TPA2011D1 Datasheet, PDF (11/23 Pages) Texas Instruments – 3.2W Mono Filter-Free Class-D Audio Power Amplifier With Auto-Recovering Short-Circuit Protection

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TPA2011D1
SLOS626 – DECEMBER 2009
APPLICATION INFORMATION
SHORT CIRCUIT AUTO-RECOVERY
When a short-circuit event occurs, the TPA2011D1 goes to shutdown mode and activates the integrated
auto-recovery process whose aim is to return the device to normal operation once the short-circuit is removed.
This process repeatedly examines (once every 100ms) whether the short-circuit condition persists, and returns
the device to normal operation immediately after the short-circuit condition is removed. This feature helps protect
the device from large currents and maintain a good long-term reliability.
INTEGRATED IMAGE REJECT FILTER FOR DAC NOISE REJECTION
In applications which use a DAC to drive Class-D amplifiers, out-of-band noise energy present at the DAC's
image frequencies fold back into the audio-band at the output of the Class-D amplifier. An external low-pass filter
is often placed between the DAC and the Class-D amplifier in order to attenuate this noise.
The TPA2011D1 has an integrated Image Reject Filter with a low-pass cutoff frequency of 130 kHz, which
significantly attenuates this noise. Depending on the system noise specification, the integrated Image Reject
Filter may help eliminate external filtering, thereby saving board space and component cost.
COMPONENT SELECTION
Figure 28 shows the TPA2011D1 typical schematic with differential inputs and Figure 29 shows the TPA2011D1
with differential inputs and input capacitors, and Figure 30 shows the TPA2011D1 with single-ended inputs.
Differential inputs should be used whenever possible because the single-ended inputs are much more
susceptible to noise.
Table 1. Typical Component Values
REF DES
R_I
C_S
C_I ⁽¹⁾
VALUE
150 kΩ (±0.5%)
1 μF (+22%, –80%)
3.3 nF (±10%)
EIA SIZE
0402
0402
0201
MANUFACTURER
Panasonic
Murata
Murata
PART NUMBER
ERJ2RHD154V
GRP155F50J105Z
GRP033B10J332K
(1) C_I is only needed for single-ended input or if V_ICM is not between 0.5 V and V_DD – 0.8 V. C_I = 3.3 nF
(with R_I = 150 kΩ) gives a high-pass corner frequency of 321 Hz.
Input Resistors (R_I)
The input resistors (R_I) set the gain of the amplifier according to Equation 1.
ǒ Ǔ Gain
+
2
x
150
RI
kW
V
V
(1)
Resistor matching is very important in fully differential amplifiers. The balance of the output on the reference
voltage depends on matched ratios of the resistors. CMRR, PSRR, and cancellation of the second harmonic
distortion diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors or
better to keep the performance optimized. Matching is more important than overall tolerance. Resistor arrays with
1% matching can be used with a tolerance greater than 1%.
Place the input resistors very close to the TPA2011D1 to limit noise injection on the high-impedance nodes.
For optimal performance the gain should be set to 2 V/V or lower. Lower gain allows the TPA2011D1 to operate
at its best, and keeps a high voltage at the input making the inputs less susceptible to noise.
Decoupling Capacitors (C_S1, C_S2)
The TPA2011D1 is a high-performance class-D audio amplifier that requires adequate power supply decoupling
to ensure the efficiency is high and total harmonic distortion (THD) is low. For higher frequency transients,
spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor C_S1 = 0.1μF ,
placed as close as possible to the device V_DD lead works best. Placing C_S1 close to the TPA2011D1 is important
for the efficiency of the class-D amplifier, because any resistance or inductance in the trace between the device
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s) :TPA2011D1
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