SI824X Datasheet, PDF (23/30 Pages) Silicon Laboratories – CLASS D AUDIO DRIVER WITH PRECISION DEAD-TIME GENERATOR

Si824x
4. Applications
The following examples illustrate typical circuit configurations using the Si824x.
4.1. Class D Digital Audio Driver
Figures 39 and 40 show the Si8241/4 controlled by a single PWM signal. Supply can be unipolar (0 to 1500 V) or
bipolar (± 750 V).
PWMOUT
CONTROLLER
I/O
VDDI
VDDI
C1
1uF
GNDI
PWM
VDD2 ^D1
C2
1 µF
VDDA
1500 V max
VOA
CB
Q1
DT
GNDA
RDT
Si8241/4
VDDB
VDDB
DISABLE
GNDB
C3
10uF
Q2
VOB
Figure 39. Si824x in Half-Bridge Audio Application
PWMOUT
VDDI
VDDI
C1
1uF
GNDI
PWM
VDD2 ^D1
C2
1 µF
VDDA
+750 V max
VOA
CB
Q1
CONTROLLER
I/O
DT
GNDA
RDT
Si8241/4
VDDB
VDDB
DISABLE
GNDB
C3
10uF
Q2
VOB
-750 V max
Figure 40. Si824x in Half-Bridge Audio Application
D1 and CB form a conventional bootstrap circuit that allows VOA to operate as a high-side driver for Q1, which has
a maximum drain voltage of 1500 V. VOB is connected as a conventional low-side driver. Note that the input side of
the Si824x requires VDD in the range of 4.5 to 5.5 V, while the VDDA and VDDB output side supplies must be
between 6.5 and 24 V with respect to their respective grounds. The boot-strap start up time will depend on the CB
cap chosen. VDD2 is usually the same as VDDB. Also note that the bypass capacitors on the Si824x should be
located as close to the chip as possible. Moreover, it is recommended that 0.1 and 10 µF bypass capacitors be
used to reduce high frequency noise and maximize performance. The D1 diode should be a fast-recovery diode; it
should be able to withstand the maximum high voltage (e.g. 1500 V) and be low-loss. See “AN486: High-Side
Bootstrap Design Using Si823x ISODrivers in Power Delivery Systems” for more details in selecting the bootstrap
cap (CB) and diode (D1).
Rev. 1.0
23