AN10907
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© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1 — 28 December 2010
24 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
6.6.2 Value of the capacitor on SUPREG
To support charging of SUPREG during an HV source start, the capacitor on SUPREG
should not be larger than the capacitor on SUPIC. This is to prevent a severe voltage drop
on SUPIC due to the charge of SUPREG. If SUPIC is supplied by an external (standby)
source, this is not important.
SUPREG is the supply for the current of the gate drivers. Keeping current peaks local can
be achieved using an SMD ceramic capacitor which is supported by an electrolytic
capacitor. This is necessary to provide sufficient capacitance to prevent voltage drop
during high current loads. The value of the capacitor on SUPREG should be much larger
than the total capacitance of the MOSFETs that need to be driven (including the load and
capacitor on SUPHS that is in parallel with the bootstrap construction), to prevent
significant voltage drop.
When considering the internal voltage regulator, the value of the capacitance on SUPREG
should be
1
F to ensure basic regulation properties. Often a much larger value is used
for the reasons mentioned previously.
6.6.3 Value of the capacitor for SUPHS
To support charging the gate of the high side MOSFET, the SUPHS capacitor should be
much larger than the gate capacitance. This prevents a significant voltage drop on
SUPHS by the gate charge. When burst mode is applied, SUPHS is discharged by 37
A
during the time between two bursts by the quiescent current of the internal circuit.
6.6.4 Relationship between the capacitors on SUPIC, SUPREG and SUPHS
It can be generally stated that:
•
C
SUPIC
> C
SUPREG
> C
SUPHS
•
In a system that uses burst mode operation, the capacitor values need to be larger
than in a system without burst mode operation
