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PDF AP65452 Data sheet ( Hoja de datos )
| Número de pieza | AP65452 | |
| Descripción | 650kHz ADAPTIVE COT STEP-DOWN CONVERTER | |
| Fabricantes | Diodes | |
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AP65452
4A, 18V, 650kHz ADAPTIVE COT STEP-DOWN CONVERTER
Description
The AP65452 is an adaptive constant on-time mode synchronous
buck converter providing high efficiency, excellent transient response
and high DC output accuracy for low-voltage regulation in digital TV
and monitor.
The constant-on-time control scheme handles wide input/output
voltage ratios and provides low external component count. The
internal proprietary circuit enables the device to adopt both low
equivalent series resistance (ESR) output capacitors, such as
SP-CAP or POSCAP and ultra-low ESR ceramic capacitors.
The AP65452 features programmable soft-start, UVLO, OTP and
OCP to protect the circuit.
This IC is available in SO-8EP package.
Pin Assignments
Features
Fixed Frequency Emulated Constant On-time Control
Good Stability Independent of the Output Capacitor ESR
Fast Load Transient Response
Synchronous Rectification: 65mΩ Internal High-side Switch and
36mΩ Internal Low-side Switch
Wide Input Voltage Range: 4.5V to 18V
Output Voltage Range: 0.76V to 6V
4A Continuous Output Current
650kHz Switching Frequency
Built-in Over Current Limit
Built-in Thermal Shutdown Protection
Programmable Soft-start
Pre-biased Start-up
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Applications
Gaming Consoles
Flat Screen TV Sets and Monitors
Set-Top Boxes
Distributed Power Systems
Home Audio
Consumer Electronics
Network Systems
FPGA, DSP and ASIC Supplies
Green Electronics
Notes:
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
Typical Applications Circuit
INPUT
VIN
12V
C1
20μF
OFF
C4
8.2nF
8
IN
ON 1
EN
4
SS
7
BST
6
SW
AP65452
2
FB
3
5 VREG5
GND
C5 L1
0.1µF 1.5μH
R1
8.25kΩ
R2
22.1kΩ
C3
1µF
OUTPUT
VOUT
1.05V
C2
44μF
Figure 1 Typical Application Circuit
AP65452
Document number: DS37305 Rev. 2 - 2
1 of 13
www.diodes.com
November 2014
© Diodes Incorporated
1 page  
AP65452
Typical Performance Characteristics (@TA = +25°C, VIN = 12V, VOUT = 1.05V, unless otherwise specified.)
85˚C
25˚C
-40˚C
-40˚C
25˚C
85˚C
VIN=18V
VIN=12V
VIN=4.5V
AP65452
Document number: DS37305 Rev. 2 - 2
5 of 13
www.diodes.com
IO=0A
IO=1A
November 2014
© Diodes Incorporated
5 Page 
AP65452
Application Information (cont.)
Output Capacitor (cont.)
Maximum capacitance required can be calculated from the following equation:
ESR of the output capacitor dominates the output voltage ripple. The amount of ripple can be calculated from the equation below:
Voutcapacitor ∆Iinductor * ESR
An output capacitor with ample capacitance and low ESR is the best option. For most applications, a 22µF to 68µF ceramic capacitor will be
sufficient.
Co
L(Iout
∆Iinductor )2
2
(∆ V Vout)2 Vout2
Where ∆V is the maximum output voltage overshoot.
Bootstrap Capacitor
To ensure the proper operation, a ceramic capacitor must be connected between the VBST and SW pin. A 0.1µF ceramic capacitor is sufficient.
VREG5 Capacitor
To ensure the proper operation, a ceramic capacitor must be connected between the VREG5 and GND pin. A 1µF ceramic capacitor is sufficient.
PC Board Layout
1. The AP65452 works at 4A load current, heat dissipation is a major concern in layout the PCB. A 2oz Copper in both top and bottom
layer is recommended.
2. Provide sufficient vias in the thermal exposed pad for heat dissipate to the bottom layer.
3. Provide sufficient vias in the Output capacitor GND side to dissipate heat to the bottom layer.
4. Make the bottom layer under the device as GND layer for heat dissipation. The GND layer should be as large as possible to provide
better thermal effect.
5. Make the Vin capacitors as close to the device as possible.
6. Make the VREG5 capacitor as close to the device as possible.
7. The thermal pad of the device should be soldered directly to the PCB exposed copper plane to work as a heatsink. The thermal vias in
the exposed copper plane increase the heat transfer to the bottom layer.
Figure 6 PC Board Layout
AP65452
Document number: DS37305 Rev. 2 - 2
11 of 13
www.diodes.com
November 2014
© Diodes Incorporated
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet AP65452.PDF ] | |
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