ADP3041 Ver la hoja de datos (PDF) - Analog Devices
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ADP3041 Datasheet PDF : 16 Pages
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ADP3041
COMP is allowed to rise slowly until the control loop limits the
voltage to that required for regulation. SS continues to rise and
no longer affects COMP once soft start is complete.
When SD goes low, an internal switch discharges the SS
capacitor to return its voltage to zero for soft restart.
Because of the large current that flows into the main MOSFET
switch, it is provided with a separate PGND return to the nega-
tive supply terminal to avoid corrupting the small-signal return,
GND, that can be used as a sense line at the output load point.
Buffers
This family of buffers is designed to drive large capacitive loads
in LCD applications. Each has high output current drive and
rail-to-rail input/output operation and can be powered from a
single 12 V supply. They are also intended for other applications
where low distortion and high output current drive are needed.
Input Overvoltage Protection
As with any semiconductor device, whenever the input exceeds
either supply voltage, attention needs to be paid to the input
overvoltage characteristics. As an overvoltage occurs, the ampli-
fier could be damaged, depending on the voltage level and the
magnitude of the fault current. When the input voltage exceeds
either supply by more than 0.6 V, the internal pin junctions
allow current to flow from the input to the supplies.
This input current is not inherently damaging to the device as
long as it is limited to 5 mA or less. If a condition exists using
the buffers where the input exceeds the supply more than 0.6 V,
a series external resistor should be added. The size of the resis-
tor can be calculated by using the maximum overvoltage divided
by 5 mA. This resistance should be placed in series with the
input exposed to an overvoltage.
Output Phase Reversal
The buffer family is immune to phase reversal. Although the
device’s output does not change phase, large currents due to
input overvoltage could damage the device. In applications
where the possibility of an input voltage exceeding the supply
voltage exists, overvoltage protection should be used as described
in the previous section.
APPLICATION INFORMATION
Output Voltage
The ADP3041 operates with an adjustable output from VIN to
12 V. The output voltage is fed back to the ADP3041 via resis-
tor dividers R1 and R2 (Figure 1). The feedback voltage is
1.233 V, so the output voltage is set by the formula
VOUT
= 1.233V
× 1 +
R1
R2
(1)
Because the feedback bias current is 100 nA maximum, R2 may
have a value up to 100 kΩ with minimum error due to the bias
current.
Inductor Selection
For most applications, the inductor used with the ADP3041
should be in the range of 1 µH to 22 µH. Several inductor
manufacturers are listed in Table I. When selecting an inductor,
it is important to make sure that the inductor used with the
ADP3041 is able to handle a peak current without saturation, and
that the peak current is below the current limit of the ADP3041.
Part
CMD4D11-4R7M
CCDRH5D18-100
CR43-4R7
CR43-100
DS1608-472
DS1608-103
D52LC-4R7M
D52LC-100M
L (µH)
4.7
10
4.7
10
4.7
10
Table I. Inductor Manufacturers
Max DCR (mΩ)
Height (mm)
166
1.1
124
2.0
109
3.5
182
3.5
60
2.9
75
2.9
4.7
84
2.0
10
137
2.0
Vendor
Sumida
847-545-6700
www.sumida.com
Coilcraft
847-639-6400
www.coilcraft.com
Toko
847-297-0070
www.tokoam.com
REV. D
–11–
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