AN2716 datasheet(6/28 Pages) STMICROELECTRONICS

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STCC08 description

AN2716

6/28

Doc ID 14460 Rev 2

1.3

AC switch control

The STCC08 controls up to 10 mA IGTTRIAC, ACST and ACS through the “gate driver”

block designed to:

●

Drive the AC switch according to the IN control input state (CMOS compatible)

–

For IN = 1 = VCC

the AC switch is turned on

–

For IN = 0 = GND

the AC switch is turned off

●

Regulate the gate current of the AC switch thanks to the internal current controller

The gate current value (Pin G - to turn on the AC switch) is defined by the external resistor

RIG value (resistor connected between the STCC08 RIG input and ground). Figure 4 gives

the maximum value of this resistor (RIG_max) according to the minimum ambient

temperature (Tamb_min) of the appliance for two AC switch IGT values. Note that as the AC

switch junction temperature increases when the AC switch is on (Tj > Tamb), the IG gate

current required to turn on the AC switch decreases (IG < IGT). So only the minimum

ambient temperature has to be considered.

Figure 4.

Resistor RIG value according to the minimum ambient temperature and

AC switch IGT

For example, with a 10 mA IGT AC switch and a -20 °C minimum ambient temperature, a

maximum 30

Ω RIG resistor can be used to turn on the AC switch throughout the whole

appliance temperature range.

1.4

AC switch failure mode detection

1.4.1

STCC08 AVF output configuration

The STCC08 AVF driver block is used to send the AC switch state to the MCU (see

Section 1.4.2). The STCC08 AVF output is an open collector and can be loaded with an

external resistor (RAVF) or connected directly to the MCU, in pull-up input configuration (see

Figure 5).

100

110

120

130

-20

-15

-10

-5

1015202530

Tamb_min (°C)

IGT 10mA @ 25 °C

IGT 5mA @ 25 °C

RIG_max ()

IGT AC Switch:

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