TP2350 [TRIPATH]

Interface Circuit;
TP2350
型号: TP2350
厂家: TRIPATH TECHNOLOGY INC.    TRIPATH TECHNOLOGY INC.
描述:

Interface Circuit

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Tripath Technology, Inc. - Technical Information  
TK2350  
STEREO 300W (4) CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER  
USING DIGITAL POWER PROCESSINGTM TECHNOLOGY  
T e c h n i c a l I n f o r m a t i o n  
R e vi s i o n 1 . 4 – Ap r i l 2 0 0 3  
GENERAL DESCRIPTION  
The TK2350 (TC2001/TP2350B chipset) is a two-channel, 300W (4) per channel Amplifier Driver that uses  
Tripath’s proprietary Digital Power Processing (DPPTM) technology. Class-T amplifiers offer both the audio  
fidelity of Class-AB and the power efficiency of Class-D amplifiers.  
Applications  
Features  
Audio/Video Amplifiers & Receivers  
Pro-audio Amplifiers  
Class-T architecture  
Pin compatible with Tripath TK2150  
Proprietary Digital Power Processing technology  
“Audiophile” Sound Quality  
Automobile Power Amplifiers  
Subwoofer Amplifiers  
0.02% THD+N @ 50W, 8Ω  
0.03% IHF-IM @ 30W, 8Ω  
Benefits  
High Efficiency  
Reduced system cost with smaller/less  
95% @ 150W @ 8Ω  
90% @ 275W @ 4Ω  
expensive power supply and heat sink  
Signal fidelity equal to high quality Class-AB  
amplifiers  
Supports wide range of output power levels  
Up to 300W/channel (4), single-ended  
outputs  
High dynamic range compatible with digital  
media such as CD and DVD  
Up to 1000W (4), bridged outputs  
Output over-current protection  
Over- and under-voltage protection  
Over-temperature protection  
Typical Performance for TK2350  
THD+N versus Output Power versus Supply Voltage  
RL = 4Ω  
10  
5
f = 1kHz  
BBM = 80nS  
BW = 22Hz - 22kHz  
2
1
39V  
45V  
54V  
0.5  
0.2  
0.1  
0.05  
0.02  
0.01  
1
2
5
10  
20  
50  
100  
200  
500  
Output Power (W)  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Absolute Maximum Ratings TC2001 (Note 1)  
SYMBOL  
V5  
Vlogic  
TA  
TSTORE  
TJMAX  
ESDHB  
PARAMETER  
Value  
6
V5+0.3V  
-40° to +85°  
-55° to 150°  
150°  
UNITS  
V
V
°C  
°C  
5V Power Supply  
Input Logic Level  
Operating Free-air Temperature Range  
Storage Temperature Range  
Maximum Junction Temperature  
ESD Susceptibility – Human Body Model (Note 2)  
All pins  
°C  
2000  
V
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.  
See the table below for Operating Conditions.  
Note 2: Human body model, 100pF discharged through a 1.5Kresistor.  
Absolute Maximum Ratings TP2350B (Note 3)  
SYMBOL  
VPP, VNN Supply Voltage  
VN10  
TSTORE  
TA  
PARAMETER  
Value  
+/- 70  
VNN+13  
-55º to 150º  
-40º to 85º  
150º  
UNITS  
V
V
C
C
C
Voltage for FET drive  
Storage Temperature Range  
Operating Free-air Temperature Range  
Junction Temperature  
TJ  
ESDHB  
ESD Susceptibility – Human Body Model (Note 4)  
All pins  
2000  
200  
V
V
ESDMM  
ESD Susceptibility – Machine Model (Note 5)  
All pins  
Note 3: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.  
See the table below for Operating Conditions.  
Note 4: Human body model, 100pF discharged through a 1.5Kresistor.  
Note 5: Machine model, 220pF – 240pF discharged through all pins.  
Operating Conditions TC2001 (Note 6)  
SYMBOL  
V5  
VHI  
VLO  
TA  
PARAMETER  
MIN.  
4.5  
V5-1.0  
TYP.  
5
MAX. UNITS  
Supply Voltage  
Logic Input High  
Logic Input Low  
5.5  
V
V
V
C
1
Operating Temperature Range  
-40°  
25°  
85°  
Note 6: Recommended Operating Conditions indicate conditions for which the device is functional.  
See Electrical Characteristics for guaranteed specific performance limits.  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Operating Conditions TP2350B (Note 7)  
SYMBOL  
VPP, VNN Supply Voltage  
VN10  
PARAMETER  
MIN.  
+/- 15 +/-45 +/- 65  
10 12  
TYP.  
MAX. UNITS  
V
V
Voltage for FET drive (Volts above VNN)  
9
Note 7: Recommended Operating Conditions indicate conditions for which the device is functional.  
See Electrical Characteristics for guaranteed specific performance limits.  
Operating Characteristics TC2001 (Note 8)  
SYMBOL  
I5  
PARAMETER  
MIN.  
TYP.  
50  
MAX. UNITS  
Supply Current  
mA  
fsw  
VIN  
VOUTHI  
VOUTLO  
RIN  
Switching Frequency  
Input Sensitivity  
High Output Voltage  
Low Output Voltage  
Input Impedance  
Input DC Bias  
650  
kHz  
V
V
0
1.5  
V5-0.5  
100  
mV  
2
2.4  
k
V
Note 8: Recommended Operating Conditions indicate conditions for which the device is functional.  
See Electrical Characteristics for guaranteed specific performance limits.  
Thermal Characteristics TC2001  
SYMBOL  
PARAMETER  
Value  
UNITS  
Junction-to-ambient Thermal Resistance (still air)  
C/W  
θ
JA  
80°  
Thermal Characteristics TP2350B  
SYMBOL  
PARAMETER  
Value  
UNITS  
Junction-to-case Thermal Resistance (Note 9)  
C/W  
θ
JC  
3°  
Note 9: Recommended Operating Conditions indicate conditions for which the device is functional.  
See Electrical Characteristics for guaranteed specific performance limits.  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Electrical Characteristics TC2001 (Note 10)  
TA = 25 °C. See Application/Test Circuit on page 7. Unless otherwise noted, the supply voltage is  
VPP=|VNN|=45V.  
SYMBOL  
Iq  
PARAMETER  
CONDITIONS  
MIN.  
TYP.  
45  
MAX. UNITS  
Quiescent Current  
V5 = 5V  
V5 = 5V  
60  
mA  
(Mute = 0V)  
IMUTE  
Mute Supply Current  
(Mute = 5V)  
20  
25  
mA  
VIH  
VIL  
VOH  
VOL  
VTOC  
High-level input voltage (MUTE)  
3.5  
4.0  
V
V
V
V
V
Low-level input voltage (MUTE)  
High-level output voltage (HMUTE) IOH = 3mA  
Low-level output voltage (HMUTE) IOL = 3mA  
1.0  
0.5  
1.09  
Over Current Sense Voltage  
TBD  
0.85  
0.97  
Threshold  
IVPPSENSE VPPSENSE Threshold Currents  
Over-voltage turn on (muted)  
Over-voltage turn off (mute off)  
Under-voltage turn off (mute off)  
Under-voltage turn on (muted)  
Over-voltage turn on (muted)  
Over-voltage turn off (mute off)  
Under-voltage turn off (mute off)  
Under-voltage turn on (muted)  
Over-voltage turn on (muted)  
Over-voltage turn off (mute off)  
Under-voltage turn off (mute off)  
Under-voltage turn on (muted)  
162  
154  
79  
178  
87  
µA  
µA  
µA  
µA  
V
138  
62  
72  
VVPPSENSE Threshold Voltages with  
RVPPSENSE = 422KΩ  
68.4  
65.0  
33.3  
30.4  
174  
169  
86  
75.8  
37.1  
191  
95  
57.6  
25.9  
152  
65  
V
V
(Note 11, Note 12)  
V
IVNNSENSE VNNSENSE Threshold Currents  
µA  
µA  
µA  
µA  
V
77  
VVNNSENSE Threshold Voltages with  
RVNNSENSE = 392KΩ  
Over-voltage turn on (muted)  
Over-voltage turn off (mute off)  
Under-voltage turn off (mute off)  
Under-voltage turn on (muted)  
-68.2  
-66.2  
-33.7  
-30.2  
-75.6  
-37.6  
-59.0  
-25.2  
V
V
(Note 11, Note 12)  
V
Note 10: Minimum and maximum limits are guaranteed but may not be 100% tested.  
