Q67000-A9284-X201-K5 데이터 시트보기 (PDF) - Infineon Technologies
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Q67000-A9284-X201-K5 Datasheet PDF : 39 Pages
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TDA 16888
Both PFC and PWM section are equipped with a peak current limitation, which is realized
by the comparators C3 and C9 sensing at pin 6 (PFC CL) and pin 11 (PWM CS)
respectively. When being activated this current limitation will immediately shut down the
respective gate drive PFC OUT (pin 8) or PWM OUT (pin 10).
Finally each pin is protected against electrostatic discharge.
Oscillator/Synchronization
The PFC and PWM clock signals as well as the PFC voltage ramp are synchronized by
the internal oscillator (see Figure 18). The oscillator’s frequency is set by an external
resistor connected to pin 16 (ROSC) and ground (see Figure 5). The corresponding
capacitor, however, is integrated to guarantee a low current consumption and a high
resistance against electromagnetic interferences. In order to ensure superior precision
of the clock frequency, the clock signal CLK OSC is derived from a triangular instead of
a saw-tooth signal. Furthermore to provide a clock reference CLK OUT with exactly 50%
duty cycle, the frequency of the oscillator’s clock signal CLK OSC is halved by a D-latch
before being fed into the PFC and PWM section respectively (see Figure 18).
The ramp signal of the PFC section VPFC RMP is composed of a slowly falling and a
steeply rising edge. This ramp has been reversed in contrast to the common practice, in
order to simultaneously allow for current measurement at pin 5 (GND S) and for external
compensation of OP2 by means of pin 5 (GND S) and pin 3 (PFC CC).
The oscillator can be synchronized with an external clock signal supplied at pin 12
(SYNC). However, since the oscillator’s frequency is halved before being fed into the
PFC and PWM section, a synchronization frequency being twice the operating frequency
is recommended. As long as the synchronization signal is H the oscillator’s triangular
signal VOSC is interrupted and its clock signal CLK OSC is H (see Figure 19 and
Figure 20). However, as soon as the external clock changes from H to L the oscillator is
released. Correspondingly, by means of an external clock signal supplied at pin 12
(SYNC) the oscillator frequency fOSC set by an external resistor at pin 16 (ROSC) can be
varied on principle only within the range from 0.66 fOSC to 2 fOSC. If the oscillator has to
be synchronized over a wider frequency range, a synchronization by means of the sink
current at pin 16 (ROSC) has to be preferred to a synchronization by means of pin 12
(SYNC). Anyhow, please note, that pin 12 (SYNC) is not meant to permanently
shutdown both PFC and PWM section. It can be used to halt the oscillator freezing the
prevailing state of both drivers but does not allow to automatically shut them down. A
shutdown can be achieved by shorting pin 2 (VREF) to ground, instead.
Finally, In order to reduce the overall current consumption under low load conditions, the
oscillator frequency itself is halved as long as the voltage at pin 13 (PWM SS) is less
than 0.4 V (disabled PWM section).
Data Sheet
7
2000-02-28
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