AN10907
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© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1 — 28 December 2010
65 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
is passed when the upper switching level of 4 V has been reached. At that moment, the
appropriate protective action is executed, the current source is stopped and RCPROT is
discharged by the external resistor.
In the case that the error condition ends before 4 V has been reached, the current source
is stopped and the pin discharges through the external resistor and no further action is
taken.
If the error condition is permanent, the system fluctuates between stopping
(RCPROT = 4 V) and restarting (RCPROT = 0.5 V). This is sometimes referred to as a
hiccup mode.
The protection timer is activated by one of the following:
•
overcurrent regulation SNSCURHBC
•
high frequency protection RFMAX
•
open loop protection SNSFB
•
undervoltage protection SNSOUT/PFCON
Protection can be forcibly activated (including restart) by increasing the RCPROT voltage
to above 4 V (but not higher than +12 V) using an external circuit.
10.4.2 RCPROT working as a restart timer
During certain error conditions, it may be desirable to temporarily disable the IC. This is
especially useful when an error can over-heat components. A temporary disable allows
power supply components to cool down, after which the IC must automatically restart. The
time to restart is determined by the restart timer.
Normally, the capacitor is discharged to 0 V. When an error occurs, C
prot
is charged and it
operates as a protection timer until it reaches the upper switching level of 4 V. After this,
the RCPROT pin becomes high ohmic and the external resistor discharges the external
capacitor. The restart time is exceeded when the lower switching level of 0.5 V is reached.
At that moment, the IC is restarted and the RCPROT pin is further discharged.
Fig 51. RCPROT operating as a restart timer
passed
0 V
0.5 V
no
yes
long
error
4 V
error
001aal064
V
RCPROT
t
restart time
