MLX90805 ETC [List of Unclassifed Manufacturers], MLX90805 Datasheet - Page 9

• Manufacturer Part Number: MLX90805
• Description: Intelligent Triac Controller
• Manufacturer: ETC [List of Unclassifed Manufacturers]

Soft Start With 2-Wire Setting
The speed control is performed in addition to the soft
start in this application. A potentiometer in 2-wire
connection is used to define different speed settings.
An additional resistor RP with value equal to the po-
tentiometer is used to keep the ADC input to be ra-
tiometric. In this case, the input signal for the ADC
varies between 0 and VREF/2.
The minimum speed corresponds to a potentiometer
set to its minimum value (i.e. Rpot = 0). Maximum
speed corresponds to a potentiometer set to its maxi-
mum value. When the mains voltage is applied to the
system, the motor starts running at a speed defined
by the potentiometer, as soon as the soft start time
has finished.
The disadvantage of the 2-wire application is that, at
maximum speed setting, the tolerance on the abso-
lute value of the potentiometer defines the tolerance
of the voltage at the SET input, resulting in a less
accurate selection of the maximum speed setting.
This can be avoided when using the 3-wire applica-
tion.
The voltage at SET is transferred to a 4 bit value to
address a ROM table in which the different phase
angles are defined with a 10 bit resolution.
The 2-wire mode is selected by connecting VFB to
VREF (eventually via a resistor).
MLX902xx Name of Sensor
MLX90805 Intelligent Triac Controller
Applications Example - Soft Start with 2-Wire Setting
N
L
Cf
R Z
R M
Z C
Vdda
Vss
T H P
Rev Y.X
N T C
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R2
Note:
R1, R2 and NTC are only needed for thermal pro-
tection, and can be left out otherwise
90805
Vref
R P
R1
Intelligent Triac Controller
FB
S E T
22/Aug/98
T R G
Pot
MLX90805
Rev 1.2 17/May/00
M
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