AN2859 Datasheet, PDF (1/29 Pages) STMicroelectronics – Multiplexed diagnostics of AC switches using two STCC08

AN2859
Application note
Multiplexed diagnostics of AC switches
using two STCC08
Introduction
The aim of this application note is to present opportunities to reduce the number of input
pins used on a microcontroller unit (MCU) to diagnose failures of several AC switches with
the STCC08. This document deals with the multiplexed diagnostics of two STCC08 and
gives technical recommendations on the implementation of this solution.
STCC08 overview
The STCC08 has been designed to improve home appliance safety. This new device can
drive an AC switch (Triac, ACST and ACS) with a gate current I_GT up to 10 mA and to send
back to the microcontroller unit a signal image of the voltage across the controlled AC
switch (this signal defines the AC switch state). The STCC08 has three functional blocks
(see Figure 1).
• A "gate driver" block used to drive an AC switch and to interface directly the STCC08 with
the MCU (CMOS compatible)
• A "power switch signal shaping" block used to measure the AC switch voltage in both AC
line cycles
• An "AVF driver" block used to give an image of the AC switch voltage to the MCU (digital
information)
Figure 1. STCC08 block diagram
G
Gate driver
IN
+
-
RIG
IN
STCC08
AVF
VCC
N/C
AVF driver
AVF
AC
AC
Power switch
signal shaping
GND
1
8
2
7
3
6
4
5
SO -8
GND
RIG
G
VCC
For more information about the STCC08, please refer to the ST Application note AN2716.
July 2014
DocID15255 Rev 2
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www.st.com
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