Note 11: These supply voltages are calculated using the IVPPSENSE and IVNNSENSE values shown in the Electrical  
Characteristics table. The typical voltage values shown are calculated using a RVPPSENSE and RVNNSENSE value  
of 422kohm without any tolerance variation. The minimum and maximum voltage limits shown include either a +1% or  
–1% (+1% for Over-voltage turn on and Under-voltage turn off, -1% for Over-voltage turn off and Under-voltage turn on)  
variation of RVPPSENSE or RVNNSENSE off the nominal 422kohm and 392kohm values. These voltage  
specifications are examples to show both typical and worst case voltage ranges for a given RVPPSENSE and  
RVNNSENSE resistor values of 422kohm and 392kohm. Please refer to the Application Information section for a more  
detailed description of how to calculate the over and under voltage trip voltages for a given resistor value.  
Note 12: The fact that the over-voltage turn on specifications exceed the absolute maximum of +/-70V for the TK2350 does not  
imply that the part will work at these elevated supply voltages. It also does not imply that the TK2350 is tested or  
guaranteed at these supply voltages. The supply voltages are simply a calculation based on the process spread of the  
IVPPSENSE and IVNNSENSE currents (see note 7). The supply voltage must be maintained below the absolute  
maximum of +/-70V or permanent damage to the TK2350 may occur.  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Electrical Characteristics TK2350 (Note 14)  
TA = 25 °C. See Application/Test Circuit on page 7. Unless otherwise noted, the supply voltage is  
VPP=|VNN|=45V.  
SYMBOL  
Iq  
PARAMETER  
CONDITIONS  
VPP = +45V  
MIN.  
TYP.  
MAX. UNITS  
Quiescent Current  
90  
mA  
mA  
mA  
(No load, BBM0=1,BBM1=0,  
Mute = 0V)  
VNN = -45V (using external VN10)  
VNN = -45V (using SMPSO pin to  
drive IRF9510 for generating VN10)  
VN10 = 10V  
90  
TBD  
200  
1
TBD  
mA  
mA  
mA  
mA  
IMUTE  
Mute Supply Current  
(No load, Mute = 5V)  
VPP = +45V  
VNN = -45V  
1
VN10 = 10V  
1
Note 14: Minimum and maximum limits are guaranteed but may not be 100% tested.  
Performance Characteristics TK2350 – Single Ended  
TA = 25 °C. Unless otherwise noted, the supply voltage is VPP=|VNN|=45V, the input frequency is 1kHz and the  
measurement bandwidth is 20kHz. See Application/Test Circuit.  
SYMBOL  
POUT  
PARAMETER  
Output Power  
(continuous Power/Channel)  
CONDITIONS  
THD+N = 0.1%, RL = 8Ω  
MIN.  
TYP.  
MAX. UNITS  
100  
190  
120  
220  
0.02  
0.03  
102  
W
W
W
W
RL = 4Ω  
THD+N = 1%,  
RL = 8Ω  
RL = 4Ω  
THD + N Total Harmonic Distortion Plus  
Noise  
IHF-IM  
SNR  
CS  
%
POUT = 50W/Channel, RL = 8Ω  
IHF Intermodulation Distortion  
%
19kHz, 20kHz, 1:1 (IHF), RL = 8Ω  
POUT = 30W/Channel  
Signal-to-Noise Ratio  
dB  
A Weighted, RL = 4,  
POUT = 275W/Channel  
Channel Separation  
Power Efficiency  
Amplifier Gain  
97  
95  
10.7  
dB  
%
V/V  
0dBr = 30W, RL = 8, f = 1kHz  
POUT = 150W/Channel, RL = 8Ω  
η
AV  
P
OUT = 10W/Channel, RL = 4Ω  
See Application / Test Circuit  
AVERROR  
eNOUT  
Channel to Channel Gain Error  
Output Noise Voltage  
0.5  
1.0  
dB  
P
OUT = 10W/Channel, RL = 4Ω  
See Application / Test Circuit  
A Weighted, no signal, input shorted,  
DC offset nulled to zero  
260  
µV  
VOFFSET  
Output Offset Voltage  
No Load, Mute = Logic Low  
0.1% RFBA, RFBB, RFBC resistors  
-1.0  
V
5 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TK2350 Block Diagram  
LC  
Output Left  
Input Left  
TC2001  
Audio  
Filter  
TP2350B  
MOSFET  
Driver  
Output  
MOSFETs  
Signal  
LC  
Filter  
Processor  
Input Right  
Output Right  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TC2001 Pinout  
28-pin SOIC  
(Top View)  
28  
27  
26  
1
2
3
4
5
6
7
8
BIASCAP  
FBKGND2  
DCMP  
FBKOUT2  
VPWR  
FBKGND1  
FBKOUT1  
HMUTE  
Y1  
INV2  
OAOUT2  
BBM0  
BBM1  
MUTE  
INV1  
OAOUT1  
V5  
AGND  
VPPSENSE  
OVRLDB  
VNNSENSE  
OCD1  
REF  
25  
24  
23  
22  
21  
20  
19  
18  
9
10  
11  
12  
13  
14  
Y1B  
Y2B  
Y2  
NC  
17  
16  
15  
OCD2  
TP2350B Pinout  
64-pin LQFP  
(Top View)  
51 50 49 48 47  
40 39 38  
36 35 34 33  
37  
46 45 44 43 42 41  
52  
53  
54  
55  
56  
57  
58  
59  
60  
61  
62  
63  
64  
32  
31  
30  
29  
28  
27  
26  
25  
24  
23  
22  
21  
20  
NC  
OCS1LN  
NC  
OCS2LN  
OCS2LP  
NC  
NC  
VBOOT2  
OCS1LP  
NC  
NC  
VBOOT1  
NC  
SW -FB  
SMPSO  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
1
2
3
4
5
6
7
8
9
15 16 17 18 19  
10 11 12 13 14  
Please note that the heatslug on the bottom of the package is connected to VNN.  
7 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TC2001 Audio Signal Processor Pin Descriptions  
Pin  
Function  
Description  
1
BIASCAP  
Bandgap reference times two (typically 2.5VDC). Used to set the  
common mode voltage for the input op amps. This pin is not capable of  
driving external circuitry.  
2, 6  
3
FBKGND2,  
FBKGND1  
DCMP  
Ground Kelvin feedback (Channels 1 & 2)  
Internal mode selection. This pin must be grounded for proper device  
operation.  
4, 7  
FBKOUT2,  
FBKOUT1  
VPWR  
Switching feedback (Channels 1 & 2)  
5
8
Test pin. Must be left floating.  
HMUTE  
Logic output. A logic high indicates both amplifiers are muted, due to the  
mute pin state, or a “fault”.  
9, 12  
10, 11  
13  
Y1, Y2  
Y1B, Y2B  
NC  
Non-inverted switching modulator outputs.  
Inverted switching modulator outputs.  
No connect  
14, 16  
15  
OCD2, OCD1  
REF  
Over Current Detect pins.  
Internal bandgap reference voltage; approximately 1.2 VDC.  
Negative supply voltage sense input. This pin is used for both over and  
under voltage sensing for the VNN supply.  
A logic low output indicates the input signal has overloaded the amplifier.  
Positive supply voltage sense input. This pin is used for both over and  
under voltage sensing for the VPP supply.  
Analog Ground.  
17  
VNNSENSE  
18  
19  
OVRLDB  
VPPSENSE  
20  
AGND  
V5  
21  
5 Volt power supply input.  
22, 27  
23, 28  
OAOUT1, OAOUT2 Input stage output pins.  
INV1, INV2  
Single-ended inputs. Inputs are a “virtual” ground of an inverting opamp  
with approximately 2.4VDC bias.  
24  
MUTE  
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.  
Break-before-make timing control to prevent shoot-through in the output  
MOSFETs.  
25, 26  
BBM1, BBM0  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TP2350B Pin Description  
Pin  
5
Function  
Description  
AGND  
V5  
Analog ground.  
5V power supply input.  
6
7
9
10  
13,17  
14,16  
27,57  
OCD1  
Over-current threshold output (Channel 1)  
This a test pin for the TP2350B. This pin should be left floating.  
Over-current threshold output (Channel 2)  
Non-inverted switching modulator inputs  
Inverted switching modulator inputs  
Bootstrapped voltage to supply drive to gate of high-side FET  
TSS  
OCD2  
Y2, Y1  
Y2B, Y1B  
VBOOT2, VBOOT1  
(Channel 2 & 1)  
30,31  
33,34  
36,48  
37,47  
39,45  
40,44  
41,43  
OCS2LP, OCS2LN  
OCS2HP, OCS2HN  
HO2, HO1  
Over Current Sense inputs, Channel 2 low-side  
Over Current Sense inputs, Channel 2 high-side  
High side gate drive output (Channel 2 & 1)  
HO2COM, HO1COM  
LO2COM, LO1COM  
LO2, LO1  
Kelvin connection to source of high-side transistor (Channel 2 & 1)  
Kelvin connection to source of low-side transistor (Channel 2 & 1)  
Low side gate drive output (Channel 2 & 1)  
VN10  
“Floating” supply input for the FET drive circuitry. This voltage must be stable  
and referenced to VNN.  
