MLX90719 查看數據表（PDF） - Melexis Microelectronic Systems

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MLX90719

General purpose timer

Melexis Microelectronic Systems  

MLX90719

General purpose timer

If OXBAT = 1 the clock interrupts are generated at the rate of 128Hz (Crystal frequency divided by 256).

If OXBAT = 0 the clock interrupts are generated at the rate of twice the mains frequency by the zero crossing

detector (combination of signals ZOUT1 and ZOUT2) that is 100Hz or 120Hz.

The main purpose of the timer interrupt is to rate the multiplexing of the LCD but it can be used to control a

triac.

Each interrupt can be enabled/disabled and cleared by setting or resetting ESUPI, ECLKI and ETIMI in P7.

As several interrupts may occur at the same time a fourth control bit RFHIT (of P7) has been implemented to

refresh the interrupt controller after each interrupt subroutine. The flow chart shows the interrupt process:

Debouncing

A debounce circuit eliminates negative spikes on line APORL to avoid unexpected supply interrupts due to dis-

turbances. The debounce time (tdaporl) depends on OXBAT.

If OXBAT = 1 it derives from the crystal oscillator frequency and:

7.8ms < tdaporl < 11.7ms

If OXBAT = 0 it derives from the low power RC oscillator frequency and:

3.2ms < tdaporl < 24ms

Both outputs of the zero crossing detector are combined in a debounce circuit that generates a periodic signal

rising at each zero crossing of the mains without delay. This signal (ZCD) is connected to the interrupt handler

(if OXBAT = 0) at bit PCLKI. The debounce period is typically 2ms but can vary from 0.6ms to 6ms because is it

generated from the low power RC oscillator.

Zero crossing signal on P7

The zero crossing signal is readable at bit ZCD of P7. This feature may be used to detect zero crossing in crys-

tal-based applications.

PWM generator

The three relay drivers of the MLX90719 can be driven independently at 0%, 14.3%, 28.6% and 100% duty cy-

cle (except driver A which can not be driven at 100% duty).

Bits PA0 to PC1 of P5 set the duty cycle of each driver (signals POUTA, POUTB and POUTC) and bit INTCUR

activates the current peak generator (signal PINT):

INTCUR

Px1

Px0

Duty cycle of Duty cycle of

POUTx

PINT

X

0

0

0%

X

0

1

14.3 %

X

1

0

100 % *

X

1

1

28.6 % for t30 then

14.3%

0

X

X

0%

1

X

X

14.3%

Note: * = 0% for driver A

t30 is given by: tclki < t30 < 2tclki

where tclki is the delay between two clock interrupts:

tclki = 10ms if zero crossing detector is used and Fmains = 50Hz

tclki = 8.33ms if zero crossing detector is used and Fmains = 60Hz

tclki = 7.81ms if crystal oscillator is used

In all cases: 7.81ms < t30 < 15ms

The PWM frequency is programmable. It depends on the main oscillator frequency and on the 6-bit divide ratio

written in P6:

MMLLXX990027xx19NaGmeeneofraSl epnusroprose timer

RePvaYg.Xe 15

22/Aug/98 Rev 1.0 3P0a/gJeul1/050

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