC AGND3 SLEEP FAULT PGND2 DGND OUTP2 VDD2 OUTM2 OUTM1 VDD1 OUTP1 VDDA PGND1 CPUMP 5VGEN DCAP2 DCAP1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
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TECHNICAL INFORMATION
Application/Test Circuit
TA2020-020
1
RF 20K VP1 VDD1 NC Lo 10uH, 3A
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9 Processing & Modulation
26
OUTP1
CI 2.2uF +
DO
PGND1 VDD1 (Pin 28) (Pin 28) *Co 0.47uF
IN1 RI 20K
10
CZ 0.47uF
CCM 0.1uF
CA 0.1uF (Pin 7) 5V
BIASCAP
14
5V
24 OUTM1 DO
Lo 10uH, 3A
*Co 0.47uF
RZ 10, 1/2W
RL 4 or *8
11
MUTE
PGND1
(Pin 28)
18 6
VDD2
FAULT OVERLOADB
CI 2.2uF +
RF 20K
VP2 12
IN2 RI 20K
13 Processing & Modulation
21
OUTP2
Lo 10uH, 3A
(Pin 3)
4
RREF 8.25K, 1%
DO
PGND2 VDD2 (Pin 19) (Pin 19)
REF
*Co 0.47uF
CZ 0.47uF CCM 0.1uF
+12V CD 0.1uF 1meg
32 DCAP1 31 DCAP2 17 5 2
CS 0.1uF SLEEP CPUMP
23 OUTM2 DO
PGND2 (Pin 19) Lo 10uH, 3A
*Co 0.47uF
RZ 10, 1/2W
RL 4 or *8
29
+
0.1uF
NC
5V
VDDA 27 DGND
CP 1uF CS 0.1uF CS 0.1uF To Pin 2,8
20
V5D AGND1 V5A
3 8
5VGEN 30 VDD1 25 PGND1 28
To Pin 30 CS 0.1uF
7 AGND2 15 NC 16 AGND3
CSW 0.1uF
+
VDD (+13.5V) CSW
180uF, 16V
22 VDD2
PGND2 19
CSW 0.1uF
+
CSW 180uF, 16V
Note: Analog and Digital/Power Grounds must be connected locally at the TA2020-020 Analog Ground Digital/Power Ground All Diodes Motorola MBRS130T3 * Use Co = 0.22F for 8 Ohm loads
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TECHNICAL INFORMATION
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External Components Description (Refer to the Application/Test Circuit)
Components RI RF CI RREF CA CD CP Description Inverting input resistance to provide AC gain in conjunction with RF. This input is biased at the BIASCAP voltage (approximately 2.4VDC). Feedback resistor to set AC gain in conjunction with RI; A V = 12(RF / RI ) . Please refer to the Amplifier Gain paragraph, in the Application Information section. AC input coupling capacitor which, in conjunction with RI, forms a highpass filter at
fC = 1 ( 2RICI )
CS CSW
CZ RZ
DO
LO
Bias resistor. Locate close to pin 4 and ground at pin 7. BIASCAP decoupling capacitor. Should be located close to pin 14 and grounded at pin 7. Charge pump input capacitor. This capacitor should be connected directly between pins 31 and 32 and located physically close to the TA2020-020. Charge pump output capacitor that enables efficient high side gate drive for the internal H-bridges. To maximize performance, this capacitor should be connected directly between pin 29 (CPUMP) and pin 27 (VDDA). Please observe the polarity shown in the Application/Test Circuit. Supply decoupling for the low current power supply pins. For optimum performance, these components should be located close to the pin and returned to their respective ground as shown in the Application/Test Circuit. Supply decoupling for the high current H-Bridge supply pins. These components must be located as close to the device as possible to minimize supply overshoot and maximize device reliability. Both the high frequency bypassing (0.1uF) and bulk capacitor (180uF) should have good high frequency performance including low ESR and low ESL. Panasonic HFQ or FC capacitors are ideal for the bulk capacitor. Zobel capacitor, which in conjunction with RZ, terminates the output filter at high frequencies Zobel resistor, which in conjunction with CZ, terminates the output filter at high frequencies. The combination of RZ and CZ minimizes peaking of the output filter under both no load conditions or with real world loads, including loudspeakers which usually exhibit a rising impedance with increasing frequency. Depending on the program material, the power rating of RZ may need to be adjusted. The typical value is 1/2 watt. Schottky diodes that minimize undershoots of the outputs with respect to power ground during switching transitions. For maximum effectiveness, these diodes must be located close to the output pins and returned to their respective PGND. Please see Application/Test Circuit for ground return pin. Output inductor, which in conjunction with CO, demodulates (filters) the switching waveform into an audio signal. Forms a second order filter with a cutoff frequency of and a quality factor of Q = R L C O L O C O . Output capacitor which in conjunction with LO, demodulates (filters) the switching waveform into an audio signal. Forms a second order low-pass filter with a cutoff frequency of f C = 1 ( 2 L O C O ) and a quality factor of Q = R L C O L O C O . Common mode capacitor.
