TEA1532CT NXP Semiconductors, TEA1532CT Datasheet - Page 9

• Manufacturer Part Number: TEA1532CT
• Description: (TEA1532BT / TEA1532CT) GreenChip II SMPS control IC
• Manufacturer: NXP Semiconductors

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NXP Semiconductors
TEA1532BT_TEA1532CT_1
Product data sheet
7.11 Minimum and maximum on-time
7.12 Soft start-up (pin SENSE)
value of R
while operating in FF CCM. A possible drawback of sub-harmonic oscillation can be
output voltage ripple.
The minimum on-time of the SMPS is determined by the Leading Edge Blinking (LEB)
time (typically 400 ns). The IC limits the on-time to a maximum time, which is dependent
on the mode of operation:
QR mode: When the system requires an ‘on-time’ of more than 25 s, a fault condition is
assumed (e.g. C
CCM: The driver duty cycle is limited to 70 %. So the maximum on-time is correlated to
the oscillator time, which results in an accurate limit of the minimum input voltage of the
flyback converter.
To prevent transformer rattle at start-up or during hiccup, the transformer peak current is
slowly increased by the soft start function. This can be achieved by inserting a resistor
and a capacitor between pin SENSE (pin 6) and sense resistor R
source charges the capacitor to V
The start level and the time constant of the increasing primary current level can be
adjusted externally by changing the values of R
I
DM
Fig 7. Slope compensation
=
R
=
ss
V
-------------------------------------------------------------------------------------- -
sense max
C
slopecomp
ss
VCC
. Slope compensation prevents modulation of the on-time (duty cycle)
–
removed). The IC stops switching and enters the safe restart mode.
R
Rev. 01 — 18 January 2007
I
sense
startup soft
R
CTRL
SENSE
R
R
TEA1532BT; TEA1532CT
sc
ss
= I
startup(soft)
CTRL
ss
4
and C
R
ss
ss
slope compensation
current
.
GreenChip II SMPS control IC
(about 0.5 V maximum).
0.63 V
001aaa830
5.6 V
control
detect
sense
1
. An internal current
© NXP B.V. 2007. All rights reserved.
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