SI823X Datasheet, PDF (30/52 Pages) Silicon Laboratories – 0.5 AND 4.0 AMP ISODRIVERS (2.5 AND 5 KVRMS)

Si823x
7.2. Dual Driver
Figure 44 shows the Si823x configured as a dual driver. Note that the drain voltages of Q1 and Q2 can be
referenced to a common ground or to different grounds with as much as 1500 V dc between them.
VDDI
C1
10 µF
VDDI
GNDI
Q1
VOA
VDDA
PH1
PH2
VIA
VDDA
C2
VIB
10 µF
GNDA
CONTROLLER
Si8235/6
VDDB
VDDB
C3
I/O
DISABLE
10 µF
GNDB
Q2
VOB
Figure 44. Si8235 in a Dual Driver Application
7.3. Dual Driver with Thermally Enhanced Package (Si8236)
The thermal pad of the Si8236 must be connected to a heat spreader to lower thermal resistance. Generally, the
larger the thermal shield’s area, the lower the thermal resistance. It is recommended that a thermal vias also be
used to add mass to the shield. Vias generally have much more mass than the shield alone and consume less
space, thus reducing thermal resistance more effectively. While the heat spreader is not generally a circuit ground,
it is a good reference plane for the Si8236 and is also useful as a shield layer for EMI reduction.
With a 10mm² thermal plane on the outer layers (including 20 thermal vias), the thermal impedance of the Si8236
was measured at 50 °C/W. This is a significant improvement over the Si835 which does not include a thermal pad.
The Si8235’s thermal resistance was measured at 105 °C /W.
30
Rev. 0.3