42  
50,51  
53,54  
59  
VNN  
OCS1HN, OCS1HP  
OCS1LN ,OCS1LP  
SW-FB  
Negative supply voltage.  
Over Current Sense inputs, Channel 1 high-side  
Over Current Sense inputs, Channel 1 low-side  
Feedback for regulating switching power supply output for VN10  
Switching power supply output for VN10  
Not connected (bonded) internally. Leave these pins floating.  
60  
SMPSO  
NC  
1,2,3,4,8,  
11,12,15,  
18,19,20,  
21,22,23,  
24,25,26,  
28,29,32,  
35,38,46,  
49,52,55,  
56,58,61,  
62,63,64  
Please note that the heatslug on the bottom of the package is connected to VNN.  
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Tripath Technology, Inc. - Technical Information  
Application/Test Circuit  
10 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
External Components Description (Refer to the Application/Test Circuit)  
Components Description  
RI  
RF  
CI  
Inverting input resistance to provide AC gain in conjunction with RF. This input is  
biased at the BIASCAP voltage (approximately 2.5VDC).  
Feedback resistor to set AC gain in conjunction with 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 (2πRICI)  
RFBA  
RFBB  
Feedback divider resistor connected to V5. This resistor is normally set at 1k.  
Feedback divider resistor connected to AGND. This value of this resistor depends  
on the supply voltage setting and helps set the TK2350 gain in conjunction with RI,  
RF, RFBA, and RFBC. Please see the Modulator Feedback Design paragraphs in the  
Application Information Section.  
RFBC  
Feedback resistor connected from either the OUT1(OUT2) to FBKOUT1(FBKOUT2)  
or speaker ground to FBKGND1(FBKGND2). The value of this resistor depends on  
the supply voltage setting and helps set the TK2350 gain in conjunction with RI, RF,  
RFBA,, and RFBB. It should be noted that the resistor from OUT1(OUT2) to  
2
FBKOUT1(FBKOUT2) must have a power rating of greater than  
.
P
= VPP (2RFBC)  
DISS  
Please see the Modulator Feedback Design paragraphs in the Application  
Information Section.  
CFB  
Feedback delay capacitor that both lowers the idle switching frequency and filters  
very high frequency noise from the feedback signal, which improves amplifier  
performance. The value of CFB should be offset between channel 1 and channel 2  
so that the idle switching difference is greater than 40kHz. Please refer to the  
Application / Test Circuit.  
ROFA  
ROFB  
Potentiometer used to manually trim the DC offset on the output of the TK2350.  
Resistor that limits the manual DC offset trim range and allows for more precise  
adjustment.  
RREF  
CA  
Bias resistor. Locate close to pin 15 of the TC2001 and ground at pin 20 of the  
TC2001.  
BIASCAP decoupling capacitor. Should be located close to pin 1 of the TC2001 and  
grounded at pin 20 of the TC2001.  
DB  
Bootstrap diode. This diode charges up the bootstrap capacitors when the output is  
low (at VNN) to drive the high side gate circuitry. A fast or ultra fast recovery diode  
is recommended for the bootstrap circuitry. In addition, the bootstrap diode must be  
able to sustain the entire VPP-VNN voltage. Thus, for most applications, a 150V (or  
greater) diode should be used.  
CB  
High frequency bootstrap capacitor, which filters the high side gate drive supply.  
This capacitor must be located as close to VBOOT1 (pin 57 of the TP2350B) or  
VBOOT2 (pin 27 of the TP2350B) for reliable operation. The “negative” side of CB  
should be connected directly to the HO1COM (pin 47 of the TP2350B) or HO2COM  
(pin 37 of the TP2350B). Please refer to the Application / Test Circuit.  
Bulk bootstrap capacitor that supplements CB during “clipping” events, which result  
in a reduction in the average switching frequency.  
CBAUX  
RB  
Bootstrap resistor that limits CBAUX charging current during TK2350 power up  
(bootstrap supply charging).  
CS  
Supply decoupling for the power supply pins. For optimum performance, these  
components should be located close to the TC2001 and TP2350B and returned to  
their respective ground as shown in the Application/Test Circuit.  
RVNN1  
Main overvoltage and undervoltage sense resistor for the negative supply (VNN).  
Please refer to the Electrical Characteristics Section for the trip points as well as the  
hysteresis band. Also, please refer to the Over / Under-voltage Protection section in  
the Application Information for a detailed discussion of the internal circuit operation  
and external component selection.  
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TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
RVNN2  
RVPP1  
RVPP2  
Secondary overvoltage and undervoltage sense resistor for the negative supply  
(VNN). This resistor accounts for the internal VNNSENSE bias of 1.25V. Nominal  
resistor value should be three times that of RVNN1. Please refer to the Over / Under-  
voltage Protection section in the Application Information for a detailed discussion of  
the internal circuit operation and external component selection.  
Main overvoltage and undervoltage sense resistor for the positive supply (VPP).  
Please refer to the Electrical Characteristics Section for the trip points as well as the  
hysteresis band. Also, please refer to the Over / Under-voltage Protection section in  
the Application Information for a detailed discussion of the internal circuit operation  
and external component selection.  
Secondary overvoltage and undervoltage sense resistor for the positive supply  
(VPP). This resistor accounts for the internal VPPSENSE bias of 2.5V. Nominal  
resistor value should be equal to that of RVPP1. Please refer to the Over / Under-  
voltage Protection section in the Application Information for a detailed discussion of  
the internal circuit operation and external component selection.  
RS  
Over-current sense resistor. Please refer to the section, Setting the Over-current  
Threshold, in the Application Information for a discussion of how to choose the value  
of RS to obtain a specific current limit trip point.  
ROCR  
Over-current “trim” resistor, which, in conjunction with RS, sets the current trip point.  
Please refer to the section, Setting the Over-current Threshold, in the Application  
Information for a discussion of how to calculate the value of ROCR  
.
COCR  
Over-current filter capacitor, which filters the overcurrent signal at the OCR pins to  
account for the half-wave rectified current sense circuit internal to the TC2001. A  
typical value for this component is 220pF. In addition, this component should be  
located near pin 14 or pin 16 of the TC2001 as possible.  
CHBR  
Supply decoupling for the high current Half-bridge supply pins. These components  
must be located as close to the output MOSFETs as possible to minimize output  
ringing which causes power supply overshoot. By reducing overshoot, these  
capacitors maximize both the TP2350B and output MOSFET reliability. These  
capacitors should have good high frequency performance including low ESR and  
low ESL. In addition, the capacitor rating must be twice the maximum VPP voltage.  
Panasonic EB capacitors are ideal for the bulk storage (nominally 33uF) due to their  
high ripple current and high frequency design.  
RG  
DG  
Gate resistor, which is used to control the MOSFET rise/ fall times. This resistor  
serves to dampen the parasitics at the MOSFET gates, which, in turn, minimizes  
ringing and output overshoots. The typical power rating is 1 watt.  
Gate diode, placed in parallel to the gate resistor. This diode will help discharge the  
parasitic capacitance at the MOSFET gates, thus decreasing the MOSFET fall time.  
This helps reduce shoot through current between the top side and bottom side  
output MOSFETs.  
CZ  
RZ  
Zobel capacitor, which in conjunction with RZ, terminates the output filter at high  
frequencies. Use a high quality film capacitor capable of sustaining the ripple current  
caused by the switching outputs.  
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  
power rating is 2 watts.  
LO  
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  
.
LO CO  
fC = 1 (2π LO C O  
)
Q = RL CO  
CO  
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  
and a quality factor of  
)
. Use  
LO CO  
fC = 1 (2π LO C O  
Q = RL CO  
a high quality film capacitor capable of sustaining the ripple current caused by the  
switching outputs.  
DD  
Drain diode. This diode must be connected from the drain of the high side output  
12 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
MOSFET to the drain of the low side output MOSFET. This diode absorbs any high  
frequency overshoots caused by the output inductor LO during high output current  
conditions. In order for this diode to be effective it must be connected directly to the  
drains of both the top and bottom side output MOSFET. An ultra fast recovery diode  
that can sustain the entire VPP-VNN voltage should be used here. In most  
applications a 150V or greater diode must be used.  
DS  
Source diode. This diode must be connected from the source of the high side  
output MOSFET to the source of the low side output MOSFET. This diode absorbs  
any high frequency undershoots caused by the output inductor LO during high output  
current conditions. In order for this diode to be effective it must be connected  
directly to the sources of both the top and bottom sides output MOSFETs. An ultra  
fast recovery diode that can sustain the entire VPP-VNN voltage should be used  
here. In most applications a 150V or greater diode must be used.  
RB  
CB  
Output MOSFET snubber resistor. This resistor forms a low pass filter with CO with  
a frequency of  
. This RC filter removes any high frequency overshoots  
fC = 1 (2πRBCB )  
that can be present on the switching output waveform. This RC filter must be  
connected right across the drain and source of the low side output MOSFET.  
