tea1553t NXP Semiconductors, tea1553t Datasheet - Page 9

• Manufacturer Part Number: tea1553t
• Description: Tea1553t Greenchip Ii Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1553T_1
Product data sheet
7.6 Cycle skipping
7.7 STDBY output
At very low power levels, a cycle skipping mode will be activated. A high control voltage
will reduce the switching frequency to a minimum of 25 kHz. If the voltage on the control
pin is raised even more, switch-on of the external power MOSFET will be inhibited until the
voltage on the control pin has dropped to a lower value again (see
For system accuracy, the absolute voltage on the control pin is not used to trigger the
cycle skipping mode. Instead, a signal derived from the internal VCO will be used.
If the no-load requirement of the system is such that the output voltage can be regulated
to its intended level at a switching frequency of 25 kHz or above, the cycle skipping mode
will not be activated.
The STDBY output pin can be used to drive an external NPN or FET, V
order to switch off a Power Factor Correction (PFC) circuit. The STDBY output is activated
by the internal VCO: as soon as the VCO has reduced the switching frequency to almost
the minimum frequency of 25 kHz, the STDBY output will be activated (see
STDBY output will go low again as soon as the VCO allows a switching frequency close to
the maximum frequency of 125 kHz.
Fig 8. Signal diagram for STDBY and cycle skipping functionality
(1) The voltage levels dV
40 mV (typ.) and 15 mV (typ.) respectively. The level at which the VCO mode of operation
starts/ends can be externally controlled with the VCOADJ pin.
CYCLE SKIPPING
STDBY (V)
f
s
f
f
max
min
(kHz)
“1”
“0”
Rev. 01 — 3 July 2007
5
0
1
, dV
2
, dV
3
and dV
dV
2
4
are fixed in the IC to 50 mV (typ.), 18 mV (typ.),
dV
dV
1
3
dV
VCOADJ
4
GreenChip II SMPS control IC
Vx (V)
Vx (V)
Vx (V)
014aaa007
Figure
TEA1553T
© NXP B.V. 2007. All rights reserved.
STDBY
8).
Figure
= 5 V, in
8). The
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