TEA1532T Philips Semiconductors, TEA1532T Datasheet - Page 8

• Manufacturer Part Number: TEA1532T
• Description: GreenChip SMPS control IC
• Manufacturer: Philips Semiconductors

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Product data sheet
7.11 Minimum and maximum on-time
7.12 PROTECT and timing input
on-time. Slope compensation can be adjusted by changing the value of R
compensation prevents modulation of the on-time (duty cycle) while operating in FF CCM.
A possible drawback of sub-harmonic oscillation can be output voltage ripple.
The source current of pin CTRL is always active. In QR mode, the R
replaced by a short, so the modulation of the CTRL voltage is almost negligible.
The minimum on-time of the SMPS is determined by the LEB time (typical 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, the IC stops switching and enters the safe restart mode.
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 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 A MOSFET switch is added to discharge
the external capacitor and ensure a defined start situation. For the TEA1532AP and the
TEA1532AT, 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
Rev. 02 — 4 February 2005
R
CTRL
TEA1532(A)P; TEA1532(A)T
R
slopecomp
CTRL
4
GreenChip II SMPS control IC
Slope compensation
current
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
0.63 V
001aaa830
5.6 V
control
detect
1
slopecomp
slopecomp
resistor is
. Slope
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