FAN7532 Просмотр технического описания (PDF) - Fairchild Semiconductor
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FAN7532 Datasheet PDF : 16 Pages
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2) Open Lamp Protection (OLP) Mode
After the lamp has successfully ignited, the FAN7532
enters run mode. In this mode, if one of the cathodes
isn’t correctly connected to the ballast, the ballast stops
operation for safety until the lamp is changed and a new
one is connected between the lamp and the ballast. As
soon as the voltage of OLP pin exceeds 2V, the IC
15.6V
VUVLO+
VUVLO-
enters the protection mode. However, the FAN7532 out-
puts are only disabled in this mode. To exit protection
mode, the lamp must be replaced or correctly connected
to the ballast.
VCPH
5V
2.9V
FREQ
fPH
fOSC
Reset when open lamp
Reset when open lamp
OLP
VLAMP
Open lamp
Only gate driver
is disabled
Open lamp
Only gate driver
is disabled
Run
Open
Lamp
Preheating
Ignition
Run
Open
Lamp
Preheating
Run
Ignition FAN7532 Rev. 00
Figure 19. Timing Diagram (OLP Mode)
8. PCB Layout Guides
Component selection and placement on the PCB is very
important when using power control ICs. Bypass the VCC
to GND as close to the IC terminals as possible with a
low ESR/ESL capacitor, as shown in Figure 20. This
bypassed capacitor can reduce the noise from the power
supply parts, such as a startup resistor and a charge
pump. The GND lead should be directly connected to the
low-side power MOSFET using an individual PCB trace.
In addition, the ground return path of the timing compo-
nents (CPH, CT, RPH, RT) and VCC decoupling capaci-
tor should be connected directly to the IC GND lead and
not via separate traces or jumpers to other ground traces
on the board. These connection techniques prevent
high-current ground loops from interfering with sensitive
timing component operations and allow the entire control
circuit to reduce common-mode noise due to output
switching.
Figure 20. PCB Layout
© 2006 Fairchild Semiconductor Corporation
FAN7532 Rev. 1.0.2
12
www.fairchildsemi.com
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