Datasheet

TEA1721FT All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 1.1 — 7 June 2012 6 of 14
NXP Semiconductors
TEA1721FT
HV start-up flyback controller with integrated MOSFET for 5 W
5.3.3 Constant Current mode (CC)
The CC mode starts at maximum power delivery and keeps the output current constant for
decreasing output voltage.
CC mode is enabled when the converter is operating at the maximum switching
frequency, with the maximum primary peak current when the FB voltage drops below the
regulated level.
CC mode operation controlled is by regulation of the switching frequency from 50.5 kHz
down to 22.5 kHz and by I
SOURCE
regulation from the maximum V
SOURCE
level of 555 mV
until level of V
SOURCE
is 0.21 V. The V
SOURCE
level of 0.21 V equals the level at start-up
with zero output voltage and the output capacitor discharged or on a short-circuit of the
charger output.
5.4 Jitter
The TEA1721 features a jitter function for ElectroMagnetic Interference (EMI) reduction.
The switching frequency is 7 % typical for the spread spectrum. The sweep frequency is a
low frequency of approximately 200 Hz. To keep the output power constant, the V
SOURCE
level is jittered with the opposite polarity. The jitter is active in all operation modes except
burst mode.