U2010B_10 Datasheet, PDF (4/18 Pages) ATMEL Corporation – Programmable Load-current Limitation with Over- and High-load Output

3. General Description
3.1 Mains Supply
The U2010B contains voltage limiting and can be connected with the mains supply via D₁ and
R₁. Supply voltage – between pin 10 and pin 11 – is smoothed by C₁.
In the case of V₆ ≤ 70% of the overload threshold voltage, pins 11 and 12 are connected inter-
nally whereby V_sat ≤ 1.2 V. When ⏐ V₆⏐ ≥ ⏐ V_T70⏐ , the supply current flows across D₃.
The series resistance R₁ can be calculated as follows:
R_1max = ^V-----^m----^a--₂ⁱ-ⁿ---^s-_×---–---_I-^V-_t-_o--^St---^m----^a---^x-
where:
V_mains
V_Smax
I_tot
I_Smax
I_x
= Mains supply voltage
= Maximum supply voltage
= Total current consumption = I_Smax + I_x
= Maximum current consumption of the IC
= Current consumption of the external components
3.2 Voltage Monitoring
When the voltage is built up, uncontrolled output pulses are avoided by internal voltage monitor-
ing. Apart from that, all latches in the circuit (phase control, load limit regulation) are reset and
the soft-start capacitor is short-circuited. This guarantees a specified start-up behavior each time
the supply voltage is switched on or after short interruptions of the mains supply. Soft start is ini-
tiated 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.
3.3 Phase Control
The function of the phase control is mainly identical to the well-known IC U211B. The phase
angle of the trigger pulse is derived by comparing the ramp voltage V₃, which is mains-synchro-
nized by the voltage detector, with the set value on the control input, pin 4. The slope of the
ramp is determined by Cϕ and its charging current Iϕ. The charging current can be varied using
Rϕ at pin 14. The maximum phase angle, α_max, can also be adjusted by using Rϕ (minimum cur-
rent flow angle ϕmin), see Figure 7-1 on page 10.
When the potential on pin 3 reaches the set point level of pin 4, a trigger pulse width, t_p, is deter-
mined from the value of Cϕ (t_p = 9 µs/nF). At the same time, a latch is set with the output pulse
as long as the automatic retriggering has not been activated. When this happens, no more
pulses can be generated in that half cycle. The control input at pin 4 (with respect to pin 10) has
an active range from V₈ to -1 V. When V₄ = V₈, then the phase angle is at its maximum, α_max, i.e.,
the current flow angle is minimum. The minimum phase angle, α_min, is set with V₄ ≥ -1 V.
4 U2010B
4766C–INDCO–04/10