TEA1530T_AT_AP_1

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 01 — 30 June 2008

8 of 21

NXP Semiconductors

TEA1530T/AT/AP

GreenChip II SMPS control IC

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

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:

regulation (e.g. the control loop is open). In this case activating pin PROTECT

be repeated until the fault condition is removed (safe restart mode).

Fig 6.

Slope compensation

014aaa255

CTRL

−1

0.63 V

control

detect

5.6 V

4

RCTRL

Rslopecomp

∆Isc/∆t