Diodes AP1534SG-13 Pwm control 2a step-down converter Datasheet

AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
General Description
Features
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Input voltage: 3.6V to 18V
Output voltage: 0.8V to VCC.
Duty ratio: 0% to 99% PWM control
Oscillation frequency: 300KHz typical
Current limit, Enable function
Thermal Shutdown function
Built-in internal SW P-channel MOS
SOP-8L: Available in “Green” Molding Compound
(No Br, Sb)
Lead Free Finish/RoHS Compliant (Note 1)
AP1534 consists of step-down switching regulator with PWM
control. These devices include a reference voltage source,
oscillation circuit, error amplifier, internal PMOS.
AP1534 provides low-ripple power, high efficiency, and excellent
transient characteristics. The PWM control circuit is able to vary
the duty ratio linearly from 0 up to 99%. This converter also
contains an error amplifier circuit as well as a soft-start circuit that
prevents overshoot at startup. An enable function, an over
current protect function and a short circuit protect function are built
inside, and when OCP or SCP happens, the operation frequency
will be reduced from 300KHz to 50KHz. Also, an internal
compensation block is built in to minimize external component
count.
With the addition of an internal P-channel Power MOS, a coil,
capacitors, and a diode connected externally, these ICs can
function as step-down switching regulators. They serve as ideal
power supply units for portable devices when coupled with the
SOP-8L mini-packages, providing such outstanding features as
low current consumption. Since this converter can accommodate
an input voltage up to 18V, it is also suitable for the operation via
an AC adapter.
Applications
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PC Motherboard
LCD Monitor
Graphic Card
DVD-Video Player
Telecom Equipment
ADSL Modem
Printer and other Peripheral Equipment
Microprocessor Core Supply
Ordering Information
AP 1534 S G - 13
Device
AP1534SG-13
Notes:
Package
Green
Packing
S : SOP-8L
G : Green
13 : Tape & Reel
Package
Code
S
Packaging
(Note 2)
SOP-8L
13” Tape and Reel
Part Number Suffix
Quantity
2500/Tape & Reel
-13
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.
2. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at
http://www.diodes.com/datasheets/ap02001.pdf.
AP1534 Rev. 5
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Pin Assignments
( Top View )
FB 1
8
Vss
EN 2
7
Vss
OCSET 3
6
Output
VCC 4
5
Output
AP1534
SOP-8L
Pin Descriptions
Pin Name
Pin No.
FB
1
Feedback pin
EN
2
Power-off pin
H: Normal operation
(Step-down operation)
L: Step-down operation stopped
(All circuits deactivated)
OCSET
3
Add an external resistor to set max output current
VCC
4
IC power supply pin
Output
5, 6
Switch Pin. Connect external inductor/diode here. Minimize trace area at this
pin to reduce EMI
VSS
7, 8
GND Pin
AP1534 Rev. 5
Description
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Block Diagram
Output
Oscillation
Circuit
Reference Voltage
Source
Vcc
+
PWM-Switched
Control Circuit
FB
-
Thermal
Shutdown
VEN
EN
100uA
Vss
OCSET
Absolute Maximum Ratings
Symbol
Parameter
ESD HBM Human Body Model ESD Protection
ESD MM
Machine Model ESD Protection
Rating
Unit
4.5
150
KV
V
VCC
VCC Pin Voltage
VSS - 0.3 to VSS + 20
V
VFB
Feedback Pin Voltage
VSS - 0.3 to VCC
V
VEN
EN Pin Voltage
VSS - 0.3 to VIN
V
VOUT
Switch Pin Voltage
VSS - 0.3 to VIN
V
PD
Power Dissipation
Internally limited
mW
TJ
Operating Junction Temperature Range
TST
Storage Temperature Range
-40 to +125
o
C
-65 to +150
o
C
Caution: The absolute maximum ratings are rated values exceeding which the product could suffer physical damage.
These values must therefore not be exceeded under any conditions.
Recommended Operating Conditions
Symbol
VIN
IOUT
TA
AP1534 Rev. 5
Parameter
Input Voltage
Output Current
Operating Ambient Temperature
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Min
3.6
0
-20
Max
18
2
85
Unit
V
A
o
C
FEBRUARY 2009
© Diodes Incorporated
AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Electrical Characteristics
(VIN = 12V, TA = 25°C, unless otherwise specified)
Symbol
Parameter
Conditions
VFB
Feedback Voltage
IOUT = 0.1A
IFB
Feedback Bias Current
IOUT = 0.1A
ISW
Switch Current
-Current Consumption During
ISHDN
VEN = 0V
Power Off
∆VOUT
Line Regulation
VIN = 5V~18V
/ VIN
∆VOUT
Load Regulation
IOUT = 0.1 to 2A
/VOUT
fOSC Oscillation Frequency
Measure waveform at SW pin
Frequency of Current Limit
fOSC1
Measure waveform at SW pin
or Short Circuit Protect
VIH
Evaluate oscillation at SW pin
EN Pin Input Voltage
VIL
Evaluate oscillation stop at SW pin
ISH
-EN Pin Input Leakage
Current
ISL
-IOCSET OCSET Pin Bias Current
-VIN = 5V, VFB = 0V
RDS(ON) Internal MOSFET RDS(ON)
VIN = 12V, VFB = 0V
VIN = 12V, VOUT = 5V
EFFI Efficiency
IOUT = 2A
TSHDN Thermal shutdown threshold
Thermal shutdown
THYS
hysteresis
Thermal Resistance
θJA
SOP-8L (Note 3)
Junction-to-Ambient
Thermal Resistance
θJC
SOP-8L (Note 3)
Junction-to-Case
Notes:
Min
0.784
2.0
Typ.
