C =

i

1

2

Z f

p

i

c

f

=

c

1

2

Z C

p

i

i

-3dB

f=

1

2

Z C

p

i

i

IN

Input

Signal

TPA3110D2-Q1

www.ti.com

SLOS794B – SEPTEMBER 2012 – REVISED SEPTEMBER 2015

Typical Application (continued)

8.2.2.5 Input Resistance

Changing the gain setting can vary the input resistance of the amplifier from its smallest value, 9 k

Ω ±20%, to the

largest value, 60 k

Ω ±20%. As a result, if a single capacitor is used in the input high-pass filter, the –3 dB or

cutoff frequency may change when changing gain steps.

(2)

pass filter with the corner frequency determined in Equation 3.

(3)

reconfigured as Equation 4.

(4)

leakage current creates a DC offset voltage at the input to the amplifier that reduces useful headroom, especially

in high gain applications. For this reason, a low-leakage tantalum or ceramic capacitor is the best choice. When

polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most

applications as the DC level there is held at 3 V, which is likely higher than the source DC level. Note that it is

important to confirm the capacitor polarity in the application. Additionally, lead-free solder can create DC offset

voltages and it is important to ensure that boards are cleaned properly.

8.2.2.7 BSN and BSP Capacitors

The full H-bridge output stages use only NMOS transistors. Therefore, they require bootstrap capacitors for the

high side of each output to turn on correctly. A 0.22-

μF ceramic capacitor, rated for at least 25 V, must be

connected from each output to its corresponding bootstrap input. Specifically, one 0.22-

μF capacitor must be

connected from OUTPx to BSPx, and one 0.22-

μF capacitor must be connected from OUTNx to BSNx. (See the

application circuit diagram in TPA3110D2-Q1 Simplified Application Schematic .)

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