JAJSKP7 December 2020 TAS5822M
PRODUCTION DATA
It is required that the peak current is smaller than the OCP (Over current protection) value which is 7A (Typical) , there are 3 cases which cause high peak current flow through inductor.
θ = 0.5 (BD Modulation), 0.14 (1SPW Modulation), 0.14 (Hybrid Modulation)
Table 8-2 shows the start-up current related to different Fsw, PVDD, Inductance and different PWM modulation scheme. Start-up current should within device's OCETHRES.
Modulation Scheme | PVDD (V) | FSW ((kHz)) | LC filter | Startup Peak Current (A) |
---|---|---|---|---|
BD | 13.5 | 384 | 4.7 µH + 0.68 µF | 2.88 |
10 µH + 0.68 µF | 2 | |||
768 | 4.7 µH + 0.68 µF | 2.64 | ||
10 µH + 0.68 µF | 1.84 | |||
18 | 384 | 4.7 µH + 0.68 µF | 3.84 | |
10 µH + 0.68 µF | 2.64 | |||
768 | 4.7 µH + 0.68 µF | 3.52 | ||
10 µH + 0.68 µF | 2.4 | |||
24 | 384 | 4.7 µH + 0.68 µF | 5.4 | |
10 µH + 0.68 µF | 3.76 | |||
768 | 4.7 µH + 0.68 µF | 5 | ||
10 µH + 0.68 µF | 3.12 | |||
1SPW | 13.5 | 384 | 4.7 µH + 0.68 µF | 1.28 |
10 µH + 0.68 µF | 0.96 | |||
768 | 4.7 µH + 0.68 µF | 1.12 | ||
10 µH + 0.68 µF | 0.72 | |||
18 | 384 | 4.7 µH + 0.68 µF | 1.84 | |
10 µH + 0.68 µF | 1.2 | |||
768 | 4.7 µH + 0.68 µF | 1.52 | ||
10 µH + 0.68 µF | 1.04 | |||
24 | 384 | 4.7 µH + 0.68 µF | 2.6 | |
10 µH + 0.68 µF | 1.6 | |||
768 | 4.7 µH + 0.68 µF | 2.4 | ||
10 µH + 0.68 µF | 1.36 |
Figure 8-3 and Figure 8-4 shows how modulation scheme affect the start-up current. OUTP_PWM is Class D amplifier's PWM output, OUTP_FILTER is the common mode voltage on the capacitor of LC filter.
Same PVDD and switching frequency, larger inductance means smaller idle current for lower power dissipation. It's suggested that inductor's saturation current Isat, is larger than the amplifier's peak current during power-up and playing audio. In addition, the effective inductance at the peak current is required to be at least 80% of the inductance value in Table 8-3 to meet datasheet specifications.
Switching Frequency (kHz) | Modulation Scheme | Recommended Minimum Inductance (uH) for LC filter design |
---|---|---|
1024 | 1SPW | 3.3 µH (or larger) + Capacitor (0.22uF~0.68uF) |
768 | 4.7 µH (or larger) + Capacitor (0.22uF~0.68uF) | |
384 or 480 | 10 µH (or larger) +Capacitor (0.22uF~0.68uF) | |
384~1024 | BD | 8.2uH (or Larger) +Capacitor (0.22uF~0.68uF) |