TEA1532 Philips Semiconductors, TEA1532 Datasheet - Page 8

• Manufacturer Part Number: TEA1532
• Description: GreenChip SMPS control IC
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 13113
Preliminary data sheet
7.11 Minimum and maximum on-time
7.12 PROTECT and timing input
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 LEB time. 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.
The PROTECT input (pin 3) is a multi-purpose (high-impedance) input, which can be used
to switch off the IC and create a relatively long timing function. As soon as the voltage on
this pin rises above 2.5 V, switching stops immediately. For the timing function, a current of
typically 50 A flows out of pin PROTECT and charges an external capacitor until the
activation level of 2.5 V is reached. This current source however, is only activated when
the converter is not in regulation, which is detected by the voltage on pin CTRL
(V
capacitor is not charged, for example, by spikes, and a MOSFET switch is added to
ensure a defined start situation. The voltage on pin CTRL determines whether the IC
enters latched protection mode, or safe restart protection mode:
Fig 7. Slope compensation.
CTRL
< 0.63 V). A (small) discharge current is also implemented to ensure that the
slopecomp
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 — 28 May 2004
CTRL
R
slopecomp
CTRL
4
TEA1532
GreenChip II SMPS control IC
Slope compensation
current
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
0.63 V
001aaa830
5.6 V
control
detect
1
TEA1532
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