TDA8922C Datasheet, PDF (18/40 Pages) NXP Semiconductors – 2 X 75 W class-D power amplifier

NXP Semiconductors
TDA8922C
2 × 75 W class-D power amplifier
13.3.2 Bridge-Tied Load (BTL)
Maximum output power:
P_o(0.5%) = ----^R--------^L---------^{+----------R--------D------S------o}------ⁿ------⁽--^R--^h----^s--^L----⁾------⁺----------^R--------^D-------^S-----o------ⁿ------⁽----^l---^s-----)---^×-----⁽--^V----₂-^D---_R^D----_L-^–-----^V----^S---^S---⁾----^×----⁽---¹----^–----^t--^w----⁽--^m----ⁱ--ⁿ--⁾---^×-----⁰---^.--⁵----^f---^o---^s--^c--⁾-----²-
(3)
Maximum output current internally limited to 6 A:
I_{o( peak)} = -_R⁽--^V--_L---^D-₊--^D---₍--_R^–----_D-^V---_S-^S--_o-^S-_n--⁾-₍--_h-^×--_s--₎⁽---¹₊----^–-_R----^t_D--^w--_S-⁽--_om---_n-ⁱ-₍-ⁿ-_l--⁾_s--₎-^×-₎----⁰₊---^.-⁵-₂---_Rf---^o-_s--^s₍--^cL---⁾₎
(4)
Where:
• P_{o(0.5 %)}: output power at the onset of clipping
• R_L: load impedance
• R_DSon(hs): high-side R_DSon of power stage output DMOS (temperature dependent)
• R_DSon(ls): low-side R_DSon of power stage output DMOS (temperature dependent)
• R_s(L): series impedance of the filter coil
• V_P: single-sided supply voltage or 0.5 × (V_DD + |V_SS|)
• t_w(min): minimum pulse width (typical 100 ns, temperature dependent)
• f_osc: oscillator frequency
Remark: Note that I_o(peak) should be less than 6 A; see Section 8.3.2. I_o(peak) is the sum of
the current through the load and the ripple current. The value of the ripple current is
dependent on the coil inductance and the voltage drop across the coil.
13.4 External clock
To ensure duty cycle-independent operation, the external clock frequency is divided by
two internally. The external clock frequency is therefore twice the internal clock frequency
(typically 2 × 350 kHz = 700 kHz).
If several Class D amplifiers are used in a single application, it is recommended that all
the devices run at the same switching frequency. This can be achieved by connecting the
OSC pins together and feeding them from an external oscillator. When using an external
oscillator, it is necessary to force pin OSC to a DC level above SGND. This disables the
internal oscillator and causes the PWM to switch at half the external clock frequency.
The internal oscillator requires an external resistor R_OSC, connected between pin OSC
and pin VSSA. R_OSC must be removed when using an external oscillator.
The noise generated by the internal oscillator is supply voltage dependent. An external
low-noise oscillator is recommended for low-noise applications running at high supply
voltages.
13.5 Heatsink requirements
An external heatsink must be connected to the TDA8922C.
TDA8922C_1
Product data sheet
Rev. 01 — 7 September 2009
© NXP B.V. 2009. All rights reserved.
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