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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: 65mInternal High-side Switch and
36mInternal 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
8.25k
R2
22.1kΩ
C3
1µF
OUTPUT
VOUT
1.05V
C2
44μF
Figure 1 Typical Application Circuit
AP65452
Document number: DS37305 Rev. 2 - 2
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AP65452
Pin Descriptions
Pin
Name
EN
Pin Number
SO-8EP
Function
1
Enable input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low
to turn off. Pull up with 100kresistor for automatic startup.
FB
2
Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage divider connected to
it from the output voltage.
VREG5
3
Internal power supply output pin to connect an additional capacitor. Connect a 1μF (typical) capacitor as close as
possible to the VREG5 and GND. This pin is not active when EN is low.
SS
GND
4
Soft-start control input pin. SS controls the soft start period. Connect a capacitor from SS to GND to set the soft-start
period.
5 Ground pin is the main power ground for the switching circuit.
SW
6
Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter
from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch.
BS
7
Bootstrap pin. A bootstrap capacitor is connected between the BS pin and SW pin. The voltage across the bootstrap
capacitor drives the internal high-side NMOS switch. A 0.1μF (typical) capacitor is required for proper operation.
VIN
8
Supply input pin. A capacitor should be connected between the VIN pin and GND pin to keep the DC input voltage
constant.
EP Connect the exposed thermal pad to GND on the PCB.
Functional Block Diagram
AP65452
Document number: DS37305 Rev. 2 - 2
Figure 2 Functional Block Diagram
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AP65452
Absolute Maximum Ratings (Note 4) (@TA = +25°C, unless otherwise specified.)
Symbol
Parameter
VIN Supply Voltage
VREG5
VREG5 Pin Voltage
VSW Switch Node Voltage
VBS Bootstrap Voltage
VFB Feedback Voltage
VEN Enable/UVLO Voltage
VSS Soft-sStart PIN
VGND
GND Pin Voltage
TST Storage Temperature
TJ Junction Temperature
TL Lead Temperature
ESD Susceptibility (Note 5)
HBM
Human Body Model
MM Machine Model
Rating
-0.3 to 20
-0.3V to +6.0
-1.0 to VIN +0.3
-0.3 to VSW +6.0
-0.3V to +6.0
-0.3V to +6.0
-0.3V to +6.0
-0.3 to 0.3
-65 to +150
+160
+260
2
200
Unit
V
V
V
V
V
V
V
V
°C
°C
°C
kV
V
Notes:
4. Stresses greater than the 'Absolute Maximum Ratings' specified above may cause permanent damage to the device. These are stress ratings only;
functional operation of the device at these or any other conditions exceeding those indicated in this specification is not implied. Device reliability may
be affected by exposure to absolute maximum rating conditions for extended periods of time.
5. Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when
handling and transporting these devices.
Thermal Resistance (Note 6)
Note:
Symbol
θJA
θJC
Parameter
Junction to Ambient
Junction to Case
SO-8EP
SO-8EP
Rating
70
30
6. Test condition: SO-8: Device mounted on 1"x1" FR-4 substrate PCB, 2oz copper, with minimum recommended pad layout.
Unit
°C/W
°C/W
Recommended Operating Conditions (Note 7) (@TA = +25°C, unless otherwise specified.)
Note:
Symbol
VIN
TJ
TA
Parameter
Supply Voltage
Operating Junction Temperature Range
Operating Ambient Temperature Range
Min
4.5
-40
-40
7. The device function is not guaranteed outside of the recommended operating conditions.
Max
18.0
+125
+85
Unit
V
°C
°C
AP65452
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AP65452
Electrical Characteristics (@TA = +25°C, VIN = 12V, unless otherwise specified.)
Parameter
SUPPLY VOLTAGE (VIN PIN)
Input Voltage
Quiescent Current
Shutdown Supply Current
UNDER VOLTAGE LOCKOUT
UVLO Threshold
Symbol
VIN
IQ
ISHDN
VUVLO
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
VHYS
VENH
VENL
VFB
IFB
VREG5 Output Voltage
Source Current Capability
Load Regulation
Line Regulation
VVREG5
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
RDSONH
RDSONL
ILIM-H
tON
tOFF-MIN
TOTSD
THYS
ISS-SOURCE
ISS-DISCHARGE
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
VIN=12V, VOUT=1.05V
VFB=0.7V
VSS=1.2V
VSS=0.5V
Min
4.5
3.45
0.19
1.9
0.753
-0.1
4.7
4.6
4.2
0.1
Typ
0.9
3.6
3.75
0.32
0.765
0
5.1
110
0.075
0.036
5.3
150
260
160
30
6.0
0.2
Max
18
10
4.05
0.45
0.6
0.777
0.1
5.5
60
20
6.8
310
7.8
Unit
V
mA
μA
V
V
V
V
V
μA
V
mA
mV
mV
A
ns
ns
ºC
ºC
μA
mA
AP65452
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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
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IO=1A
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