TEA2019 Просмотр технического описания (PDF) - STMicroelectronics
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TEA2019 Datasheet PDF : 7 Pages
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TEA2019
• Efficient and fast switch-off
When the positive base drive is removed, 1s
(typically) will elapse before the application of
negative current therefore allowing a safe and
rapid collector current fall.
Safety Functions
• Overload & short-circuit protection
When the voltage applied to pin 12 exceeds the
current limitation thershold voltage [Vth(Ic)], the
output flip-flop is reset and the transistor is turned
off.
The shunt resistor Re must be calculated so as
to obtain the current limitation threshold on pin
12 at the maximum allowable collector current.
Figure 2
• Demagnetization sensing
This function disables any new conduction cycle
of the transistor as long as the core is not com-
pletely demagnetized.
When not used, pin 5 must be grounded.
• ton(max)
Outside the regulation area and in the absence
of current limitation, the maximum conduction
time is set at about 70% of the period.
• ton(min)
A minimum conducting time is ensured during
each period (see Figure 2).
• Supply voltage monitoring
The TEA2019 will stop operatingif VCC+ on Pin 3
falls below the threshold level VCC(stop).
IC
TEA2019
12
IC
RB
1
IB
Re
0
IB
t on(min)
0
COLLECTOR
CURRENT IC
t
BIAS
CURRENT
IB
RB
Re
IC
t
Starting Process (Figure 3)
Prior to starting, a low current is drawn from the
high voltage source through a high value resistor.
This current charges the power supply storage
capacitor of the device.
No output pulses are available before the voltage
on pin 3 has reached the threshold level [VCC(start),
V+CC rising].
During this time the TEA2019 draws only 1mA
(typically). When the voltage on pin 3 reaches this
threshold base drive pulses appear.
The energy drawn by these pulses tends to dis-
charge the power supply storage capacitor. How-
ever a hysteresis of about 1.1V (typically) (∆ VCC)
is implemented to avoid the device from stopping.
Figure 3 : Normal TEA2019 Start up Sequence
V CC
6V
V CC
4.9V
VCC (start)
VCC (stop)
t
5/7
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