ISL97642 Intersil Corporation, ISL97642 Datasheet - Page 16

• Manufacturer Part Number: ISL97642
• Description: TFT-LCD DC/DC
• Manufacturer: Intersil Corporation

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Component Selection for Start-up Sequencing and
Fault Protection
The C
to stabilize the V
22nF to 1µF and should not be more than five times the
capacitor on C
The C
from 22nF minimum to several microfarads – only limited by
the leakage in the capacitor reaching µA levels. C
be at least 1/5 of the value of C
NOTE: Not to scale
DEL
REF
capacitor is typically 100nF and has a usable range
capacitor is typically set at 220nF and is required
DEL
REF
V
ON SLICE
to ensure correct start-up operation.
output. The range of C
CIRCUIT
V
BOOST
V
16
CDEL
V
V
V
REF
OFF
REF
ON
IN
(see Figure 22). Note that
REF
FIGURE 22. START-UP SEQUENCE
is from
DEL
START-UP SEQUENCE
t
t
ON
DEL1
should
TIMED BY C
ISL97642
DEL
with 100nF on C
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).
Fault Sequencing
The ISL97642 has an advanced fault detection system,
which protects the IC from both adjacent pin shorts during
operation and shorts on the output supplies. A high quality
layout/design of the PCB (in respect of grounding quality and
decoupling) is necessary to avoid falsely triggering the fault
t
DEL3
t
DEL2
DEL
OPERATION
NORMAL
, the fault time-out will be typically 23ms
PRESENT
FAULT
June 18, 2007
FN6436.0