U2102B Datasheet, PDF (5/19 Pages) TEMIC Semiconductors – Multifunction Timer

U2102B
3. Power Supply, Synchronization Pins 15 and 16
The U2102B’s voltage limitation circuit enables the power supply via the dropping resistor R₁. In
the case of DC loads, the entire supply current flows into pin 16 and is supplied via an internal
diode to pin 15, where the resultant supply voltage is limited and smoothed by C₁. The pull-down
resistor at pin 16 is necessary in order to guarantee reliable synchronization. As a result, the rec-
tified and divided line voltage appears at pin 16, where the amplitude is limited. The power
supply for the circuit can be realized in all modes for DC loads as shown in Figure 2-2 on page 4.
The voltage at pin 16 is used to synchronize the circuit with the mains and generate the system
clock required for the buffers. The circuit detects a “zero crossing” when the voltage at pin 16
falls below an internal threshold of approximately 8 V.
Figure 3-1. Power Supply for DC Loads (R₁ is Identical with R_sync)
Sync.
16
Voltage
limitation
+V_S
15
Push
pull
14
Temp.
monit.
GND
13
R₁ = R_sync
V_mains
Load
C₁
IGBT
R_G
R_sh
R₁ is calculated as follows:
R_1max
=
0.85 ×
V_{-----N---m----i-n----–-----}V_----S-
I_tot
where:
V_Nmin = V_mains – 15%
V_S = Supply voltage
I_tot = I_Smax + I_x
I_Smax = Maximum current consumption of the IC
I_x = Current consumption of the external components
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4767B–INDCO–10/05