CO
CCM
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TECHNICAL INFORMATION
Typical Performance Characteristics
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100 90 80 70
Efficiency versus Output Power
RL = 8
Channel Separation versus Frequency
+0 -10 VDD = 13.5V Pout = 1W/Channel RLoad = 4 Av = 12 BW = 22Hz - 22kHz
Channel Separation (dBr)
VDD = 13.5V f = 1kHz Av = 12
-20 -30 -40 -50 -60 -70 -80 -90 -100
Efficiency (%)
RL = 4
60 50 40 30 20 10 0 0 5 10
20
50
100
200
500
1k
2k
5k
10k
20k
Output Power (W)
15
20
25
30
Frequency (Hz)
Intermodulation Performance
+0 -10 -20 -30 VDD = 13.5V Pout = 1W/Channel RLoad = 4W 19kHz, 20kHz, 1:1 0dBr = 12Vrms Av = 12 BW = 10Hz - 80kHz +0 -10 -20 -30 -40 -50
Noise Floor
VDD = 13.5V Pout = 0W Av = 12 RLoad = 4 BW = 20Hz - 22kHz A-Weighted Filter
-40 -50 -60 -70 -80 -90 -100 50 1k 2k 5k 10k 20k 30k
Noise FFT (dBV)
FFT (dBr)
-60 -70 -80 -90 -100 -110 -120 -130 -140 -150 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency (Hz)
Frequency (Hz)
THD+N versus Frequency
10 5 2 1 VDD = 13.5V Pout = 5W/Channel Av = 12 BW = 22Hz - 22kHz
Frequency Response
+3 +2.5 VDD = 13.5V Pout = 1W RLoad = 4 Av = 12 BW = 22Hz - 22kHz
Output Amplitude (dBr)
RL = 8
100 200 500 1k 2k 5k 10k 20k
+2 +1.5 +1 +0.5 +0 -0.5 -1 -1.5 -2 -2.5
THD+N (%)
0.5
0.2 0.1
0.05
0.02 0.01
RL = 4
10
20
50
-3 10 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency (Hz)
Frequency (Hz)
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TECHNICAL INFORMATION
Application Information
Circuit Board Layout
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The TA2020-020 is a power (high current) amplifier that operates at relatively high switching frequencies. The outputs of the amplifier switch between the supply voltage and ground at high speeds while driving high currents. This high-frequency digital signal is passed through an LC lowpass filter to recover the amplified audio signal. Since the amplifier must drive the inductive LC output filter and speaker loads, the amplifier outputs can be pulled above the supply voltage and below ground by the energy in the output inductance. To avoid subjecting the TA2020-020 to potentially damaging voltage stress, it is critical to have a good printed circuit board layout. It is recommended that Tripath's layout and application circuit be used for all applications and only be deviated from after careful analysis of the effects of any changes. The figures below are the Tripath TA2020-020 evaluation board. Some of the most critical components on the board are the power supply decoupling capacitors. C674 and C451 must be placed right next to pins 22 and 19 as shown. C673 and C451B must be placed right next to pins 25 and 28 as shown. These power supply decoupling capacitors from the output stage not only help reject power supply noise, but they also absorb voltage spikes on the VDD pins caused by overshoots of the outputs of the amplifiers. Voltage overshoots can also be caused by output inductor flyback during high current switching events such as shorted outputs or driving low impedances at high levels. If these capacitors are not close enough to the pins, electrical overstress to the part can occur, possibly resulting in permanent damage to the TA2020-020.
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TECHNICAL INFORMATION
Amplifier Gain
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The gain of the TA2020-020 is set by the ratio of two external resistors, RI and RF, and is given by the following formula:
VO R = 12 F VI RI
where VI is the input signal level and VO is the differential output signal level across the speaker. 20 watts of RMS output power results from an 8.944 V RMS signal across a four-ohm speaker load. If RF = RI, then 20 Watts will be achieved with 0.745 V RMS of input signal.