Output MOSFET snubber capacitor. This resistor forms a low pass filter with RB  
with a frequency of  
. This RC filter removes any high frequency  
fC = 1 (2πRBCB )  
overshoots that can be present on the switching output waveform. This RC filter  
must be connected right across the drain and source of the low side output  
MOSFET.  
RS  
Source resistor. This resistor is in series between HOCOM and the source of the  
top side output MOSFET. This resistor serves to limit the voltage swing at the  
HOCOM pin (pins 37 and 47 of the TP2350B) to protect the TP2350B during any  
output overshoots/undershoots. Since this resistor alters the rise and fall times of  
the gate on the high side output MOSFET an additional resistor of the same value is  
placed in series with LOCOM and the source of the bottom side output MOSFET to  
match the rise and fall times of the top side to the bottom side.  
RPG  
Gate resistor for the output MOSFET for the switchmode power supply. Controls  
the rise time, fall time, and reduces ringing for the gate of the output MOSFET for  
the switchmode power supply.  
QB  
Output MOSFET for the switchmode power supply to generate the VN10. This  
output MOSFET must be a P channel device.  
DSW  
LSW  
Flywheel diode for the internal VN10 buck converter. This diode also prevents  
VN10SW from going more than one diode drop negative with respect to VNN.  
VN10 generator filter inductor. This inductor should be sized appropriately so that  
LSW pass 0.5A of current without saturation, and VN10 does not overshoot with  
respect to VNN during TK2350 turn on.  
CSW  
VN10 generator filter capacitors. The high frequency capacitor (0.1uF) must be  
located close to the VN10 pins (pin 41 and 43 of the TP2350B) to maximize device  
performance. The bulk capacitor (100uF) should be sized appropriately such that  
the VN10 voltage does not overshoot with respect to VNN during TK2350 turn on.  
VN10 generator feedback resistor. This resistor sets the nominal VN10 voltage.  
With RSWFB equal to 1k, the VN10 voltage generated will typically be 11V above  
VNN.  
RSWFB  
CSWFB  
VN10 generator feedback capacitor. This capacitor, in conjunction with RSWFB, filters  
the VN10 feedback signal such that the loop is unconditionally stable.  
13 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Typical Performance  
Efficiency versus Output Power  
100  
THD+N versus Output Power  
10  
5
R = 8Ω  
L
f = 1kHz  
90  
BBM = 80nS  
Vs =+28V  
R = 4Ω  
L
80  
70  
60  
50  
BW = 22Hz - 22kHz  
2
1
R = 8Ω  
R = 4Ω  
L
L
0.5  
0.2  
0.1  
40  
f = 1kHz  
30  
20  
10  
0
BBM = 80nS  
Vs =+28V  
0.05  
THD+N =<10%  
0.02  
0.01  
2
5
10  
20  
50  
100  
200  
0
20  
40  
60  
80  
100  
120  
Output Power (W)  
Output Power (W)  
Intermodulation Performance  
Intermodulation Performance  
RL = 4Ω  
RL = 8Ω  
+0  
+0  
-10  
-10  
19kHz, 20kHz, 1:1  
Pout = 40W/Channel  
0dBr = 12.65Vrms  
Vs = +28V  
19kHz, 20kHz, 1:1  
Pout = 20W/Channel  
0dBr = 12.65Vrms  
Vs =+28V  
-20  
-30  
-20  
-30  
BW = 22Hz - 22kHz  
BW = 22Hz - 22kHz  
-40  
-40  
-50  
-50  
-60  
-60  
-70  
-70  
-80  
-80  
-90  
-90  
-100  
-110  
-100  
-110  
-120  
20  
-120  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
Frequency (Hz)  
Frequency (Hz)  
Noise Floor  
Channel Separation versus Frequency  
-70  
-75  
-40  
-45  
V =+28V  
S
BBM = 80nS  
16K FFT  
Pout = 40W/Channel @ 4Ω  
Pout = 20W/Channel @ 8Ω  
VS = +28V  
-50  
Fs = 48kHz  
-80  
-85  
-90  
-95  
-55 BW = 22Hz - 22kHz  
BW = 22Hz - 22kHz  
-60  
-65  
-70  
-75  
-80  
-85  
-90  
-95  
-100  
-105  
-110  
-115  
RL = 4Ω  
RL = 8Ω  
-100  
-105  
-110  
-115  
-120  
-120  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
Frequency (Hz)  
Frequency (Hz)  
14 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Typical Performance  
THD+N versus Frequency versus Break Before Make  
THD+N versus Frequency versus Break Before Make  
RL = 8Ω  
RL = 4Ω  
10  
10  
5
Pout = 20W/Channel  
Vs =+28V  
5
Pout = 40W/Channel  
Vs =+28V  
BW = 22Hz - 22kHz  
BW = 22Hz - 22kHz  
2
1
2
1
0.5  
0.5  
0.2  
0.1  
0.2  
0.1  
BBM = 120nS  
BBM = 120nS  
0.05  
0.05  
0.02  
0.01  
0.02  
0.01  
BBM = 80nS  
BBM = 80nS  
2k  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
20  
50  
100  
200  
500  
1k  
5k  
10k  
20k  
Frequency (Hz)  
Frequency (Hz)  
THD+N versus Frequency versus Bandwidth  
THD+N versus Frequency versus Bandwidth  
RL = 4Ω  
RL = 8Ω  
10  
5
10  
5
Pout = 40W/Channel  
Vs =+28V  
Pout = 20W/Channel  
Vs =+28V  
BBM = 80nS  
BBM = 80nS  
2
1
2
1
0.5  
0.5  
0.2  
0.1  
0.2  
0.1  
BW = 30kHz  
BW = 22kHz  
0.05  
0.05  
BW = 30kHz  
0.02  
0.01  
0.02  
0.01  
BW = 22kHz  
100 200  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
20  
50  
500  
1k  
2k  
5k  
10k  
20k  
Frequency (Hz)  
Frequency (Hz)  
THD+N versus Output Power versus Supply Voltage  
THD+N versus Output Power versus Supply Voltage  
R = 4Ω  
R = 8Ω  
L
L
10  
5
10  
5
f = 1kHz  
f = 1kHz  
BBM = 80nS  
BBM = 80nS  
BW = 22Hz - 22kHz  
BW = 22Hz - 22kHz  
2
1
2
1
23V  
28V  
35V  
23V  
28V  
35V  
0.5  
0.5  
0.2  
0.1  
0.2  
0.1  
0.05  
0.05  
0.02  
0.02  
0.01  
0.01  
1
2
5
10  
20  
50  
100  
200  
2
5
10  
20  
50  
100  
200  
Output Power (W)  
Output Power (W)  
15 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Typical Performance  
Efficiency versus Output Power  
THD+N versus Output Power  
100  
10  
5
RL = 8Ω  
f = 1kHz  
BBM = 80nS  
Vs =+45V  
RL = 4Ω  
BW = 22Hz - 22kHz  
80  
2
1
R = 8Ω  
R = 4Ω  
L
L
60  
0.5  
0.2  
0.1  
40  
f = 1kHz  
0.05  
BBM = 80nS  
20  
Vs =+45V  
THD+N<10%  
0.02  
0.01  
0
0
50  
100  
150  
200  
250  
300  
2
5
10  
20  
50  
100  
200  
500  
Output Power (W)  
Output Power (W)  
Intermodulation Performance  
Intermodulation Performance  
L = 4Ω  
RL = 8Ω  
R
+0  
+0  
19kHz, 20kHz, 1:1  
Pout = 30W/Channel  
0dBr = 15.5Vrms  
Vs =+45V  
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
-110  
19kHz, 20kHz, 1:1  
Pout = 60W/Channel  
0dBr = 15.5Vrms  
Vs = +45V  
-10  
-20  
-30  
BW = 22Hz - 22kHz  
BW = 22Hz - 22kHz  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
-110  
-120  
-120  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
Frequency (Hz)  
Frequency (Hz)  
Noise Floor  
Channel Separation versus Frequency  
-70  
-75  
-40  
-45  
VS = +/-45V  
BBM = 80nS  
16kFFT  
Pout = 60W/Channel @ 4Ω  
Pout = 30W/Channel @ 8Ω  
VS = +45V  
-50  
-55  
FS = 48kHz  
BW = 22Hz - 22kHz  
-80 BW = 22Hz-22kHz  
-60  
-85  
-90  
-65  
-70  
-75  
-95  
-80  
-85  
RL = 4Ω  
RL = 8Ω  
-100  
105  
-90  
-95  
-100  
-105  
-110  
-115  
-110  
-115  
-120  
-120  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
10k  
20  
50  
100  
200  
500  
1k  
2k  
5k  
20k  
Frequency (Hz)  
Frequency (Hz)  
16 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Typical Performance  
THD+N versus Frequency versus Break Before Make  
THD+N versus Frequency versus Break Before Make  
RL = 4Ω  
RL = 8Ω  
10  
5
10  
Pout = 30W/Channel  
Pout = 60W/Channel  
Vs =+45V  
Vs =+45V  
5
BW = 20Hz - 22kHz  
BW = 22Hz - 22kHz  
2
1
2
1
0.5  
0.5  
0.2  
0.1  
0.2  
BBM = 120nS  
BBM = 120nS  
0.1  
0.05  
0.05  
BBM = 80nS  
0.02  
0.01  
0.02  
BBM = 80nS  
5k  
0.01  
20  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
50  
100  
200  
500  
1k  
2k  
10k  
20k  
Frequency (Hz)  
Frequency (Hz)  
THD+N versus Frequency versus Bandwidth  
RL = 4Ω  
THD+N versus Frequency versus Bandwidth  
10  
5
RL = 8Ω  
10  
Pout = 60W/Channel  
Vs =+45V  
Pout = 30W/Channel  
Vs =+45V  
BBM = 80nS  
5
BBM = 80nS  
2
1
2
1
0.5  
0.5  
0.2  
0.1  
0.2  
0.1  
BW = 30kHz  
BW = 22kHz  
BW = 30kHz  
BW = 22kHz  
0.05  
0.05  
0.02  
0.01  
0.02  
0.01  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
Frequency (Hz)  
20  
50  
100  
200  
500  
1k  
2k  
5k  
10k  
20k  
Frequency (Hz)  
THD+N versus Output Power versus Supply Voltage  
THD+N versus Output Power versus Supply Voltage  
R = 4Ω  
R = 8Ω  
L
L
10  
5
10  
5
f = 1kHz  
f = 1kHz  
BBM = 80nS  
BW = 22Hz - 22kHz  
BBM = 80nS  
BW = 22Hz - 22kHz  
2
1
2
1
39V  
45V  
54V  
39V  
54V  
45V  
0.5  
0.5  
0.2  
0.1  
0.2  
0.1  
0.05  
0.05  
0.02  
0.02  
0.01  
0.01  
1
2
5
10  
20  
50  
100  
200  
500  
2
5
10  
20  
50  
100  
200  
500  
Output Power (W)  
Output Power (W)  
17 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Application Information  
Figure 1 is a simplified diagram of one channel (Channel 1) of a TK2350 amplifier to assist in  
understanding its operation.  
