Diodes AP65550 User Manual
AP65550
Document number: DS36336 Rev. 2 - 2
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www.diodes.com
April 2014
© Diodes Incorporated
AP65550
Description
The AP65550 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 SPCAP or POSCAP and ultra-low ESR ceramic capacitors.
The adaptive on-time control supports seamless transition between
continuous conduction mode (CCM) at higher load conditions and
discontinuous conduction mode (DCM) at lighter load conditions.
DCM allows AP65550 maintain high efficiency at light load conditions.
The AP65550 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: 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
5A 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)
Pin Assignments
SW
VREG5
SS
EN
BS
GND
VIN
( Top View )
1
2
3
4
8
7
6
5
FB
SO-8EP
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
AP65550
L1
1.5μH
R1
8.25kΩ
R2
22.1kΩ
C5
0.1µF
C2
44μF
C1
20μF
C4
8.2nF
ON
OFF
8
IN
4
SS
1
EN
3
VREG5
6
SW
7
BST
2
FB
C3
1µF
5
GND
INPUT
OUTPUT
V
OUT
1.05V
VIN
12V
Figure 1. Typical Application Circuit
5A, 18V, 650kHz ADAPTIVE COT STEP-DOWN CONVERTER
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
AP65550
Document number: DS36336 Rev. 2 - 2
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April 2014
© Diodes Incorporated
AP65550
Pin
Name
Pin Number
Function
SO-8EP
EN
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 100kΩ resistor 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
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.
GND
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
Pin Descriptions
Functional Block Diagram
Figure 2. Functional Block Diagram
AP65550
Document number: DS36336 Rev. 2 - 2
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April 2014
© Diodes Incorporated
AP65550
Symbol
Parameter
Rating
Unit
VIN
Supply Voltage
-0.3 to 20
V
V
REG5
VREG5 Pin Voltage
-0.3V to +6.0
V
VSW
Switch Node Voltage
-1.0 to V
IN
+0.3
V
VBS
Bootstrap Voltage
-0.3 to VSW +6.0
V
VFB
Feedback Voltage
-0.3V to +6.0
V
VEN
Enable/UVLO Voltage
-0.3V to +6.0
V
VSS
SoftStart PIN
-0.3V to +6.0
V
V
GND
GND Pin Voltage
-0.3 to 0.3
V
TST
Storage Temperature
-65 to +150
°C
TJ
Junction Temperature
+160
°C
TL
Lead Temperature
+260
°C
ESD Susceptibility (Note 5)
HBM
Human Body Model
2
kV
MM
Machine Model
200
V
Symbol
Parameter
Rating
Unit
θ
JA
Junction to Ambient
SO-8EP
70
°C/W
θ
JC
Junction to Case
SO-8EP
30
°C/W
Symbol
Parameter
Min
Max
Unit
VIN
Supply Voltage
4.5
18.0
V
TJ
Operating Junction Temperature Range
-40
+125
°C
TA
Operating Ambient Temperature Range
-40
+85
°C
Absolute Maximum Ratings (Note 4) (@T
= +25°C, unless otherwise specified.)
A
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: 6. Test condition: SO-8: Device mounted on 1"x1" FR-4 substrate PCB, 2oz copper, with minimum recommended pad layout.
Recommended Operating Conditions (Note 7) (@T
Note: 7. The device function is not guaranteed outside of the recommended operating conditions.
= +25°C, unless otherwise specified.)
A
AP65550
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AP65550
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
SUPPLY VOLTAGE (VIN PIN)
Input Voltage
V
IN
—
4.5 — 18
V
Quiescent Current
IQ
VFB=0.85V
—
0.9 — mA
Shutdown Supply Current
I
SHDN
VEN=0V
—
3.6
10
μA
UNDER VOLTAGE LOCKOUT
UVLO Threshold
V
UVLO
VIN Rising Test VREG5
Voltage
3.45
3.75
4.05
V
UVLO Hysteresis
V
HYS
VIN Falling Test VREG5
Voltage
0.19
0.32
0.45
V
ENABLE (EN PIN)
EN High-level Input Voltage
V
ENH
—
1.9 — —
V
EN Low-level Input Voltage
V
ENL
— — —
0.6
V
VOLTAGE REFERENCE (FB PIN)
Feedback Voltage
VFB
V
OUT
=1.05V
0.753
0.765
0.777
V
Feedback Bias Current
IFB
VFB=0.8V
-0.1
0
0.1
μA
VREG5 OUTPUT
VREG5 Output Voltage
V
VREG5
6.0V<VIN<18V 0<I
VREG5
<5mA
4.7
5.1
5.5
V
Source Current Capability
—
VIN=6V, V
VREG5
=4V
—
110 — mA
Load Regulation
—
0<I
VREG5
<5mA
— — 60
mV
Line Regulation
—
6.0V<VIN<18V I
VREG5
=5mA
—
—
20
mV
MOSFET
High-side Switch On-resistance
R
DSONH
—
—
0.065 — Ω
Low-side Switch On-resistance
R
DSONL
—
—
0.036 — Ω
CURRENT LIMIT
High Level Current Limit
I
LIM-H
L=1.5μH
5.6
6.4
7.9
A
ON-TIME TIMER
On Time
tON
VIN=12V, VOUT=1.05V
—
150 — ns
Minimum Off Time
t
OFF-MIN
VFB=0.7V
—
260
310
ns
THERMAL SHUTDOWN
Thermal Shutdown
T
OTSD
— — +160 — °C
Thermal Shutdown Hysteresis
T
HYS
— — +30 — °C
SOFT START (SS PIN)
Soft-start Source Current
I
SS-SOURCE
VSS=1V
4.2
6.0
7.8
μA
Soft-start Discharge Current
I
SS-DISCHARGE
VSS=0.5V
0.1
0.2 — mA
Electrical Characteristics (@T
= +25°C, VIN = 12V, unless otherwise specified.)
A
AP65550
Document number: DS36336 Rev. 2 - 2
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April 2014
© Diodes Incorporated
AP65550
85˚C
-40˚C
25˚C
85˚C
25˚C
-40˚C
85˚C
25˚C
-40˚C
IO=5A
IO=2A
IO=3A
IO=4A
Typical Performance Characteristics (@T
= +25°C, VIN = 12V, V
A
= 3.3V, unless otherwise specified.)
OUT
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