MLX90805
Intelligent Triac Controller
Features and Benefits
“Soft Start” Eliminates Current Surges
Integrated Design Eliminates External Components
Drives Virtually Any Resistive or Inductive Load
Built–in Thermal Protection
Digital Design For Stable Triac Control
Immune to Lifetime and Thermal Drift
Low Power Consumption
50Hz/60Hz Operation
Applications
AC Light Dimmer
Soft-Start AC Motor Controller
Variable-Speed AC Motor Controller
Ordering Information
Part No.
Temperature Suffix
Package
version
Temperature Range
MLX90805
S
A
-x
0C to 85C
MLX90805
S
L
-x
0C to 85C
The customer specific version code (defining the options) is indicated with 1 character at
the end of the ordering number.
Functional Diagram
Description
The MLX90805 is a power control IC ideally suited
for
control of any resistive or inductive load
regulated by a triac.
The chip was designed primarily for starting and
speed control of AC motors, but will work equally well
with any Inductive or resistive load such as
Incandescent lights.
The chip’s primary purpose is to provide a “soft start”
for a motor, preventing current inrush. The triac is
controlled by a linear “ramp” from minimum to
maximum power. Start rate can be varied from 0.5
sec. to 3 sec, by changing the option bits.
The secondary function of the 90805 is proper
ignition of the triac for inductive and resistive loads,
while keeping the triac’s current consumption to a
minimum.
Added features include a frequency locked loop for
stable ignition point.
Vss
90805
Voltage
regulator
Vdda
Power monitoring
and reset
ZCD
zero
crossing
detector
Triac driver
Auto
retriggering
SET
ADC
Lookup
ROM
Vref/2
COMP
Logic
Vref
Options
Vref
THP
FB
MLX902xx Name of Sensor
Controller
MLX90805 Intelligent Triac
Rev Y.X
1
Page
22/Aug/98
Page 1
Rev 1.2 17/May/00
MLX90805
Intelligent Triac Controller
Description of Block Diagram
Voltage Regulator
The chip is supplied from the AC line voltage, by a
half wave rectifier. The voltage at pin VDDA is limited
to ~ 15.5V. The digital part and some of the periph-
eral blocks are supplied by internally generated VDD
~ 5V.
Logic
This block performs all control functions to realize
time synchronization, smooth soft start, and proper
triac firing, so that motor runs at a defined speed.
Triac Driver
This output is able to drive directly a triac. It defines
the triac gate current and operates as current gen-
erator. There is no need of external resistor for cur-
rent limitation.
Analog Power on Reset
This block tracks the voltage at VDDA, and permits
generation of firing pulses for the triac only if VDDA >
~13V. It is considered otherwise that the motor is not
properly supplied by the mains.
Auto Retriggering
This block tracks if the triac is on after each firing
pulse. If the triac is off 20us after a firing pulse, a
new pulse is generated.
Oscillator
There is an on chip oscillator. All timing constraints
inside the chip are derived from this clock.
Thermal Protection
The chip is able to supply an external protection cir-
cuitry, typically an NTC resistor with reference resis-
tor, to track the ambient temperature. If the voltage at
THP equals Vref/2 the protection is activated and
the chip sets the firing angle defined by the value in
ROM address 1. A resistor connected to pin FB can
introduce hysteresis in the detection level.
FLL
A frequency locked loop circuit is implemented to
obtain a clock frequency from a current controlled
oscillator, by using the mains frequency as a refer-
ence. A successive approximation algorithm is used
at start up to minimize the time for the oscillator ad-
justment.
Options
This block defines different modes of the chip opera-
tion.
Reference Voltage
This voltage is used to supply the external potenti-
ometer for the definition of different speed settings.
ADC
The analog signal from the potentiometer, which de-
fines the speed setting, is transferred into digital by a
4-bit ADC. The reference for the converter is the volt-
age used to supply the potentiometer.
Vss
90805
Voltage
regulator
Power monitoring
and reset
Vdda
ROM
The digital words from the ADC act as the address of
a ROM table in which the different firing angles are
programmed. This means that 16 different firing an-
gles can be selected.
ZCD
zero
crossing
detector
Triac driver
Auto
retriggering
SET
ADC
Lookup
ROM
Vref/2
COMP
Logic
Zero Cross
This block detects the moments when mains voltage
crosses zero level. An accurate detection allows
good synchronization, so firing pulses driving the
triac can be generated at the right moment.
Vref
Options
Vref
THP
FB
MLX90805 Intelligent Triac Controller
Page 2
Rev 1.2 17/May/00
MLX90805
Intelligent Triac Controller
MLX90805 Electrical Specifications
Environmental Conditions
Symbol
Tamb
Tch
Rth
IDDAm
Description
Ambient temperature
Maximum chip temperature
Thermal resistance
Maximum allowed source sup-
ply current
110
10
Min
0
Typ
Max
85
150
Unit
°C
°C
°C/Ω
mA
DIP8 or SOP8 package
Drivers off, all the current flows
in the chip
Condition
Analog Features
Power Supply
High voltage supply should be applied between VDDA and VSS.
Symbol
VDDA
VDD
IDDA
VREF
Description
Voltage applied at the supply
pin
Internal 5V supply
Current consumption
For external circuitry
Min
14
4.6
Typ
16
5.0
3
Max
18
5.4
Unit
V
V
mA
Condition
IDDA = 5mA
VDDA = 14V
IREF = 8mA
4.6
5
5.4
V
Power On Reset
This block ensures a correct start of the digital part.