TC2001  
TP2350B  
BBM0 26  
51 OCS1HP  
VPP  
BBM1  
25  
22  
OVER  
DB  
CS  
CURRENT  
DETECTION  
RS  
OAOUT1  
VN10  
RB  
OCS1HN  
50  
57 VBOOT1  
RI  
RF  
CI  
V5  
QO  
RG  
RG  
INV1 23  
ROFB  
+
+
CB  
0.1uF  
-
Y1  
9
17  
16  
48 HO1  
47 HO1COM  
CBAUX  
+
CHBR  
AGND  
V5  
VN10  
OUTPUT  
FILTER  
QO  
RS  
Processing  
&
Modulation  
ROFB  
10  
Y1B  
44 LO1  
RL  
ROFA  
45  
LO1COM  
COF  
2.5V  
V5  
54 OCS1LP  
Offset Trim  
Circuit  
OVER  
CURRENT  
DETECTION  
CA  
5V  
53 OCS1LN  
BIASCAP  
1
VNN  
41,43  
VN10  
VN10  
CS  
CSW  
VNN  
VNN  
42  
6
MUTE 24  
REF 15  
OCR1  
7
VNN  
V5  
5V  
CS  
5
AGND  
RREF  
RVNN1  
16  
OCR1  
COCR  
VNNSENSE 17  
V5  
VNN  
VPP  
OVER/  
OVER  
CURRENT  
DETECTION  
UNDER  
VOLTAGE  
DETECTION  
ROCR  
RVPP1  
VPPSENSE  
19  
RFBA  
RFBA  
RFBC  
RVNN2  
RVPP1  
6
7
FBKOUT1  
FBKGND1  
V5  
V5  
RFBC  
CFB  
V5  
21  
RFBB  
RFBB  
5V  
CS  
HMUTE  
8
AGND 20  
Analog Ground  
Power Ground  
F. BEAD  
Figure 1: Simplified TK2350 Amplifier  
TK2350 Basic Amplifier Operation  
The audio input signal is fed to the processor internal to the TC2001, where a switching pattern is  
generated. The average idle (no input) switching frequency is approximately 700kHz. With an  
input signal, the pattern is spread spectrum and varies between approximately 200kHz and  
1.5MHz depending on input signal level and frequency. Complementary copies of the switching  
pattern is output through the Y1 and Y1B pins on the TC2001. These switching patterns are input  
to the TP230 where they are level-shifted by the MOSFET drivers and then output to the gates  
(HO1 and LO1) of external 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 VPP  
and VNN. This signal is then low-pass filtered to obtain an amplified reproduction of the audio  
input signal.  
The TC2001 processor is operated from a 5-volt supply. In the generation of the switching  
patterns for the output MOSFETs, the processor inserts a “break-before-make” dead time between  
the turn-off of one transistor and the turn-on of the other in order to minimize shoot-through  
currents in the external MOSFETs. The dead time can be programmed by setting the break-  
before-make control bits, BBM1 and BBM0. Feedback information from the output of the half-  
bridge is supplied to the processor via FBKOUT1. Additional feedback information to account for  
ground bounce is supplied via FBKGND1.  
18 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
The MOSFET drivers in the TP2350B are operated from voltages obtained from VN10 and  
LO1COM for the low-side driver, and VBOOT1 and HO1COM for the high-side driver. VN10 must  
be a regulated 10V above VNN.  
N-Channel MOSFETs are used for both the top and bottom of the half bridge. The gate resistors,  
RG, are used to control MOSFET slew rate and thereby minimize voltage overshoots.  
Circuit Board Layout  
The TK2350 is a power (high current) amplifier that operates at relatively high switching  
frequencies. The output of the amplifier switches between VPP and VNN at high speeds while  
driving large currents. This high-frequency digital signal is passed through an LC low-pass 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 TK2350 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. Please refer to the TK2350 evaluation board  
document, RB-TK2350, available on the Tripath website, at www.tripath.com.  
The following components are important to place near either their associated TK2350 or output  
MOSFET pins. The recommendations are ranked in order of layout importance, either for proper  
device operation or performance considerations.  
-
The capacitors, CHBR, provide high frequency bypassing of the amplifier power supplies  
and will serve to reduce spikes across the supply rails. Please note that both mosfet  
half-bridges must be decoupled separately. In addition, the voltage rating for CHBR  
should be at least 150V as this capacitor is exposed to the full supply range, VPP-VNN.  
-
CFB removes very high frequency components from the amplifier feedback signals and  
lowers the output switching frequency by delaying the feedback signals. In addition, the  
value of CFB is different for channel 1 and channel 2 to keep the average switching  
frequency difference greater than 40kHz. This minimizes in-band audio noise. Locate  
these capacitors as close to their respective TC2001 pin as possible.  
-
-
To minimize noise pickup and minimize THD+N, RFBC should be located as close to the  
TC2001 as possible. Make sure that the routing of the high voltage feedback lines is  
kept far away from the input op amps or significant noise coupling may occur. It is best  
to shield the high voltage feedback lines by using a ground plane around these traces  
as well as the input section. The feedback and feedback ground traces should be  
routed together in parallel.  
CB, CSW provides high frequency bypassing for the VN10 and bootstrap supplies. Very  
high currents are present on these supplies.  
In general, to enable placement as close to the TK2350, and minimize PCB parasitics, the  
capacitors CFB, CB and CSW should be surface mount types, located on the “solder” side of the  
board.  
19 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
Some components are not sensitive to location but are very sensitive to layout and trace routing.  
-
To maximize the damping factor and reduce distortion and noise, the modulator  
feedback connections should be routed directly to the pins of the output inductors. LO.  
Please refer to the RB-TK2350 for more information.  
-
-
The output filter capacitor, CO, and zobel capacitor, CZ, should be star connected with  
the load return. The output ground feedback signal should be taken from this star point.  
The modulator feedback resistors, RFBA and RFBB, should all be grounded and attached  
to 5V together. These connections will serve to minimize common mode noise via the  
differential feedback. Please refer to the RB-TK2350 evaluation board for more  
information.  
-
-
The feedback signals that come directly from the output inductors are high voltage and  
high frequency in nature. If they are routed close to the input nodes, INV1 and INV2, the  
high impedance inverting opamp pins will pick up noise. This coupling will result in  
significant background noise, especially when the input is AC coupled to ground, or an  
external source such as a CD player or signal generator is connected. Thus, care  
should be taken such that the feedback lines are not routed near any of the input  
section.  
