ST52T400 datasheet(64/94 Pages) STMICROELECTRONICS

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ST52T400/T440/E440/T441

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Burst Mode

The Burst principle is based on turning the TRIAC

device on and off for a fixed integer number of

mains voltage periods, in order to control the

power transferred to the load.

In Burst Mode the peripheral provides a signal,

with a fixed period T containing an integer number

of pulses corresponding to the main voltage zero

crossings, with a Duty Cycle that is proportional to

the number of pulses that keep the TRIAC on (Fig-

ure 10.4).

The user can define the period T by means of the

internal 16-bit prescaler, setting REG_CONF8 and

REG_CONF9 (Figure 10.2). T is proportional to

the main voltage period and is in the range [5.10,

334233.6]s if the main frequency is 50Hz.

The duty cycle is fixed at each period by an 8-bit

value loaded in the TRIAC_COUNT register (Out-

put Register 9). The duty cycle is proportional to

the value: loading 50% duty cycle is obtained,

loading 0 the output will be low (off) during all the

period, loading 255 will be high (on).

The width and the polarity of the pulses can be

programmed according to the TRIAC device and

the circuit characteristics.

In order to work in Burst mode, the pre-post zero-

crossing of main voltage must be detected by

using an external inserting circuitry connected to

the MAIN1 and MAIN2 pins (Figure 10.5).

This kind of TRIAC control is mainly used for ther-

mal regulation.

PhaseAnglePartialization Mode

Phase Angle Partialization method is based on

turning on the TRIAC device only for a part (Phase

Angle) of each main voltage period. When the

phase angle is large, the energy (power) supplied

to the load is low, viceversa when the phase angle

is small, the energy supplied to the load is high.

In order to work in Phase Angle Partialization

mode, the zero-crossing of main voltage must be

detected by using an external inserting circuitry

connected to the MAIN1 and MAIN2 pins or,

optionally, only on MAIN1 pin (Figure 10.10).

In this working mode, the peripheral provides eight

pulses after the time corresponding to the Phase

Angle on the TROUT pin, obtained by setting the

TRIAC_COUNT 8-bit register (Output Register 9)

and

the

Prescaler

(REG_CONF8

and

REG_CONF9). By modifying the TRIAC_COUNT

10.1 TRIAC/PWM Driver Setting

The TRIAC/PWM Peripheral can be SET or

RESET through REG_CONF10(7) bit TCRST

(Table 10.3) in all three working modes.

If the TRIAC/PWM Peripheral is SET and only in

PWM mode, it is possible to START or STOP the

internal counter of the peripheral without resetting

it, through REG_CONF10(5) bit TCST (Table

10.3), in order to use the peripheral as an addi-

tional Timer. In the other modes the TCST bit

must be kept to “1”.

NOTE:

if TCRST is 0 (reset status) the TROUT

pin output is in tristate.

Figure 10.2 TRIAC/PWM Configuration Registers 8 and 9

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