NXP Semiconductors AN10907, Application Note

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AN10907 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
Application note Rev. 1 — 28 December 2010 62 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
10.3.3.2 OVP functionality and UVP disabled
In some applications it may be required to prevent the activation of the UVP on
SNSOUT/PFCON. To achieve this, it is necessary to disable UVP. This can be realized by
adding a circuit that prevents the voltage on SNSOUT from dropping below 2.35 V.
Practical example
The voltage on SNSOUT/PFCON can be prevented from dropping below a preset voltage
by externally adding a low impedance resistor divider, with a fixed voltage, and connecting
it to SNSOUT/PFCON via a diode. This simple circuit is not very accurate but it does
provide the basic capability to disable the UVP function of SNSOUT/PFCON. Note that
higher voltages on SNSOUT/PFCON are blocked by the diode so that the OVP is still
functional.
10.3.3.3 UVP functionality and OVP disabled
In some applications it may be required to prevent the activation of the OVP on
SNSOUT/PFCON. To achieve this, it is necessary to disable OVP. This can be realized by
adding a circuit that prevents the voltage on SNSOUT/PFCON from exceeding 3.5 V.
Practical example
The voltage on SNSOUT/PFCON can be prevented from exceeding the preset voltage by
externally adding a low impedance resistor divider, with a fixed voltage, and connecting it
to SNSOUT/PFCON via a diode denoted by (1) in
Figure 47 . This simple circuit is not very
accurate but it does provide the basic capability to disable the OVP function of
SNSOUT/PFCON. Note that lower voltages on SNSOUT/PFCON are blocked by the
diode so that the UVP is still functional.
Another possibility is to add a Zener diode function on SNSOUT/PFCON to limit the
voltage on this pin denoted by (2) in
Figure 47 .
Fig 46. Example of disabling the UVP function of SNSOUT/PFCON
001aal469
100
μ
A
1.5 V
SNSOUT/PFCON
SUPREG = 10.9 V
8.2 k
Ω
3.3 k
Ω
1N4148
V
aux
TEA1613
OVP
latched shutdown
3.5 V
COMP
UVP
protection timer
2.35 V
COMP