To minimize the possibility of any noise pickup, the trace lengths of INV1 and INV2  
should be kept as short as possible. This is most easily accomplished by locating the  
input resistors, RI and the input stage feedback resistors, RF as close to the TC2001 as  
possible. In addition, the offset trim resistor, ROFB, which connects to either INV1, or  
INV2, should be located close to the TC2001 input section.  
TK2350 Grounding  
Proper grounding techniques are required to maximize TK2350 functionality and performance.  
Parametric parameters such as THD+N, Noise Floor and Crosstalk can be adversely affected if  
proper grounding techniques are not implemented on the PCB layout. The following discussion  
highlights some recommendations about grounding both with respect to the TK2350 as well as  
general “audio system” design rules.  
The TK2350 is divided into three sections: the input section, which is the TC2001, the MOSFET  
driver section, which is the TP2350B, and the output (high voltage) section, which is the output  
MOSFETs. On the TK2350 evaluation board, the ground is also divided into distinct sections, one  
for the input and the MOSFET driver, and another one for the output. To minimize ground loops  
and keep the audio noise floor as low as possible, the two grounds must be only connected at a  
single point. Depending on the system design, the single point connection may be in the form of a  
ferrite bead or a PCB trace.  
The analog grounds, must be connected to pin 20 on the TC2001 and pin 5 on the TP2350B. The  
ground for the V5 power supply should connect directly to pin 20 of the TC2001. Additionally, any  
external input circuitry such as preamps, or active filters, should be referenced to pin 20 on the  
TC2001.  
For the power section, Tripath has traditionally used a “star” grounding scheme. Thus, the load  
ground returns and the power supply decoupling traces are routed separately back to the power  
supply. In addition, any type of shield or chassis connection would be connected directly to the  
ground star located at the power supply. These precautions will both minimize audible noise and  
enhance the crosstalk performance of the TK2350.  
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The TC2001 incorporates a differential feedback system to minimize the effects of ground bounce  
and cancel out common mode ground noise. As such, the feedback from the output ground for  
each channel needs to be properly sensed. This can be accomplished by connecting the output  
ground “sensing” trace directly to the star formed by the output ground return, output capacitor,  
CO, and the zobel capacitor, CZ. Refer to the Application / Test Circuit for a schematic description.  
TK2350 Amplifier Gain  
The gain of the TK2350 is the product of the input stage gain and the modulator gain for the  
TC2001. Please refer to the sections, Input Stage Design, and Modulator Feedback Design, for a  
complete explanation of how to determine the external component values.  
A
A
VTK2350 = AVINPUTSTAG  
E
* AV MODULATOR  
R
F
R
FBC * (RFBA + RFBB )  
VTK2350 ≈ −  
+ 1  
R
I
R
FBA * RFBB  
For example, using a TC2001 with the following external components,  
RI = 20kΩ  
RF = 20kΩ  
R
FBA = 1kΩ  
RFBB = 1.07kΩ  
RFBC = 13.3kΩ  
20k 13.3k * (1.0k + 1.07k )  
V
V
A
VTK2350 ≈ −  
+ 1 = - 10.71  
49.9k Ω  
1.0k * 1.07k Ω  
Input Stage Design  
The TC2001 input stage is configured as an inverting amplifier, allowing the system designer  
flexibility in setting the input stage gain and frequency response. Figure 2 shows a typical  
application where the input stage is a constant gain inverting amplifier. The input stage gain  
should be set so that the maximum input signal level will drive the input stage output to 4Vpp.  
The gain of the input stage, above the low frequency high pass filter point, is that of a simple  
inverting amplifier:  
R
F
A
VINPUTSTAG E = −  
R
I
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Tripath Technology, Inc. - Technical Information  
TC2001  
OAOUT1  
22  
V5  
CI  
RI  
RF  
INV1 23  
+
-
+
INPUT1  
AGND  
BIASCAP  
V5  
CI  
RI  
+
-
28  
27  
INV2  
+
RF  
INPUT2  
AGND  
OAOUT2  
Figure 2: TC2001 Input Stage  
Input Capacitor Selection  
CIN can be calculated once a value for RIN has been determined. CIN and RIN determine the input  
low-frequency pole. Typically this pole is set at 10Hz. CIN is calculated according to:  
CIN = 1 / (2π x FP x RIN)  
where: RIN = Input resistor value in ohms  
FP = Input low frequency pole (typically 10Hz)  
Modulator Feedback Design  
The modulator converts the signal from the input stage to the high-voltage output signal. The  
optimum gain of the modulator is determined from the maximum allowable feedback level for the  
modulator and maximum supply voltages for the power stage. Depending on the maximum supply  
voltage, the feedback ratio will need to be adjusted to maximize performance. The values of RFBA  
,
RFBB and RFBC (see explanation below) define the gain of the modulator. Once these values are  
chosen, based on the maximum supply voltage, the gain of the modulator will be fixed even with  
as the supply voltage fluctuates due to current draw.  
For the best signal-to-noise ratio and lowest distortion, the maximum modulator feedback voltage  
should be approximately 4Vpp. This will keep the gain of the modulator as low as possible and  
still allow headroom so that the feedback signal does not clip the modulator feedback stage.  
Figure 3 shows how the feedback from the output of the amplifier is returned to the input of the  
modulator. The input to the modulator (FBKOUT1/FBKGND1 for channel 1) can be viewed as  
inputs to an inverting differential amplifier. RFBA and RFBB bias the feedback signal to approximately  
2.5V and RFBC scales the large OUT1/OUT2 signal to down to 4Vpp.  
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Tripath Technology, Inc. - Technical Information  
1/2 TC2001  
V5  
RFBA  
RFBA  
RFBC  
FBKOUT1  
Processing  
&
Modulation  
28  
27  
OUT1  
FBKGND1  
OUT1 GROUND  
RFBC  
RFBB  
RFBB  
AGND  
Figure 3: Modulator Feedback  
The modulator feedback resistors are:  
R
R
FBA = User specified, typically 1KΩ  
R
FBA * VPP  
FBB  
=
(VPP - 4)  
R
FBA * VPP  
R
A
FBC  
=
4
R
FBC * (RFBA + RFBB )  
V - MODULATOR  
+ 1  
R
FBA * RFBB  
The above equations assume that VPP=|VNN|.  
For example, in a system with VPPMAX=52V and VNNMAX=-52V,  
R
FBA = 1k, 1%  
RFBB = 1.08k, use 1.07k, 1%  
RFBC = 13.0k, use 13.3k, 1%  
The resultant modulator gain is:  
13.3k * (1.0k + 1.07k )  
A
V - MODULATOR  
+ 1 = 26.73V/V  
1.0k * 1.07k Ω  
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Mute  
When a logic high signal is supplied to MUTE, both amplifier channels are muted (both high- and  
low-side transistors are turned off). When a logic level low is supplied to MUTE, both amplifiers  
are fully operational. There is a delay of approximately 200 milliseconds between the de-assertion  
of MUTE and the un-muting of the TK2350.  
Turn-on & Turn-off Noise  
If turn-on or turn-off noise is present in a TK2350 amplifier, the cause is frequently due to other  
circuitry external to the TK2350. While the TK2350 has circuitry to suppress turn-on and turn-off  
transients, the combination of the power supply and other audio circuitry with the TK2350 in a  
particular application may exhibit audible transients. One solution 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 TK2350 would need to be  
implemented to detect these failures.  
DC Offset  
While the DC offset voltages that appear at the speaker terminals of a TK2350 amplifier are  
typically small, Tripath recommends that any offsets during operation be nulled out of the amplifier  
with a circuit like the one shown connected to IN1 and IN2 in the Test/Application Circuit.  
It should be noted that the DC voltage on the output of a TK2350 amplifier with no load in mute will  
not be zero. This offset does not need to be nulled. The output impedance of the amplifier in  
mute mode is approximately 10K. This means that the DC voltage drops to essentially zero  
when a typical load is connected.  
HMUTE  
The HMUTE pin on the TC2001 is a 5V logic output that indicates various fault conditions within  
the device. These conditions include: over-current, overvoltage and undervoltage. The HMUTE  
output is capable of directly driving an LED through a series 2kresistor.  
Over-current Protection  
The TK2350 has over-current protection circuitry to protect itself and the output transistors from  
short-circuit conditions. The TK2350 uses the voltage across a resistor RS (measured via  
OCS1HP, OCS1HN, OCS1LP and OCS1LN of the TP2350B) that is in series with each output  
MOSFET to detect an over-current condition. RS and ROCR are used to set the over-current  
threshold. The OCS pins must be Kelvin connected for proper operation. See “Circuit Board  
Layout” in Application Information for details.  
When the voltage across ROCR becomes greater than VTOC (typically 0.97V) the TC2001 will shut  
off the output stages of its amplifiers. The occurrence of an over-current condition is latched in the  
TK2350 and can be cleared by toggling the MUTE input or cycling power.  
