EL7512CY 데이터 시트보기 (PDF) - Elantec -> Intersil
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EL7512CY Datasheet PDF : 9 Pages
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EL7512C - Preliminary
High Frequency PWM Step-Up Regulator
The inductor has peak and average current decided by:
ILPK = ILAVG + ∆----2-I--L--
ILAVG = 1----I-–-O----D--
The inductor should be chosen to be able to handle this
current. Furthermore, due to the fixed internal compen-
sation, It is recommended that maximum inductance of
10µH and 15µH to be used in the 5V and 12V or higher
output voltage, respectively.
The output diode has average current of IO, and peak
current the same as the inductor's peak current. Schottky
diode is recommended and it should be able to handle
those currents.
Output voltage ripple is the product of peak inductor
current times the ESR of output capacitor. Low ESR
capacitor is to be used to reduce the output ripple. The
minimum out capacitance of 330µF, 47µF, and 33µF is
recommended for 5V, 12V, and 16V for 600kHz switch-
ing frequency, respectively. For 1MHz switching
frequency, 220µF, 33µF, and 22µF capacitor can be
used for the output voltages. In addition to the voltage
rating, the output capacitor should also be able to handle
the rms current is given by:
ICORMS =
(1
–
D)
×
D
+
I---L--∆-A---I-V-L---2-G---2-
×
1--1-2--
×
ILAVG
Layout Considerations
The layout is very important for the converter to func-
tion properly. Power Ground ( ) and Signal Ground (---)
should be separated to ensure that the high pulse current
in the Power Ground never interferes with the sensitive
signals connected to Signal Ground. They should only
be connected at one point.
The trace connected to pin 8 (FB) is the most sensitive
trace. It needs to be as short as possible and in a “quiet”
place, preferably between PGND or SGND traces.
In addition, the bypass capacitor connected to the VDD
pin needs to be as close to the pin as possible.
The heat of the chip is mainly dissipated through the
PGND pins. Maximizing the copper area around these
pins is preferable. In addition, a solid ground plane is
always helpful for the EMI performance.
The demo board is a good example of layout based on
these principles. Please refer to the EL7512C Applica-
tion Brief for the layout.
7
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