EL7640, EL7641, EL7642
V
CDLY
IN
V
REF
V
BOOST
t
ON
t
DEL1
V
OFF
t
DEL2
V
ON
START-UP SEQUENCE
TIMED BY C
DLY
FIGURE 23. START-UP SEQUENCE
The C
DEL
capacitor is typically 220nF and has a usable
range from 47nF minimum to several microfarads – only
limited by the leakage in the capacitor reaching µA levels.
Component Selection for Start-up Sequencing and
Fault Protection
The C
capacitor is typically set at 220nF and is required
to stabilize the V output. The range of C is from
REF
C
should be at least 1/5 of the value of C
(see
the fault time-out will be
DEL
above). Note with 220nF on C
REF
REF
REF
DEL
22nF to 1µF and should not be more than five times the
typically 50ms and the use of a larger/smaller value will vary
this time proportionally (e.g. 1µF will give a fault time-out
period of typically 230ms).
capacitor on C
to ensure correct start-up operation.
DEL
FN7415.1
16
September 26, 2005
INTERSIL [ Intersil ]