Setting Over-current Threshold  
RS and ROCR determine the value of the over-current threshold, ISC:  
ISC = 3580 x (VTOC – IBIAS * ROCR)/(R OCR * RS)  
R
OCR = (3580 x VTOC)/(ISC * RS+3580 * IBIAS  
)
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where:  
RS and ROCR are in Ω  
VTOC = Over-current sense threshold voltage (See Electrical Characteristics Table)  
= 0.97V typically  
IBIAS = 20uA  
For example, to set an ISC of 30A, ROCR = 9.63Kand RS will be 10m.  
As high-wattage resistors are usually only available in a few low-resistance values (10m, 25mΩ  
and 50m), ROCR can be used to adjust for a particular over-current threshold using one of these  
values for RS.  
It should be noted that the addition of the bulk CHBR capacitor shown in the Application / Test  
Diagram will increase the ISC level. Thus, it will be larger than the theoretical value shown above.  
Once the designer has settled on a layout and specific CHBR value, the system ISC trip point can be  
adjusted by increasing the ROCR value. The ROCR should be increased to a level that allows  
expected range of loads to be driven well into clipping without current limiting while still protecting  
the output MOSFETs in case of a short circuit condition.  
Auto Recovery Circuit for Overcurrent Fault Condition  
If an overcurrent fault condition occurs the HMUTE pin (pin 8 of the TC2001) will be latched high  
and the amplifier will be muted. The amplifier will remain muted until the MUTE pin (pin 24 of the  
TC2001) is toggled high and then low or the power supplies are turned off and then on again. The  
circuit shown below in Figure 4 is a circuit that will detect if HMUTE is high and then toggle the  
mute pin high and then low, thus resetting the amplifier. The LED, D1 will turn on when HMUTE is  
high. The reset time has been set for approximately 2.5 seconds. The duration of the reset time  
is controlled by the RC time constant set by R306 and C311. To increase the reset, time increase  
the value of C311. To reduce the reset time, reduce the value of C311. Please note that this  
circuit is optional and is not included on the RB-TK2350-X evaluation boards.  
V5  
R309  
1k, 5%  
D1  
LED  
R311  
R306  
510k, 5%  
R307  
10k, 5%  
R308  
10k, 5%  
Q305  
2N3906  
1k, 5%  
R311  
1k, 5%  
MUTE  
Pin 24  
C311  
10uF, NP  
Q302  
2N3904  
Q303  
2N7002  
R311  
1k, 5%  
Jumper  
HMUTE  
Pin 8  
Q304  
2N3904  
R310  
1k, 5%  
remove jumper to  
enable mute  
AGND  
Figure 4: Overcurrent Autorecovery Circuit  
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Over- and Under-Voltage Protection  
The TC2001 senses the power rails through external resistor networks connected to VNNSENSE  
and VPPSENSE. The over- and under-voltage limits are determined by the values of the resistors  
in the networks, as described in the table “Test/Application Circuit Component Values”. If the  
supply voltage falls outside the upper and lower limits determined by the resistor networks, the  
TC2001 shuts off the output stages of the amplifiers. The removal of the over-voltage or under-  
voltage condition returns the TK2350 to normal operation. Please note that trip points specified in  
the Electrical Characteristics table are at 25°C and may change over temperature.  
The TC2001 has built-in over and under voltage protection for both the VPP and VNN supply rails.  
The nominal operating voltage will typically be chosen as the supply “center point.” This allows  
the supply voltage to fluctuate, both above and below, the nominal supply voltage.  
VPPSENSE (pin 19) performs the over and undervoltage sensing for the positive supply, VPP.  
VNNSENSE (pin 17) performs the same function for the negative rail, VNN. When the current  
through RVPPSENSE (or RVNNSENSE) goes below or above the values shown in the Electrical  
Characteristics section (caused by changing the power supply voltage), the TK2350 will be muted.  
VPPSENSE is internally biased at 2.5V and VNNSENSE is biased at 1.25V.  
Once the supply comes back into the supply voltage operating range (as defined by the supply  
sense resistors), the TK2350 will automatically be unmuted and will begin to amplify. There is a  
hysteresis range on both the VPPSENSE and VNNSENSE pins. If the amplifier is powered up in  
the hysteresis band the TK2350 will be muted. Thus, the usable supply range is the difference  
between the over-voltage turn-off and under-voltage turn-off for both the VPP and VNN supplies. It  
should be noted that there is a timer of approximately 200mS with respect to the over and under  
voltage sensing circuit. Thus, the supply voltage must be outside of the user defined supply range  
for greater than 200mS for the TK2350 to be muted.  
Figure 5 shows the proper connection for the Over / Under voltage sense circuit for both the  
VPPSENSE and VNNSENSE pins.  
V5  
VNN  
TC2001  
RVNN2  
RVNN1  
17  
19  
VNNSENSE  
V5  
VPP  
RVPP2  
RVPP1  
VPPSENSE  
Figure 5: Over / Under voltage sense circuit  
The equation for calculating RVPP1 is as follows:  
VPP  
VPPSENSE  
R
VPP1 =  
I
Set RVPP2 = RVPP1 .  
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The equation for calculating RVNNSENSE is as follows:  
VNN  
R
VNN1 =  
I
VNNSENSE  
Set  
.
R
VNN2 = 3 × RVNN1  
IVPPSENSE or IVNNSENSE can be any of the currents shown in the Electrical Characteristics  
table for VPPSENSE and VNNSENSE, respectively.  
The two resistors, RVPP2 and RVNN2 compensate for the internal bias points. Thus, RVPP1 and RVNN1  
can be used for the direct calculation of the actual VPP and VNN trip voltages without considering  
the effect of RVPP2 and RVNN2  
.
Using the resistor values from above, the actual minimum over voltage turn off points will be:  
VPP MIN_OV_TUR N_OFF = RVPP1 × IVPPSENSE (MIN_OV_TU RN_OFF)  
VNN MIN_OV_TUR N_OFF = −(RVNN1 × IVNNSENSE (MIN_OV_TU RN_OFF)  
)
The other three trip points can be calculated using the same formula but inserting the appropriate  
IVPPSENSE (or IVNNSENSE) current value. As stated earlier, the usable supply range is the difference  
between the minimum overvoltage turn off and maximum under voltage turn-off for both the VPP  
and VNN supplies.  
VPP RANGE = VPP MIN_OV_TUR N_OFF - VPP MAX_UV_TUR N_OFF  
VNN RANGE = VNN MIN_OV_TUR N_OFF - VNN MAX_UV_TUR N_OFF  
VN10 Supply and Switch Mode Power Supply Controller  
VN10 is an additional supply voltage required by the TP2350B. VN10 must be 10 volts more  
positive than the nominal VNN. VN10 must track VNN. Generating the VN10 supply requires  
some care.  
The proper way to generate the voltage for VN10 is to use a 10V-postive supply voltage  
referenced to the VNN supply. The TP2350B has an internal switch mode power supply controller  
which generates the necessary floating power supply for the MOSFET driver stage in the  
TP2350B (nominally 11V with the external components shown in Application / Test Circuit). The  
SMPSO pin (pin 60) provides a switching output waveform to drive the gate of a P channel  
MOSFET. The source of the P channel MOSFET should be tied to power ground and the drain of  
the MOSFET should be tied to the VN10 through a 100uH inductor. The performance curves  
shown in this datasheet as well as the efficiency measurements were done using the internal  
VN10 generator. Tripath recommends using the internal VN10 generator to power the TP2350B.  
Figure 6 shows how the VN10 generator should be connected.  
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TP2350B  
RSW FB 1kΩ  
59 SW-FB  
CSW FB  
0.1uF  
VN10  
Switchmode  
Power Supply  
LSW  
QP  
VNN  
RPG 10Ω  
100uH  
60  
SMPSO  
VN10  
+
DSW  
B1100DICT  
CSW  
0.1uF  
CSW  
100uF  
VNN  
Figure 6: VN10 Generator  
In some cases, though, a designer may wish to use an external VN10 generator. The  
specification for VN10 quiescent current (200mA typical, 250mA maximum) in the Electrical  
Characteristics section states the amount of current needed when an external floating supply is  
used. If the internal VN10 generator is not used, Tripath recommends shorting SMPSO(pin 60) to  
VNN(pin 42) and SW-FB(pin 59) to VNN(pin 42).  
One apparent method to generate the VN10 supply voltage is to use a negative IC regulator to  
drop PGND down to 10V (relative to VNN). This method will not work since negative regulators  
only sink current into the regulator output and will not be capable of sourcing the current required  
by VN10. Furthermore, problems can arise since VN10 will not track movements in VNN. The  
external VN10 supply must be able to source a maximum of 250mA into the VN10 pin. Thus, a  
positive supply must be used and must be referenced to the VNN rail. If the external VN10 supply  
does not track fluctuations in the VNN supply or is not able to source current into the VN10 pin, the  
TP2350B will not work and can also become permanently damaged.  
