TDA8933B Datasheet, PDF (24/42 Pages) NXP Semiconductors – Class D audio amplifier

NXP Semiconductors
TDA8933B
Class D audio amplifier
14.2 Output current limitation
The peak output current I_O(max) is internally limited to a minimum value of 2 A. During
normal operation the output current should not exceed this threshold level, otherwise the
signal will be 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 output inductor (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 with an output frequency of
40 kHz) 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 values required 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
TDA8933B_1
Preliminary data sheet
Rev. 01 — 23 October 2008
© NXP B.V. 2008. All rights reserved.
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