ISL78010_11 INTERSIL [Intersil Corporation], ISL78010_11 Datasheet - Page 17

• Manufacturer Part Number: ISL78010_11
• Description: Automotive Grade TFT-LCD Power Supply
• Manufacturer: INTERSIL [Intersil Corporation]

If V
prevent damage to the chip. While in current limit, the part
acts like a current source, and the regulated output will drop.
If the output drops below the fault threshold, a ramp will be
initiated on C
chip will be disabled upon completion of the ramp.
In some circumstances (depending on ambient temperature
and thermal design of the board), continuous operation at
current limit may result in the over-temperature threshold
being exceeded, which will cause the part to disable
immediately.
All I/O also has ESD protection, which in many cases will
also provide overvoltage protection relative to either ground
or VDD. However, these will not generally operate unless
absolute maximum ratings are exceeded.
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
range from 47nF minimum to several microfarads. It is
limited only by leakage in the capacitor reaching µA levels.
C
with 220nF on C
and the use of a larger or smaller value will vary this time
proportionally (e.g., 1µF will give a fault time-out period of
typically 230ms).
Fault Sequencing
The ISL78010 has advanced fault detection systems which
protect the IC from both adjacent pin shorts during operation
and shorts on the output supplies.
A high-quality layout and design of the PCB with respect to
grounding and decoupling is necessary to avoid falsely
triggering the fault detection scheme, especially during
start-up. See “Layout Recommendation” on page 17 and
“Component Selection for Start-Up Sequencing and Fault
DEL
BOOST
REF
DEL
should be at least 1/5 of the value of C
capacitor is typically 220nF and has a usable
capacitor is typically set at 220nF and is required
is excessively loaded, the current limit will
DELAY
DEL
DEL
REF
to ensure correct start-up operation.
and, provided the fault is sustained, the
the fault time-out will typically be 50ms,
output. The range of C
17
REF
REF
is from
. Note that
ISL78010
Protection” on page 17 to avoid problems during initial
evaluation and prototype PCB generation.
Over-Temperature Protection
An internal temperature sensor continuously monitors the
die temperature. If the die temperature exceeds the thermal
trip point of +140°C, the device will shut down.
Layout Recommendation
Device performance, including efficiency, output noise,
transient response and control loop stability, is dramatically
affected by the PCB layout. PCB layout is critical, especially
at high switching frequency.
Some general guidelines for layout include:
An evaluation board, ISL78010EVAL1Z, is available to
illustrate the proper layout implementation. See “Ordering
Information” on page 1.
1. Place the external power components (the input
2. Place V
3. Minimize the length of traces carrying fast signals and
4. All feedback networks should sense the output voltage
5. The power ground (PGND) and signal ground (SGND)
6. A signal ground plane, separate from the power ground
7. Minimize feedback input track lengths to avoid switching
8. Connect all "NC" pins to the ground plane to improve
capacitors, output capacitors, boost inductor and output
diodes, etc.) in close proximity to the device. Traces to
these components should be kept as short and wide as
possible to minimize parasitic inductance and resistance.
high current.
directly from the point of load, and be as far away from LX
node as possible.
pins should be connected at only one point near the main
decoupling capacitors.
plane, should be used for ground return connections for
feedback resistor networks (R
capacitor, C
integrator capacitor, C
noise pickup.
thermal performance and switching noise immunity
between pins.
REF
22
and V
; the C
DD
DELAY
bypass capacitors close to the pins.
23
.
capacitor, C
1
, R
11
, R
41
7
) and the V
; and the
May 3, 2011
FN6501.1
REF