Pin 3
TR
Trigger and Turn-off Output
This pin realizes three functions:
• Delivery of trigger pulses with a repetition instalment of 960 µs, a pulse width of 1 µs and a current flow of
600 mA with 10
Ω resistance.
• Monitoring of the control signals up to a frequency of 100 kHz and a minimum amplitude of 400 mV. The
oscillation detector gates trigger pulses, if a minimum three periode burst indicated during the trigger pulse
repetition rate.
• Attenuation of the oscillations by a turn-off transistor with a low saturation voltage.
Negative pulses may be applied at pin TR according the specification. Negative voltage peaks can cause an
increase of the current consumption. An external Schottky diode between TR and ground prevents this.
Pin 4
GND
Connection to ground
Pin 5
EI
Error Indication
At pin 5 it is possible to indicate different error values.
A static error signal greater than 250 mV, which is supplied by a suitable network at pin 5 releases after one
second by means of an error enquiry cycle the storage of the error.
Furthermore the IC allows to supervise high-frequency oscillations.
An elaborate enquiry routine has been set up for secure and reliable acquisition of errors under consideration of
distortions. This routine consists of the valuation time of 840 µs with following evaluation time of 120 µs. These two
periods make the enquiry cycle repeating continuously, when no error signal is stored.
Signals with an amplitude > 250 mV and a minimum duration of 1 µs are valuated as errors. If such events happen
at least 4 times within a time window of 840 µs, or a level > 250 mV is statically applied, a counter starts to realize
a delay time of one second.
If those signals are detected again in the following valuation cycle, the error memory is setted.
This enquiry system saves that the RF-amplitude of the oscillating frequency is supervised, so that feed backs of
damaged lamps on the oscillation circuit would be detected. A valuation threshold of 250 mV is choiced because
of the low ohmic sense resistor, i.g. the emitter resistor of the ground connected switching transistor.
The kind of lamp damage is depending on the type and sample of lamp. That is the reason for an adaptive
network for error detection, therefore the input EI is universal applicable.
Pin 6
LW
Input of Lamp Change
This input serves to detect a lamp change and cause a re-start with simultaneous reset of the error memory.
Input LW detects whether a lamp is connected, when a voltage > 4.25 V is applied.
A voltage < 3.25 V indicates a lamp as removed.
Is a lamp exchanged after a stored error, the error memory is reset and the trigger stop is activated.
The circuit is blocked without lamp. By removal a lamp the trigger gate is opened.
With a normal lamp change under operational conditions, triggers are continuously generated with lamp removed,
therefore, the circuit starts oscillation immediately by exchange of lamp.
The switching level for lamp change will be provided by a special circuitry.
For internal testing purposes at the input LW will be applied a special test level that decreases the internal time
response by factor 16.
This divider factor is active, if VLW is more than 2 V above VCC, but limited by max.15 V. Pay attention that the
voltage difference between VCC and VLW do not has to increase above 6 V also in case of supply voltage break
down.
Pin 7
S
Switching Output
The switching output enables the control of the preheat duration of the coiled filament by means of an additional
circuit to be selected by the customer.
The switching output is an open collector output which is low active for one second during the phase of start. It is
able to drive a maximum current of 1 mA at a typical saturation voltage of 200 mV.
4
09/00
TFA3351
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