Figure 7 shows the correct way to power the TK2350:  
VPP  
V5  
VPP  
5V  
AGND  
VN10  
PGND  
VNN  
10V  
VNN  
F. BEAD  
Figure 7: Proper Power Supply Connection  
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Output Transistor Selection  
The key parameters to consider when selecting what MOSFET to use with the TK2350 are drain-  
source breakdown voltage (BVdss), gate charge (Qg), and on-resistance (RDS(ON)).  
The BVdss rating of the MOSFET needs to be selected to accommodate the voltage swing  
between VSPOS and VSNEG as well as any voltage peaks caused by voltage ringing due to switching  
transients. With a ‘good’ circuit board layout, a BVdss that is 50% higher than the VPP and VNN  
voltage swing is a reasonable starting point. The BVdss rating should be verified by measuring  
the actual voltages experienced by the MOSFET in the final circuit.  
Ideally a low Qg (total gate charge) and low RDS(ON) are desired for the best amplifier performance.  
Unfortunately, these are conflicting requirements since RDS(ON) is inversely proportional to Qg for a  
typical MOSFET. The design trade-off is one of cost versus performance. A lower RDS(ON) means  
lower I2RDS(ON) losses but the associated higher Qg translates into higher switching losses (losses  
= Qg x 10 x 1.2MHz). A lower RDS(ON) also means a larger silicon die and higher cost. A higher  
R
DS(ON) means lower cost and lower switching losses but higher I2RDSON losses.  
The following table lists BVdss, Qg and RDS(ON) for MOSFETs that Tripath has used with the  
TK2350:  
Manufacturer  
Manufacturer’s  
Part Number  
STW34NB20  
STP19NB20  
IRFB41N15D  
IRFB31N20D  
FQA34N20  
BVdss  
Qg  
RDS(ON) (Max)  
(Ohms)  
0.075  
(nanoCoulombs)  
ST Microelectronics  
ST Microelectronics  
International Rectifier  
International Rectifier  
Fairchild  
200  
200  
150  
200  
200  
60  
29  
67  
70  
60  
0.18  
0.045  
0.082  
0.075  
Gate Resistor Selection  
The gate resistors, RG, are used to control MOSFET switching rise/fall times and thereby minimize  
voltage overshoots. They also dissipate a portion of the power resulting from moving the gate  
charge each time the MOSFET is switched. If RG is too small, excessive heat can be generated in  
the driver. Large gate resistors lead to slower MOSFET switching, which requires a larger break-  
before-make (BBM) delay.  
Break-Before-Make (BBM) Timing Control  
The half-bridge power MOSFETs require a deadtime between when one transistor is turned off  
and the other is turned on (break-before-make) in order to minimize shoot through currents. The  
TC2001 has BBM0 and BBM1 that are logic inputs (connected to logic high or pulled down to logic  
low) that control the break-before-make timing of the output transistors according to the following  
table.  
BBM1  
BBM0  
Delay  
120 ns  
80 ns  
40 ns  
0 ns  
0
0
1
1
0
1
0
1
Table 1: BBM Delay  
The tradeoff involved in making this setting is that as the delay is reduced, distortion levels  
improve but shoot-through and power dissipation increase. Both the 40nS and 0nS settings are  
NOT recommended due the high level of shoot-thru current that will result. Thus, BBM1 should be  
grounded in most applications. All typical curves and performance information was done with  
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using the 80ns or 120ns BBM setting. The actual amount of BBM required is dependent upon  
other component values and circuit board layout, the value selected should be verified in the  
actual application circuit/board. It should also be verified under maximum temperature and power  
conditions since shoot-through in the output MOSFETs can increase under these conditions,  
possibly requiring a higher BBM setting than at room temperature.  
Output Filter Design  
One advantage of Tripath amplifiers over PWM solutions is the ability to use higher-cutoff-  
frequency filters. This means 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, 100kHz LC filter. Tripath has obtained  
good results with LF = 11uH and CF = 0.22uF.  
The core material of the output filter inductor has an effect on the distortion levels produced by a  
TK2350 amplifier. Tripath recommends low-mu type-2 iron powder cores because of their low  
loss and high linearity (available from Micrometals, www.micrometals.com). The specific core  
used on the RB-TK2350 was a T106-2 wound with 29 turns of 16AWG wire.  
Tripath also recommends that an RC damper be used after the LC low-pass filter. No-load  
operation of a TK2350 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 RD =  
20and CD = 0.22uF.  
Bridging the TK2350  
The TK2350 can be bridged by returning the signal from VP1 to the input resistor at INV2. OUT1  
will then be a gained version of VP1, and OUT2 will be a gained and inverted version of OAOUT1  
(see Figure 8). When the two amplifier outputs are bridged, the apparent load impedance seen by  
each output is halved, so the current capability of the output MOSFETs, as well their power  
dissipation capability, must be accounted for in the design. In addition, the higher peak currents  
caused by driving lower impedance loads will cause additional ringing on the outputs. Thus, the  
layout and supply decoupling for low impedance (below 8 ohms) bridged applications must be  
extremely good to minimize output ringing and to ensure proper amplifier performance.  
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TC2001  
OAOUT1  
22  
V5  
CI  
RI  
RF  
INV1 23  
+
-
+
INPUT1  
AGND  
BIASCAP  
V5  
20k  
20k  
+
-
INV2 28  
AGND  
OAOUT2  
27  
Figure 8: Input Stage Setup for Bridging  
The switching outputs, OUT1 and OUT2, are not synchronized, so a common inductor may not be  
used with a bridged TK2350. For this same reason, individual zobel networks must be applied to  
each output to load each output and lower the Q of each common mode differential LC filter.  
Low-frequency Power Supply Pumping  
A potentially troublesome phenomenon in single-ended switching amplifiers is power supply  
pumping. This phenomenon 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 in magnitude) 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. If a DC offset on the order of 0.3V  
is allowed to develop on the output of the amplifier (see “DC Offset Adjust”), the supplies can be  
boosted to the point where the amplifier’s over-voltage protection triggers.  
One solution to the pumping issue it to use large power supply capacitors to absorb the pumped  
supply current without significant voltage boost. The low-frequency pole used at the input to the  
amplifier determines the value of the capacitor required. This works for AC signals only.  
A no-cost solution to the pumping problem uses the fact that music has low frequency information  
that is correlated in both channels (it is in phase). This information can be used to eliminate boost  
by putting the two channels of a TK2350 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.  
Theoretical Efficiency Of A TK2350 Amplifier  
The efficiency, η, of an amplifier is:  
η = POUT/PIN  
31 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
The power dissipation of a TK2350 amplifier is primarily determined by the on resistance, RON, of  
the output transistors used, and the switching losses of these transistors, PSW. For a TK2350  
amplifier, PIN (per channel) is approximated by:  
PIN = PDRIVER + PSW + POUT ((RS + RON + RCOIL + RL)/RL)2  
where: PDRIVER = Power dissipated in the TA3020 = 1.6W/channel  
PSW = 2 x (0.01) x Qg (Qg is the gate charge of M, in nano-coulombs)  
RCOIL = Resistance of the output filter inductor (typically around 50m)  
For a 125W RMS per channel, 8load amplifier using STW34NB20 MOSFETs, and an RS of  
50m,  
PIN = PDRIVER + PSW + POUT ((RS + RON + RCOIL + RL)/RL)2  
= 1.6 + 2 x (0.01) x (95) + 125 x ((0.025 + 0.11 + 0.05 + 8)/8)2 = 1.6 + 1.9 + 130.8  
= 134.3W  
In the above calculation the RDS (ON) of 0.065was multiplied by a factor of 1.7 to obtain RON in  
order to account for some temperature rise of the MOSFETs. (RDS (ON) typically increases by a  
factor of 1.7 for a typical MOSFET as temperature increases from 25ºC to 170ºC.)  
So,  
η = POUT/PIN = 125/134.3 = 93%  
Performance Measurements of a TK2350 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 TK2350) 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 TK2350 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.  
Tripath amplifiers 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.  
32 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TC2001 Package Information  
28-pin SOIC  
33 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TP2350B Package Information  
64-pin LQFP  
Please note that the heatslug on the bottom of the package is connected to VNN.  
34 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
TP2350B Package Information  
64-pin LQFP  
35 of 36  
TK2350, Rev 1.4/04.03  
Tripath Technology, Inc. - Technical Information  
PRELIMINARY – This product is still 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.  
Contact Information  
TRIPATH TECHNOLOGY, INC  
2560 Orchard Parkway, San Jose, CA 95131  
408.750.3000 - P  
408.750.3001 - F  
For more Sales Information, please visit us @ www.tripath.com/cont_s.htm  
For more Technical Information, please visit us @ www.tripath.com/data.htm  
36 of 36  
TK2350, Rev 1.4/04.03  

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