8.944 VRMS = (R L PO ) = ( 4 20 W )
Protection Circuits The TA2020-020 is guarded against over-temperature and over-current conditions. When the device goes into an over-temperature or over-current state, the FAULT pin goes to a logic HIGH state indicating a fault condition. When this occurs, the amplifier is muted, all outputs are TRISTATED, and will float to 1/2 of VDD. Over-temperature Protection An over-temperature fault occurs if the junction temperature of the part exceeds approximately 155C. The thermal hysteresis of the part is approximately 45C, therefore the fault will automatically clear when the junction temperature drops below 110C. Over-current Protection An over-current fault occurs if more than approximately 7 amps of current flows from any of the amplifier output pins. This can occur if the speaker wires are shorted together or if one side of the speaker is shorted to ground. An over-current fault sets an internal latch that can only be cleared if the MUTE pin is toggled or if the part is powered down. Alternately, if the MUTE pin is connected to the FAULT pin, the HIGH output of the FAULT pin will toggle the MUTE pin and automatically reset the fault condition. Overload The OVERLOADB pin is a 5V logic output. When low, it indicates that the level of the input signal has overloaded the amplifier resulting in increased distortion at the output. The OVERLOADB signal can be used to control a distortion indicator light or LED through a simple buffer circuit. Sleep Pin The SLEEP pin is a 5V logic input that when pulled high (>3.5V) puts the part into a low quiescent current mode. This pin is internally clamped by a zener diode to approximately 6V thus allowing the
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TECHNICAL INFORMATION
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pin to be pulled up through a large valued resistor (1M recommended) to VDD. To disable SLEEP mode, the sleep pin should be grounded. Fault Pin The FAULT pin is a 5V logic output that indicates various fault conditions within the device. These conditions include: low supply voltage, low charge pump voltage, low 5V regulator voltage, over current at any output, and junction temperature greater than approximately 155C. The FAULT output is capable of directly driving an LED through a series 200. The FAULT output is capable of directly driving an LED through a series 200 resistor. If the FAULT pin is connected directly to the MUTE input an automatic reset will occur in the event of an over-current condition. Heat Sink Requirements In some applications it may be necessary to fasten the TA2020-020 to a heat sink. The determining factor is that the 150C maximum junction temperature, TJ(max) cannot be exceeded, as specified by the following equation:
PDISS =
(T
J ( MAX )
- TA )
JA
where... PDISS = maximum power dissipation TJMAX = maximum junction temperature of TA2020-020 TA = operating ambient temperature JC = junction-to-case thermal resistance of TA2020-020 Example: What size heat sink is required to operate the TA2020-020 at 20W per channel continuously in a 70C ambient temperature? PDISS is determined by: Efficiency = =
POUT POUT = PIN POUT - PDISS
POUT 20 - POUT = - 20 = 5 W 0 .8
PDISS (per channel) =
Thus, PDISS for two channels = 10W JA =
(T
J ( MAX )
- TA )
PDISS
=
150 - 70 = 8C/W 10
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TECHNICAL INFORMATION
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The JA of the TA2020-020 in free air is 15C/W. The JC of the TA2020-020 is 3.5C/W, so a heat sink of 4.5C/W is required for this example. In actual applications, other factors such as the average PDISS with a music source (as opposed to a continuous sine wave) and regulatory agency testing requirements will determine the size of the heat sink required. Performance Measurements of the TA2020-020 The TA2020-020 operates by generating a high frequency switching signal based on the audio input. This signal is sent through a low-pass filter (external to the Tripath amplifier) that recovers an amplified version of the audio input. The frequency of the switching pattern is spread spectrum in nature and typically varies between 100kHz and 1MHz, which is well above the 20Hz - 20kHz audio band. The pattern itself does not alter or distort the audio input signal, but it does introduce some inaudible components. The measurements of certain performance parameters, particularly noise related specifications such as THD+N, are significantly affected by the design of the low-pass filter used on the output as well as the bandwidth setting of the measurement instrument used. Unless the filter has a very sharp roll-off just beyond the audio band or the bandwidth of the measurement instrument is limited, some of the inaudible noise components introduced by the TA2020-020 amplifier switching pattern will degrade the measurement. One feature of the TA2020-020 is that it does 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 degrade frequency response. The TA2020-020 Evaluation Board uses the Application/Test Circuit of this data sheet, which has a simple two-pole output filter and excellent performance in listening tests. Measurements in this data sheet were taken using this same circuit with a limited bandwidth setting in the measurement instrument.
TA2020-020, Rev. 4.0, 09.00
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TECHNICAL INFORMATION
Package Information
32-pin SSIP Package:
B
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TECHNICAL INFORMATION
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ADVANCED INFORMATION - 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. 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. For more information on Tripath products, visit our web site at: www.tripath.com World Wide Sales Offices Western United States: Jim Hauer Taiwan, HK, China: Jim Hauer Japan: Osamu Ito Europe: Steve Tomlinson
jhauer@tripath.com jhauer@tripath.com ito@tripath.com stomlinson@tripath.com
408-567-3089 408-567-3089 81-42-334-2433 44-1672-86-1020
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TRIPATH TECHNOLOGY, INC. 3900 Freedom Circle, Suite 200 Santa Clara, California 95054 408-567-3000
TA2020-020, Rev. 4.0, 09.00
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