tea1553t NXP Semiconductors, tea1553t Datasheet - Page 13

• Manufacturer Part Number: tea1553t
• Description: Tea1553t Greenchip Ii Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1553T_1
Product data sheet
7.13 Advanced overpower timing via pin CSTART
The OPP curve is given in
Overload conditions might lower the switching frequency below 20 kHz, since
demagnetization prevents next cycle occurrence before the transformer current reaches
zero (demagnetization protection). To prevent audible noise, an extra timer of typically
25 kHz is added. When the timer is activated (the frequency is typically below 25 kHz), a
current (I
capacitor. The current that is being injected is dependent on the V
duty cycle, see also
The current injection results in a decrease of the primary peak current and a higher
frequency. The injection is only possible when the voltage on the control pin is below 0.5 V
and the CSTART voltage is above 2.5 V. The current injection is disabled when
V
start-up (CSTART timing) and when V
Fig 10. OPP correction curve
Fig 11. I
CTRL
> 0.5 V (that is, in normal operation and also in frequency reduction mode), during
AOP
AOP
) of approximately 10 A is injected into the external soft-start resistor and
as a function of V
500 A
(TYP)
Figure 11
Rev. 01 — 3 July 2007
Figure
7.5
I
( A)
AOP
10
SENSE
5
and
10.
Figure
I
DEM
SENSE
12.
0.5
> 0.5 V.
~ 50%
~ 0%
120 A
(TYP)
V
SENSE(V)
014aaa010
GreenChip II SMPS control IC
V
0.52 V
(TYP)
0.30 V
(TYP)
sense(max)
014aaa009
SENSE
TEA1553T
© NXP B.V. 2007. All rights reserved.
voltage and the
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