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PDF AP65453 Data sheet ( Hoja de datos )
| Número de pieza | AP65453 | |
| Descripción | 650kHz ADAPTIVE COT STEP-DOWN CONVERTER | |
| Fabricantes | Diodes | |
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AP65453
4A, 18V, 650kHz ADAPTIVE COT STEP-DOWN CONVERTER
Description
The AP65453 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 TVs and monitors.
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 adaptive, constant on-time control supports seamless transition
between continuous conduction mode (CCM) at higher load
conditions and discontinuous conduction mode (DCM) at lighter load
conditions.
Pin Assignments
( Top View )
EN 1
FB 2
VREG5 3
SS 4
8 VIN
7 BS
6 SW
5 GND
SO-8EP
DCM allows AP65453 to maintain high efficiency at light load
conditions. The AP65453 also features programmable soft-start,
UVLO, OTP and OCP to protect the circuit.
This IC is available in SO-8EP package.
Features
Fixed Frequency Emulated Constant On-time Control
Good Stability Independent of the Output Capacitor ESR
Fast Load Transient Response
Synchronous Rectification: 90mΩ Internal High-side Switch
and 57mΩ 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.
AP65453
Document number: DS37999 Rev. 1 - 2
1 of 14
www.diodes.com
June 2015
© Diodes Incorporated
1 page  
Electrical Characteristics (@TA = +25°C, VIN = 12V, unless otherwise specified.)
AP65453
Parameter
SUPPLY VOLTAGE (VIN PIN)
Input Voltage
Quiescent Current
Shutdown Supply Current
UNDER VOLTAGE LOCKOUT
UVLO Threshold
UVLO Hysteresis
ENABLE (EN PIN)
EN High-level Input Voltage
EN Low-level Input Voltage
VOLTAGE REFERENCE (FB PIN)
Feedback Voltage
Feedback Bias Current
VREG5 OUTPUT
VREG5 Output Voltage
Source Current Capability
Load Regulation
Line Regulation
MOSFET
High-side Switch On-resistance
Low-side Switch On-resistance
CURRENT LIMIT
High Level Current Limit
ON-TIME TIMER
On-Time
Minimum Off-Time
THERMAL SHUTDOWN
Thermal Shutdown
Thermal Shutdown Hysteresis
SOFT START (SS PIN)
Soft-start Source Current
Soft-start Discharge Current
OVER VOLTAGE PROTECTION
OVP Trip Threshold
Symbol
VIN
IQ
ISHDN
VUVLO
VHYS
VENH
VENL
VFB
IFB
VVREG5
-
-
-
RDSONH
RDSONL
ILIM-H
Conditions
-
VFB=0.85V
VEN=0V
VIN Rising Test VREG5
Voltage
VIN Falling Test VREG5
Voltage
-
-
VOUT=1.05V
VFB=0.8V
6.0V<VIN<18V
0<IVREG5<5mA
VIN=6V, VVREG5=4V
0<IVREG5<5mA
6.0V<VIN<18V IVREG5=5mA
-
-
L=1.5μH
tON
tOFF-MIN
TOTSD
THYS
ISS-SOURCE
ISS-DISCHARGE
-
VIN=12V, VOUT=1.05V
VFB=0.7V
-
-
VSS=1.0V
VSS=0.5V
-
Min Typ Max
4.5 - 18
- 0.6 0.75
- 1 10
3.6 3.85 4.1
0.16 0.35 0.47
1.25 -
18
- - 0.85
0.753
-0.1
0.765
0
0.777
0.1
4.8 5.1 5.4
- 100 -
- - 100
- - 20
- 0.090 -
- 0.057 -
4.6 5.6 6.9
- 150 -
- 260 310
- 150 -
- 25 -
4.2 6.0 7.8
0.1 0.2
-
115 120 125
Unit
V
mA
μA
V
V
V
V
V
μA
V
mA
mV
mV
Ω
Ω
A
ns
ns
°C
°C
μA
mA
%
AP65453
Document number: DS37999 Rev. 1 - 2
3 of 14
www.diodes.com
June 2015
© Diodes Incorporated
5 Page 
Application Information (cont.)
AP65453
Figure 5 Feedback Divider Network
Output Voltage (V)
R1 (kΩ)
R2 (kΩ)
1 6.81 22.1
1.05
8.25 22.1
1.2 12.7 22.1
1.5 21.5 22.1
1.8 30.1 22.1
2.5 49.9 22.1
3.3 73.2 22.1
5 124 22.1
Table 1 Resistor Selection for Common Output
Voltages
Inductor
Calculating the inductor value is a critical factor in designing a buck converter. For most designs, the following equation can be used to calculate
the inductor value:
L
VOUT (VIN
VIN ΔIL
VOUT
fSW
)
Where ΔIL is the inductor ripple current and fSW is the buck converter switching frequency.
Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is calculated from:
IL(MAX)
ILOAD
ΔIL
2
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 3.3µH inductor with a DC current rating of at least 25% higher than the maximum load current is recommended for most applications.
For highest efficiency, the inductor’s DC resistance should be less than 100mΩ. Use a larger inductance for improved efficiency under light load
conditions.
The phase boost can be achieved by adding an additional feed forward capacitor (C7) in parallel with R1.
Output Voltage (V)
1
1.05
1.2
1.5
1.8
2.5
3.3
5
C7(pF)
5-22
5-22
5-22
5-22
L1(µH)
1.0-1.5
1.0-1.5
1.0-1.5
1.5
1.5
2.2
2.2
3.3
C8+C9(µF)
22-68
22-68
22-68
22-68
22-68
22-68
22-68
22-68
Input Capacitor
Table 2. Recommended Component Selection
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 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 ceramic capacitor greater than 10µF is sufficient.
AP65453
Document number: DS37999 Rev. 1 - 2
10 of 14
www.diodes.com
June 2015
© Diodes Incorporated
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet AP65453.PDF ] | |
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