TEA1721AT Datasheet, PDF (5/14 Pages) NXP Semiconductors – Ultra-low standby SMPS controller with integrated power switch

NXP Semiconductors
TEA1721AT
Ultra-low standby SMPS controller with integrated power switch
5.3 Operating modes
The TEA1721 operates in three modes, one of which is active at the time. The three
modes in order of decreasing load impedance are:
• CVB: Constant Voltage with Burst mode
• CV: Constant Voltage mode
• CC: Constant Current mode
The converter acts as a voltage source in CVB and CV modes.
The converter acts as a current source in CC mode.
5.3.1 Constant Voltage with Burst mode (CVB)
At low power, the TEA1721 operates in Burst mode.
Burst mode operates with a V_SOURCE = 100 mV, a switching frequency of 22.5 kHz and
burst duty-cycle regulation by sensing the FB voltage.
The TEA1721 features an energy save function that puts the main part of the analogue
blocks in a sleep mode with low supply current in burst mode. The burst mode enables the
energy save mode in the non-switching part of the burst. The IC switches to the nominal
supply just before new burst starts.
Transition from burst mode to CV mode happens at 100 % burst duty cycle: a burst
completely filled with 32 pulses. This 100 % pulse train is identical to the lowest power
level of the CV mode. The TEA1721 changes directly from burst mode to current mode if
the FB voltage drops below 2.4 V in burst mode.
5.3.2 Constant Voltage mode (CV)
At higher power levels, the TEA1721 operates in CV mode. The output voltage is sensed
by the FB pin and the control keeps the output voltage constant over the power range.
CV mode starts at 22.5 kHz switching frequency and I_SOURCE regulation at the V_SOURCE
minimum level of 100 mV.
With an increasing power output, the V_SOURCE level and the switching frequency are also
increased.
CV mode is exited when the maximum power level is reached. Maximum power occurs at
I_SOURCE regulation at the V_SOURCE maximum level of 555 mV and a maximum switching
frequency of 50.5 kHz.
TEA1721AT
Preliminary data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 24 January 2012
© NXP B.V. 2012. All rights reserved.
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