TEA1530AT データシートの表示（PDF） - Philips Electronics
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TEA1530AT Datasheet PDF : 22 Pages
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Philips Semiconductors
TEA1530AT
GreenChip™II SMPS control IC
Slope compensation
current
Rslopecomp CTRL 4
RCTRL
−1
5.6 V
control
detect
0.63 V
Fig 6. Slope compensation
001aaa830
7.10 Minimum and maximum on-time
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 by limiting the driver duty cycle 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
7.11 PROTECT and timing input
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 µA 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
(VCTRL < 0.63 V). A (small) discharge current is also implemented to ensure that the
capacitor is not charged, for example, by spikes. A MOSFET switch is added to discharge
the external capacitor and ensure a defined start situation. The voltage on pin CTRL
determines whether the IC enters latched protection mode, or safe restart protection
mode:
• When the voltage on pin CTRL is below 0.63 V, the IC is assumed to be out of
regulation (e.g. the control loop is open). In this case activating pin PROTECT
(VPROTECT > 2.5 V) will cause the converter to stop switching. Once VCC drops below
VUVLO, capacitor CVCC will be recharged and the supply will restart. This cycle will be
repeated until the fault condition is removed (safe restart mode).
• When the voltage on pin CTRL is above 0.63 V, the output is assumed to be in
regulation. In this case activating pin PROTECT (VPROTECT > 2.5 V), by external
means, will activate the latch protection of the IC: The voltage on pin VCC will cycle
between Vstart and VUVLO, but the IC will not start switching again until the latch
Objective data sheet
Rev. 01 — 18 May 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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