SX8124ISTRT SEMTECH [Semtech Corporation], SX8124ISTRT Datasheet - Page 17

• Manufacturer Part Number: SX8124ISTRT
• Description: 24 hours timer synchronized on 50/60Hz mains
• Manufacturer: SEMTECH [Semtech Corporation]

ACS - Revision 2.4
© Semtech Corp.
APPLICATION EXAMPLES
11
ADVANCED COMMUNICATIONS & SENSING
Complete application schematics
The circuit can be directly powered from the mains through a diode bridge and a resistor as long as the
supply voltage is limited at ~1.2V by diodes or similar devices. The choice of the resistor that limits the supply
current must be made so that it delivers enough current for the system to supply the IC and any other device
that is connected to that supply, but the resistor must be large enough to limit the current in sleep mode (120
kOhm will limit power dissipation below 0.3W on a 220V network).
The RC filter on the power supply is there to reject 100 Hz or 120 Hz variations.
The phase detector is used to increase the precision on the 24 hours counter. It is recommended to protect
the pin with external diodes. The filter on the phase detector is there to reject high frequency perturbations
(several kHz) but must let the 50 Hz or 60 Hz go through with limited attenuation.
The timer element is a potentiometer. The total resitivity of the potentiometer must be low enough to avoid
sensitivity to the DURATION pin impedance (> 500 kOhm) and high enough to limit current drift current. The
voltage applied on the potentiometer is 1/100 of the voltage applied on the resistor that protects the supply
voltage of the chip, therefore the current through these resistors will be in the same ratio if they have the
same value.
The power element (either a resistove heater for a diffuser or a motor for a ventilator) will be controlled
through an NPN transistor.
200 V supply
91 kOhm
200V
3.9 MOhm
Figure 18. Application schematics with low-power sleep mode (below 0.3 W)
91 kOhm
50 uA
200V
October 2010
1.5 – 2.0 V supply
0Ohms
1.2 V
1.5 mA
Page 17
DURATION
PHASE
START
LED
24 hours timer synchronized on 50/60Hz mains
SX8124
BURST GEN
DEBOUNCE
SYNC
ADC
NOUT
VDD
OUT
VSS
www.semtech.com/products/
1 kOhm
500 uA
SX8124
DATASHEET
15 kOhm
11 W Heater
MSPA44
W < 300 mW
IC < 300 mA
B = 50
VC < 300 V
VB < 6V
25 mA