Datasheet

C
I2
u
1
ǒ
2p 150kW 20Hz
Ǔ
(9)
C
I2
u 53pF
(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
Summing Two Single-Ended Input Signals
TPA2005D1
SLOS369F – JULY 2002 – REVISED JULY 2008 ............................................................................................................................................................... www.ti.com
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. Phone gain is set at gain 1 = 0.1 V/V, and the ring-tone gain is set
to gain 2 = 2 V/V, the resistor values would be …
• R
I1
= 3 M Ω , and = R
I2
= 150 k Ω .
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 36. Application Schematic With TPA2005D1 Summing Differential Input and
Single-Ended Input Signals
Four resistors and three capacitors are needed for summing single-ended input signals. The gain and corner
frequencies (f
c1
and f
c2
) for each input source can be set independently (see equations Equation 11 through
Equation 14 , and Figure 37 ). Resistor, R
P
, and capacitor, C
P
, are needed on the IN+ terminal to match the
impedance on the IN- terminal. The single-ended inputs must be driven by low impedance sources even if one of
the inputs is not outputting an ac signal.
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Product Folder Link(s): TPA2005D1