TEA1532BT_TEA1532CT_1

© NXP B.V. 2007. All rights reserved.

Product data sheet

Rev. 01 — 18 January 2007

9 of 23

NXP Semiconductors

TEA1532BT; TEA1532CT

GreenChip II SMPS control IC

while operating in FF CCM. A possible drawback of sub-harmonic oscillation can be

output voltage ripple.

7.11 Minimum and maximum on-time

The minimum on-time of the SMPS is determined by the Leading Edge Blinking (LEB)

time (typically 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

µs, a fault condition is

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.

7.12 Soft start-up (pin SENSE)

To prevent transformer rattle at start-up or during hiccup, the transformer peak current is

slowly increased by the soft start function. This can be achieved by inserting a resistor

The start level and the time constant of the increasing primary current level can be

Fig 7.

Slope compensation

001aaa830

CTRL

−1

slope compensation

current

0.63 V

control

detect

5.6 V

4

I

DM

V

sense max

)

(

I

startup soft

)

(

R

ss

×)

(

–

R

sense

---------------------------------------------------------------------------------------

=

τ

R

ss

C

ss

×

=