TPA3008D2_07 Datasheet, PDF (18/29 Pages) Texas Instruments – 10-W STEREO CLASS-D AUDIO POWER AMPLIFIER

TPA3008D2
SLOS435A – MAY 2004 – REVISED JULY 2004
www.ti.com
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 220-nF ceramic capacitor, rated for at least 25 V, must be
connected from each output to its corresponding bootstrap input. Specifically, one 220-nF capacitor must be
connected from xOUTP to xBSP, and one 220-nF capacitor must be connected from xOUTN to xBSN. (See the
application circuit diagram in Figure 16.)
The bootstrap capacitors connected between the BSxx pins and corresponding output function as a floating
power supply for the high-side N-channel power MOSFET gate drive circuitry. During each high-side switching
cycle, the bootstrap capacitors hold the gate-to-source voltage high enough to keep the high-side MOSFETs
turned on.
VCLAMP Capacitors
To ensure that the maximum gate-to-source voltage for the NMOS output transistors is not exceeded, two
internal regulators clamp the gate voltage. Two 1-µF capacitors must be connected from VCLAMPL (pin 25) and
VCLAMPR (pin 36) to ground and must be rated for at least 25 V. The voltages at the VCLAMP terminals vary
with V_CC and may not be used for powering any other circuitry.
Internal Regulated 5-V Supply (AV_DD)
The AV_DD terminal (pin 29) is the output of an internally generated 5-V supply, used for the oscillator,
preamplifier, and volume control circuitry. It requires a 1-µF capacitor, placed close to the pin, to keep the
regulator stable.
This regulated voltage can be used to control GAIN0 and GAIN1 terminals, but should not be used to drive
external circuitry.
Differential Input
The differential input stage of the amplifier cancels any noise that appears on both input lines of the channel. To
use the TPA3008D2 with a differential source, connect the positive lead of the audio source to the INP input and
the negative lead from the audio source to the INN input. To use the TPA3008D2 with a single-ended source, ac
ground the INP or INN input through a capacitor equal in value to the input capacitor on INN or INP and apply
the audio source to either input. In a single-ended input application, the unused input should be ac grounded at
the audio source instead of at the device input for best noise performance.
SHUTDOWN OPERATION
The TPA3008D2 employs a shutdown mode of operation designed to reduce supply current (I_CC) to the absolute
minimum level during periods of nonuse for power conservation. The SHUTDOWN input terminal should be held
high (see specification table for trip point) during normal operation when the amplifier is in use. Pulling
SHUTDOWN low causes the outputs to mute and the amplifier to enter a low-current state. Never leave
SHUTDOWN unconnected, because amplifier operation would be unpredictable.
For the best power-off pop performance, place the amplifier in the shutdown mode prior to removing the power
supply voltage.
USING LOW-ESR CAPACITORS
Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal) capacitor
can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this resistor
minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this resistance,
the more the real capacitor behaves like an ideal capacitor.
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