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EA1530T

GreenChip II SMPS control IC

NXP Semiconductors. 

NXP Semiconductors

TEA1530T/AT/AP

GreenChip II SMPS control IC

Rslopecomp CTRL 4

RCTRL

∆Isc/∆t

−1

5.6 V

control

detect

0.63 V

Fig 6. Slope compensation

014aaa255

7.10 Minimum and maximum on-time

The minimum on-time of the SMPS is determined by the LEB time (typically 400 ns). The

IC limits the maximum on-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 multipurpose, 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. An internal MOSFET switch is added to

discharge the external capacitor and ensures a defined start situation. For the

TEA1530AP and TEA1530AT 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

Vth(UVLO), 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 Vstartup and Vth(UVLO), but the IC will not start switching again until the latch

TEA1530T_AT_AP_1

Product data sheet

Rev. 01 — 30 June 2008

© NXP B.V. 2008. All rights reserved.

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