SI88X2X Datasheet, PDF (22/45 Pages) Silicon Laboratories – Isolation of up to 5000 Vrms

Si88x2x
2.3.10. Low-Voltage Configuration
The low-voltage configuration is used for converting 3.0 V to 5.5 V. All product options of the Si882xx and Si883xx
are intended for this configuration.
An advantage of Si88xx devices over other converters that use this same topology is that the output voltage is
sensed on the secondary side without requiring additional optocouplers and support circuitry to bias those
optocouplers. This allows the dc-dc to operate with superior line and load regulation while reducing external
components and increasing lifetime reliability.
In a typical digital signal isolation application, the dc-dc powers the Si882xx and Si883xx VDDB as shown in
Figure 8. In addition to powering the isolated side of the dc-dc can deliver up to 2 W of power to other loads. The
dc-dc requires an input capacitor, C2, blocking capacitor, C1, transformer, T1, rectifying diode, D1, and an output
capacitor, C3. Resistors R1 and R2 divide the output voltage to match the internal reference of the error amplifier.
Type 1 loop compensation made by RCOMP and CCOMP are required at the COMP pin. Though it is not
necessary for normal operation, we recommend that a snubber be used to minimize radiated emissions. More
details can be found in “AN892: Design Guide for Isolated DC-DC Using the Si882xx/883xx”.
Vin
C₁
T₁
D₁
C₂
C₃
Vout
R1
Si8832x
R2
VDDA
UVLO
VSW
RFSW SH_FC
SS
CSS
Power
FET
Power
FET
DC-DC
Controller
Freq. Control
and Shutdown
Soft Start
A1
Rev. Digital
Channels
A2
HF RX
HF TX
HF TX
UVLO
HVREG
Reference
Error Amp
and
Compensation
HF TX
HF RX
Encoder
HF RX
VDDB
VREG
Used in applications
where converter
output is > 5.5 V
VSNS
COMP
CCOMP
RCOMP
B1
Fwd. Digital
Channels
B2
Figure 8. Si88xx Block Diagram: 3 V–5 V Input to 3 V–5 V Output
22
Rev. 0.5