TDA8933 Datasheet, PDF (26/47 Pages) NXP Semiconductors – Class-D audio amplifier

NXP Semiconductors
TDA8933
Class-D audio amplifier
14.2 Output current limiting
The peak output current I_OM is internally limited to 2 A (minimum). During normal
operation the output current should not exceed this threshold level, otherwise the signal is
distorted. The peak output current in SE or BTL configurations can be calculated using
Equation 5 and Equation 6.
SE configuration:
I_O(max) ≤ -_R----_L----₊-----_R---_D---⁰-_S--^.-_o⁵--_n---^×-₊---^V--_R---^P-_s---₊-----_R----_E---_S---_R- ≤ 2 A
(5)
BTL configuration:
I_O(max) ≤ -_R----_L----₊----₂-----_×-----₍-^V-_R----^PD----_S--_o---_n----₊-----_R----_s--₎ ≤ 2 A
(6)
Where:
V_P = supply voltage V_DDP1 - V_SSP1 (V) or V_DDP2 - V_SSP2 (V)
R_L = load resistance (Ω)
R_DSon = drain-source on-state resistance (Ω)
R_s = series resistance (Ω)
R_ESR = equivalent series resistance SE capacitance (Ω)
Example:
An 8 Ω speaker in the BTL configuration can be used up to a supply voltage of 18 V
without running into current limiting. Current limiting (clipping) will avoid audio holes but
produces a similar distortion to voltage clipping.
14.3 Speaker configuration and impedance
For a flat frequency response (second order Butterworth filter) it is necessary to change
the low-pass filter components L_LC and C_LC according to the speaker configuration and
impedance. Table 14 shows the required values in practice.
Table 14. Filter component values
Configuration
SE
R_L (Ω)
4
6
8
BTL
8
16
L_LC (µH)
22
33
47
22
47
C_LC (nF)
680
470
330
680
330
TDA8933_1
Preliminary data sheet
Rev. 01 — 15 May 2007
© NXP B.V. 2007. All rights reserved.
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