SI8751 Datasheet, PDF (7/27 Pages) Silicon Laboratories – Digital CMOS input option

3. Applications
The following examples illustrate typical circuit configurations using the Si8751/52.
3.1 DC SSR Example
The Si875x device can be used to control a dc load as shown in the following figure:
VDD
TT
MCAP1
Si8751/52 Data Sheet
Applications
VDC
IN
GND
GATE
SOURCE
MCAP2 (NC)
DC Load
Figure 3.1. Driving an FET for DC Load Including Miller Clamp Capacitor
In this configuration, the Si8751 charges the gate of the external FET; turning it on. This switches on power, supplied by VDC, to the
load. The output side circuitry is identical if using the Si8752.
3.2 AC SSR Example
The Si875x can be used to control power to an ac load using the following circuit:
VDD
TT
IN
GND
MCAP1
AC Load
GATE
SOURCE
MCAP2
AC
Supply
Figure 3.2. Driving FETs for AC Load Switching
In this configuration, both FET’s are turned on by the charge delivered by the Si8751. This allows ac current to flow to the load. When
the Si875x is turned off, charge is drained form the gates of both FET’s and the ac current is turned off. The output side circuitry is
identical if using the Si8752.
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