U211B-XFPG3Y ATMEL Corporation, U211B-XFPG3Y Datasheet - Page 5

• Manufacturer Part Number: U211B-XFPG3Y
• Description: Phase Control IC with Overload Limitation for Tacho Applications
• Manufacturer: ATMEL Corporation

5. Voltage Monitoring
6. Soft Start
4752B–INDCO–09/05
As the voltage is built up, uncontrolled output pulses are avoided by internal voltage surveil-
lance. At the same time, all latches in the circuit (phase control, load limit regulation, soft start)
are reset and the soft-start capacitor is short circuited. Used with a switching hysteresis of
300 mV, this system guarantees defined start-up behavior each time the supply voltage is
switched on or after short interruptions of the mains supply.
As soon as the supply voltage builds up (t
shows the behavior of the voltage across the soft-start capacitor, which is identical with the volt-
age on the phase-control input on pin 12. This behavior guarantees a gentle start-up for the
motor and automatically ensures the optimum run-up time.
Figure 6-1.
C
the charging current to approximately 4 µA, the slope of the charging function is also substan-
tially reduced, so that the rotational speed of the motor only slowly increases. The charging
current then increases as the voltage across C
charging function which accelerates the motor more and more with increasing rotational speed.
The charging function determines the acceleration up to the set point. The charging current can
have a maximum value of 55 µA.
3
is first charged up to the starting voltage V
Soft Start
V
V
V
12
C3
0
t
1
t
t
t
t
t
1
2
1
3
tot
= Build-up of supply voltage
= Charging of C
+ t
= Run-up time
= Total start-up time to required speed
t
2
2
= Dead time
1
), the integrated soft start is initiated.
0
t
with a current of typically 45 µA (t
tot
3
3
to starting voltage
increases, resulting in a progressively rising
t
3
t
2
). By reducing
U211B
Figure 6-1
5