The reset signal goes up for VDD > Vdporh and down for VDD < Vdporl.
Symbol
Vdporh
Vdporl
Vdphyst
Description
High level threshold
Low level threshold
Hysteresis
Min
Typ
2.5
2.0
0.5
Max
V
V
V
Unit
Conditions
Symbol
Vaporh
Vaporl
Vaphyst
Description
High level threshold
Low level threshold
Hysteresis
Min
12
9
2
Typ
13
10
3
Max
14
11
4
Unit
V
V
V
Condition
MLX902xx Name of Sensor
Controller
MLX90805 Intelligent Triac
Rev Y.X
3
Page
22/Aug/98
Page 3
Rev 1.2 17/May/00
MLX90805
Intelligent Triac Controller
Zero Cross Detector
This detector contains two comparators with hysteresis. The first comparator has its reference at VDDA. The
reference of the second one is VDDA-1V.
Symbol
Vzc1h
Vzc1l
Vzc2h
Vzc2l
Rzc
Description
High level threshold 1
Low level threshold 1
High level threshold 2
Low level threshold 2
External resistor
Min
Typ
VDDA
+0.5
VDDA
-0.5
VDDA
-1.5
VDDA
-2.5
470
Max
Unit
V
V
V
V
kΩ
Conditions
Vline = 230VAC typ
Triac (Ignition) Driver
This driver operates as a current generator to fire the triac ON.
Symbol
ITRG
Description
Triac gate current
Min
30
Typ
60
Max
90
Unit
mA
Conditions
VDDA > Vaporh
ADC
Symbol
Description
Resolution
VREF
Reference voltage
4.6
Min
Typ
4
5
5.4
Max
Unit
bits
V
Conditions
MLX90805 Intelligent Triac Controller
Page 4
Rev 1.2 17/May/00
MLX90805
Intelligent Triac Controller
Digital Features
Debounce of ADC
The result from the potentiometer reading must not
jump from one position to the other, therefore a spe-
cial debouncing is designed. The debounce circuit
compares the current value from the ADC with the
previous one. The new value is accepted only if the
absolute difference between the new and the previ-
ous value is greater then 1 LSB.
Firing
The soft start circuit generates a predefined set of
values for the ignition angle IGN. These values are
compared with the value of a down counter, which is
clocked by DCLK = 100kHz (the resolution is 10 us)
and is cleared at beginning of every half period of
mains. When the counter value becomes equal to
IGN the firing circuit produces an ignition pulse
GATE with duration 20us, 40us, 80us or 320us. This
duration can be chosen with option DUTS[1:0]. The
retriggering circuit checks whether the triac is ON, if
not additional firing pulses are generated every 20us
(with respect to the end of the previous firing pulse)
until firing of the triac.
Power Settings (ROM table)
The ADC output data is applied after debouncing at
the address bus of the ROM and the corresponding
power settings are available at its data output SETP
[9:0]. The content of the ROM can be defined freely:
it does not need to be linearly or continuous. When
the potentiometer setting is changed from one posi-
tion to the other, the phase angle is moved to the
new position via the soft start procedure, avoiding
abrupt changes.
For programming the different speed settings in the
ROM table, following formula can be used, given ti
(in msec) is the delay from the previous zero cross-
ing to the moment of ignition:
Thermal Protection
An external circuitry supplied by VREF defines the
voltage at pin THP. This voltage is proportional to
Tamb. It is tracked by an internal comparator re-
ferred to VREF/2. The tracking process is sampled.
When the switch is ON (see block diagram), the chip
checks if Tamb is greater than a predefined value. If
yes, the motor is driven to operate at the speed de-
fined at the first ROM address. During the time when
the switch is OFF, the chip checks what kind of mode
is defined by the external elements: 2-wire or 3-wire
potentiometer connection. A reconnection of the ele-
ments used for thermal protection is needed only to
define the active mode of operation.
The temperatures for which thermal protection be-
comes active or not are defined by the external ele-
ments, keeping in mind that comparator is referred
toVREF/2.
In the case when thermal protection is not used, pin
THP should be connected to pin FB, which is con-
nected either to Vss or to Vref, depending on the
mode.
2-wire mode, if V(FB) = VREF
3-wire mode, if V(FB) = VSS
ROMi
[9 : 0]
=
ti
•
2
•
Fmains
−
10
f.e.: for a phase angle of 50%, ti = 5msec for a 50Hz
mains, and thus:
ROMi
[ 9 : 0 ]
=
5
•
2
•
50
−
10
=
490
Note:
The value should not be negative: very small values
can not be programmed.
Soft Start
The soft start is initiated after the supply voltage has
been built up. This behavior guarantees a gentle
start-up for the motor and automatically ensures the
optimum run-up time. The motor is fired initially with
a very small phase angle, i.e. a delay time very
close to half the mains period. The phase angle is
than increasing up to the phase angle defined by the
potentiometer setting. The rate of increase is defined
by the option ATN[4:0]. This option defines the time
to increase the phase angle from minimum to maxi-
mum. If the phase angle, selected by the potentiome-
ter, is not the maximum phase angle then the soft
start run-up time is decreased proportionally.
MLX902xx Name of Sensor
Controller
MLX90805 Intelligent Triac
Rev Y.X
5
Page
22/Aug/98
Page 5
Rev 1.2 17/May/00
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