TDA8946AJ Datasheet, PDF (5/20 Pages) NXP Semiconductors – 2 x 15 W BTL audio amplifier with DC gain control

Philips Semiconductors
TDA8946AJ
2 x 15 W BTL audio amplifier with DC gain control
The input cut-off frequency is:
f _{i(cut – off )} = ₂----_π----₍--₀---_.-₅-----_×-¹----_R----_i---_×----_C-----_i--₎
(1)
For R_i = 32 kΩ and C_i = 220 nF:
f _{i(cut – off )} = -₂---_π----₍--₀---_.-₅-----_×-----₃---₂----_×-----₁---¹⁰---₃----_×-----₂---₂---₀-----_×----₁---₀----_–--₉---₎ = 45.2 Hz
(2)
As shown in Equation 2, large capacitors values for the inputs are not necessary; so
the switch-on delay during charging of the input capacitors can be minimized. This
results in a good low frequency response and good switch-on behaviour.
Remark: To prevent high frequency oscillations do not leave the inputs open, connect
a capacitor of 4.7 nF across the input pins close to the device (see Figure 15).
8.2 Power amplifier
The power amplifier is a Bridge-Tied Load (BTL) amplifier with an all-NPN output
stage, capable of delivering a peak output current of 2 A.
The BTL principle offers the following advantages:
• Lower peak value of the supply current
• The ripple frequency on the supply voltage is twice the signal frequency
• No expensive DC-blocking capacitor
• Good low frequency performance.
8.2.1 Output power measurement
The output power as a function of the supply voltage is measured on the output pins
at THD = 10%; see Figure 10. The maximum output power is limited by the supply
voltage of 18 V and the maximum available output current: 2 A repetitive peak
current.
8.2.2 Headroom
Typical CD music requires at least 12 dB (factor 15.85) dynamic headroom -
compared to the average power output - for transferring the loudest parts without
distortion. At V_CC = 18 V, R_L = 8 Ω and P_o = 10 W at THD = 0.5% (see Figure 8), the
Average Listening Level (ALL) - music power - without any distortion yields:
P_o(ALL) = ₁-¹--₅-⁰--_.--₈-^W--₅-- = 631 mW
(3)
The power dissipation can be derived from Figure 12 on page 11 for 0 dB
respectively 12 dB headroom.
9397 750 09434
Product data
Rev. 01 — 01 March 2002
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
5 of 20