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PDF AP6508 Data sheet ( Hoja de datos )
| Número de pieza | AP6508 | |
| Descripción | 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER | |
| Fabricantes | Diodes | |
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AP6508
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER
Description
Pin Assignments
The AP6508 is a 500kHz switching frequency internal
compensated synchronous DCDC buck converter. It has
integrated compensation, and low RDSON high and low side
MOSFETs.
The AP6508 enables continues load current of up to 3A with
efficiency as high as 93%.
The AP6508 features current mode control operation, which
enables fast transient response times and easy loop
stabilization.
The AP6508 has external programmable softstart and a
Power Good indicator enabling sequencing and ramp control.
The AP6508 simplifies board layout and reduces space
requirements with its high level of integration and minimal
need for external components, making it ideal for distributed
power architectures.
The AP6508 is available in a standard Green DFN4030-14
package with exposed PAD for improved thermal
performance and is RoHS compliant.
(Top View)
IN 1
SW
SW
2
3
SW 4
SW 5
BST 6
EN 7
Exposed Pad
14 AGND
13 GND
12 GND
11 VCC
10 SS
9 PG
8 FB
DFN4030-14
Features
Applications
• VIN 4.5V to 21V
• VOUT adjustable to 0.8V
• 500kHz switching frequency
• Enable pin
• External Softstart
• Power Good
• Protection
o OCP
o Thermal Shutdown
• Lead Free Finish/ RoHS Compliant (Note 1)
• Gaming Consoles
•
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•
TV sets and Monitors
Set Top Boxes
• Distributed power systems
• Home Audio
• Consumer electronics
Note: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at
http://www.diodes.com/products/lead_free.html.
Typical Application Circuit
100
VOUT = 2.5V
90
80
70
60
50
VIN = 12V
VIN = 5V
40
0 12 3
LOAD CURRENT (A)
Efficiency vs. Load Current
AP6508
Document number: DS33437 Rev. 4 - 2
1 of 14
www.diodes.com
Typical Application Circuit
July 2011
© Diodes Incorporated
datasheet pdf - http://www.DataSheet4U.net/
1 page  
AP6508
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER
Typical Performance Characteristics
1.3
16
14
1.25
12
1.2
10
1.15 8
6
1.1
4
1.05
2
1
0 5 10 15 20 25
INPUT VOLTAGE
Quiescent Supply Current vs. Input Voltage
5.05
5.045
0
0 5 10 15 20 25
INPUT VOLTAGE (V)
Shutdown Supply vs. Input Voltage
7
6.8
VIN = 12V
VOUT = 1.2V
6.6
5.04
5.035
5.03
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6.4
6.2
6
5.8
5.6
5.025
5.02
0
1.225
5 10 15 20
INPUT VOLTAGE (V)
VCC Regulator Line Regulation
25
5.4
5.2
5
-20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
Current Limit vs. Temperature
1.21
1.2245
1.224
1.2235
1.223
1.2225
1.222
1.2215
1.221
1.208
1.206
1.204
1.202
1.2
1.198
1.196
VIN = 12V
VIN = 5V
1.2205
1.22
0
5 10 15 20 25
INPUT VOLTAGE (V)
Line Regulation vs. Output Current
1.194
1.192
0
AP6508
Document number: DS33437 Rev. 4 - 2
5 of 14
www.diodes.com
0.5 1 1.5 2 2.5
OUTPUT CURRENT (A)
Load Regulation vs. Output Current
3
July 2011
© Diodes Incorporated
datasheet pdf - http://www.DataSheet4U.net/
5 Page 
AP6508
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER
Application Information (cont.)
Inductor (cont.)
Peak current determines the required saturation current
rating, which influences the size of the inductor.
Saturating the inductor decreases the converter
efficiency while increasing the temperatures of the
inductor and the internal MOSFETs. Hence choosing an
inductor with appropriate saturation current rating is
important.
A 1µH to 10µH inductor with a DC current rating of at
least 25% percent higher than the maximum load current
is recommended for most applications.
For highest efficiency, the inductor’s DC resistance
should be less than 200mΩ. Use a larger inductance for
improved efficiency under light load conditions.
Input Capacitor
The input capacitor reduces the surge current drawn from
the input supply and the switching noise from the device.
The input capacitor has to sustain the ripple current
produced during the on time on the upper MOSFET. It
must hence have a low ESR to minimize the losses.
The RMS current rating of the input capacitor is a critical
parameter that must be higher than the RMS input
current. As a rule of thumb, select an input capacitor
which has an RMS rating that is greater than half of the
maximum load current.
Due to large dI/dt through the input capacitors,
electrolytic or ceramics should be used. If a tantalum
must be used, it must be surge protected. Otherwise,
capacitor failure could occur. For most applications, a
4.7µF ceramic capacitor is sufficient.
Output Capacitor
The output capacitor keeps the output voltage ripple
small, ensures feedback loop stability and reduces the
overshoot of the output voltage. The output capacitor is a
basic component for the fast response of the power
supply. In fact, during load transient, for the first few
microseconds it supplies the current to the load. The
converter recognizes the load transient and sets the duty
cycle to maximum, but the current slope is limited by the
inductor value.
Maximum capacitance required can be calculated from
the following equation:
Co
=
L(Iout
+
ΔIinductor
2
)2
(Δ V + Vout )2 − Vout 2
Where ΔV is the maximum output voltage overshoot.
ESR of the output capacitor dominates the output voltage
ripple. The amount of ripple can be calculated from the
equation below:
Voutcapacitor = ΔIinductor * ESR
An output capacitor with ample capacitance and low ESR
is the best option. For most applications, a 22µF ceramic
capacitor will be sufficient.
PC Board Layout
This is a high switching frequency converter. Hence
attention must be paid to the switching currents
interference in the layout. Switching current from one
power device to another can generate voltage transients
across the impedances of the interconnecting bond wires
and circuit traces. These interconnecting impedances
should be minimized by using wide, short printed circuit
traces.
34mm
External feedback
resistor dividers
must be placed
close to the FB pin
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52mm
Input capacitor C1
must be placed as
close as possible to the
IC and to L1.
AP6508 is exposed at the bottom of the package and must
be soldered directly to a well designed thermal pad on the
PCB. This will help to increase the power dissipation.
External Bootstrap Diode
It is recommended that an external bootstrap diode be
added when the input voltage is no greater than 5V or the
5V rail is available in the system. This helps to improve
the efficiency of the regulator. This solution is also
applicable for D > 65%. The bootstrap diode can be a low
cost one such as BAT54 or a schottky that has a low Vf.
5V
BST 6
BOOST
DIODE
AP6508
10nF
SW 2,3,4,5
Figure 3. External Bootstrap Diode
AP6508
Document number: DS33437 Rev. 4 - 2
11 of 14
www.diodes.com
July 2011
© Diodes Incorporated
datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet AP6508.PDF ] | |
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