Datasheet

Summing a Differential Input Signal and a Single-Ended Input Signal
Gain 1 +
V
O
V
I1
+
2 x 150 kW
R
I1
ǒ
V
V
Ǔ
(6)
Gain 2 +
V
O
V
I2
+
2 x 150 kW
R
I2
ǒ
V
V
Ǔ
(7)
C
I2
+
1
ǒ
2p R
I2
f
c2
Ǔ
(8)
C
I2
u
1
ǒ
2p 150kW 20Hz
Ǔ
(9)
C >53nF
I2
(10)
_
+
IN-
IN+
PWM H-
Bridge
V
O+
V
O-
Internal
Oscillator
C
S
To Battery
V
DD
GND
Bias
Circuitry
R
I2
R
I2
Differential
Input 1
Filter-Free Class D
SHUTDOWN
R
I1
R
I1
Single-Ended
Input 2
C
I2
C
I2
TPA2006D1
www.ti.com ................................................................................................................................................. SLOS498A – SEPTEMBER 2006 – REVISED JULY 2008
Figure 31 shows how to sum a differential input signal and a single-ended input signal. Ground noise can couple
in through IN+ with this method. It is better to use differential inputs. The corner frequency of the single-ended
input is set by C
I2
, shown in Equation 8 . To assure that each input is balanced, the single-ended input must be
driven by a low-impedance source even if the input is not in use
If summing a ring tone and a phone signal, the phone signal should use a differential input signal while the ring
tone might be limited to a single-ended signal.
The high pass corner frequency of the single-ended input is set by C
I2
. If the desired corner frequency is less
than 20 Hz:
Figure 31. Application Schematic With TPA2006D1 Summing Differential Input and Single-Ended Input
Signals
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