TEA1533T Ver la hoja de datos (PDF) - Philips Electronics
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Fabricante
TEA1533T Datasheet PDF : 24 Pages
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Philips Semiconductors
GreenChipTMII SMPS control IC
Product specification
TEA1533T; TEA1533AT
Soft start-up
To prevent transformer rattle 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 Isense and the sense resistor
(see Fig.10). An internal current source charges the
capacitor to V = ISS × RSS, with a maximum of
approximately 0.5 V.
The start level and the time constant of the increasing
primary current level can be adjusted externally by
changing the values of RSS and CSS.
Iprimary(max) = V-----o--c---p----–--R--(--sI--S-e--nS---s--×e-----R----S---S----)
τ = RSS × CSS
The charging current ISS will flow as long as the voltage on
pin Isense is below approximately 0.5 V. If the voltage on
pin Isense exceeds 0.5 V, the soft start current source will
start limiting the current ISS. At the VCC(start) level, the ISS
current source is completely switched off.
Since the soft start current ISS is subtracted from pin VCC
charging current, the RSS value will affect the VCC charging
current level by a maximum of 60 µA (typical value).
Driver
The driver circuit to the gate of the power MOSFET has a
current sourcing capability of 170 mA typical and a current
sink capability of 700 mA typical. This permits fast turn-on
and turn-off of the power MOSFET for efficient operation.
A low driver source current has been chosen to limit the
∆V/∆t at switch-on. This reduces Electro Magnetic
Interference (EMI) and also limits the current spikes
across Rsense.
handbook, halfpage
0.5 V
ISS
start-up
9 Isense RSS
Vocp
CSS
Fig.10 Soft start.
Rsense
MGU502
2002 Aug 23
11
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