VN1160/ VN1160-1/ VN1160T
FUNCTIONAL DESCRIPTION
1) Normal operation (see Fig.1)
When a nominal load (higher than a 20W bulb) is
connected to the OUT pin, the device oscillates by
charging the CEXT capacitor up to the threshold voltage
V
ch
quickly, and then slowly discharging CEXT to the
threshold voltage V
cl
by a constant current I
CEXT
.
The self oscillating frequency of the device is determined
by the relation :
Icext
fosc = -----------------------------------------------------------
2
×
C ext
× (
V ch – Vcl
)
The duty cycle is close to 50%.
2) Low load condition (see Fig.1)
If the load is lower than the load of a 14W bulb, the
device will detect the low load at the end of the ON
phase, and will double the oscillating frequency.
3) Overload and overtemperature shutdown (see
Fig.1)
In the case of a short circuit of the load, the output current
I
OUT
is limited to the I
LIM
value.
If the junction temperature becomes too hot (T
j
> T
jsh
),
the device turns off, and waits for the next cycle to turn on
providing that the junction temperature has cooled to
below T
jrs
.
5/10
1
ETC [ ETC ]
