AN520 Datasheet, PDF (5/10 Pages) Silicon Laboratories – CMOS ADVANCED GALVANIC ISOLATORS FOR MEDICAL ELECTRONICS

AN520
4.2. Defibrillator Application
Figure 3 shows the power stage for a defibrillator where two high-side/low-side isolated drivers (ISOdrivers) drive a
full-bridge circuit. Note that this circuit requires only two ISOdrivers with standard high-side bootstrap circuits to
implement a full-bridge drive solution. Each ISOdriver has an on-chip input signal conditioning circuit consisting of
Schmitt-trigger inputs, input UVLO protection, output overlap protection, and a dead time generator. These
features are essential for the reliable operation of safety-critical medical systems.
The input stage is followed by a reinforced two-channel isolator, the outputs of which connect to the gate drivers,
each isolated from the other as well as from the input. Resistors RDT1 and RDT2 determine the amount of dead
time added within each cycle. If dead time is not required, the DT inputs should be tied to the local source of VDD.
In addition to logic input ISOdrivers, Silicon Labs also offers the Si822x/6x series of enhanced, function-compatible
replacements for optically-coupled drivers. The Si822x/6x series has an input stage that mimics the behavior of an
optocoupler LED, allowing functional replacement of gate driver products, such as the HCPL-3120, yet offering
lower power operation, better performance across temperature, and higher reliability. For more information, see the
Si822x/6x series of ISOdriver data sheets available at www.silabs.com.
2.7V to 5.5V
C1
0.1 to 1.0uF
Si8234BD-C-IS
ISOdriver
VDD1
EN1
GND1
VDDA
5V to 24V
5V to 24V
HV
Q1
VIA
Control
Inputs
VIB
VOA
GNDA
5V to 24V
Si8234BD-C-IS
ISOdriver
VDD1
EN1
VDDA
GND1
2.7V to 5.5V
C1
0.1 to 1.0uF
Q3
VOA
GNDA
VIA
Control
Inputs
VIB
DT
RDT1
5V to 24V
VDDB
Q2
VOB
GNDB
T1
5V to 24V
VDDB
Q4
VOB
GNDB
DT
RDT2
Figure 3. ISOdriver-Based Defibrillator Power Stage
Rev. 0.2
5