0.8
0.1
-
Max
0.816
0.5
-
Unit
V
µA
A
-
10
-
µA
-
1
2
%
-
0.2
0.5
%
240
300
400
KHz
-
50
-
KHz
2.0
75
-
20
-10
90
160
100
0.8
105
-
-
91
-
%
-
150
-
°C
-
55
-
°C
-
127
-
o
C/W
-
28
-
o
C/W
V
µA
µA
µA
mΩ
3. Test condition for SOP-8L: Device mounted on FR-4 substrate PC board, 2oz copper, with minimum recommended pad layout.
For better thermal performance, larger copper pad for heatsink is needed.
Typical Application Circuit
22uH
L1
Vcc
V IN
R OCSET COCSET
5.6K
Option
CIN
CC
Optional
AP1534
CVcc
0.1uF
REN
100K
EN
RA
6.8K
+
FB
OCSET
470uF
VOUT =5V/2A
Output
VSS
D1
B240A
(Note 4)
-
+
C
0.1uF
-
COUT
470uF
RB
1.3K
CEN
0.1uF
Note: VOUT = VFB x (1+RA /RB )
RB =0.7K~5K ohm
Notes:
4. Suggested DIODES Power Schottky P/N: B240/B340 series.
AP1534 Rev. 5
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Typical Performance Characteristics
VIN vs VFB
(VOUT=3.3V, IOUT=0.2A)
0.820
0.815
0.810
0.805
0.800
0.795
0.790
0.785
0.780
V FB (V)
F OSC (kHz)
326
324
322
320
318
316
314
312
310
308
306
VIN vs Frequency
(VOUT=3.3V, IOUT=0.2A)
0
2
4
8
10
VIN (V)
12
14
16
0
18
6
8
10
VIN (V)
Load Regulation
(VIN=5V, VOUT=3.3V)
1.0%
0.0%
-1.0%
-2.0%
-3.0%
2
4
Line Regulation
2.0%
0
2
(VOUT=3.3V, IOUT=0.2A)
V OUT CHANGE (%)
V O UT C HANGE (%)
3.0%
6
4
6
8
10
VIN (V)
12
14
16
18
1.0%
0.8%
0.6%
0.4%
0.2%
0.0%
-0.2%
-0.4%
-0.6%
-0.8%
-1.0%
0.0
0.5
1.0
IOUT (A)
12
14
1.5
16
18
2.0
Efficiency
Efficiency (%)
100
90
80
70
60
50
40
30
20
10
0
VOUT=3.3V
VOUT=5V
0.0
AP1534 Rev. 5
0.5
1.0
IOUT (A)
1.5
2.0
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Typical Performance Characteristics
(Continued)
Vout Ripple
(Vin=5V, Vout=3.3V, Iout=0.1A)
Vout Ripple
(Vin=5V, Vout=3.3V, Iout=2A)
Test Circuit
VCC
OUTPUT
FB
Oscillation
open
open
OCSET
A
EN
+
-
VSS
Enable function test
VCC
+
-
A
OUTPUT
VCC
OUTPUT
OCSET
EN
FB
VSS
Feedback function test
FB
OCSET
EN
VSS
+
V
-
Operation function test
AP1534 Rev. 5
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Functional Description
PWM Control
The AP1534 is a DC/DC converter that employs pulse width
modulation (PWM) scheme. Its pulse width varies in the range of
0% to 99%, based on the output current loading. The output
ripple voltage caused by the PWM high frequency switching can
easily be reduced through an output filter. Therefore, this
converter provides a low ripple output supply over a broad range
of input voltage & output current loading
Inductor Selection
For most designs, the operates with inductors of 22µH to
33µH. The inductor value can be derived from the following
equation:
Under Voltage Lockout
The under voltage lockout circuit of the AP1534 assures that the
high-side MOSFET driver remains in the off state whenever the
supply voltage drops below 3.3V. Normal operation resumes
once VCC rises above 3.5V.
Where ΔIL is inductor Ripple Current. Large value inductors lower
ripple current and small value inductors result in high ripple
current. Choose inductor ripple current approximately 15% of the
maximum load current 2A, ∆IL=0.3A. The DC current rating of the
inductor should be at least equal to the maximum load current
plus half the ripple current to prevent core saturation (2A+0.15A).
Current Limit Protection
The current limit threshold is set by external resistor ROCSET
connected from VCC supply to OCSET pin. The internal sink
current IOCSET (90uA typical) across this resistor sets the voltage
at OCSET pin. When the PWM voltage is less than the voltage at
OCSET, an over-current condition is triggered.
The current limit threshold is given by the following equation:
IPEAK × RDS(ON) = IOCSET × ROCSET
where,
VIN − VOUT VOUT
×
FS × L
VIN
The bulk capacitor’s ESR will determine the output ripple voltage
and the initial voltage drop after a high slew-rate transient.
The above equation is recommended for input voltage range of
5V to 18V. For input voltage lower than 5V or ambient
temperature over 100°C, higher ROCSET is recommended.
The recommended minimum ROCSET value is summarized below:
AP1534 Rev. 5
VOUT (V)
1
3.3
5
12
ROCSET (Ω)
6.8K
5.6K
3.9K
4.7K
Input Capacitor Selection
This capacitor should be located close to the IC using short leads
and the voltage rating should be approximately 1.5 times the
maximum input voltage. The RMS current rating requirement for
the input capacitor of a buck regulator is approximately 1⁄2 the
DC load current. A low ESR input capacitor sized for maximum
RMS current must be used. A 470µF low ESR capacitor for most
applications is sufficient.
VRIPPLE = ΔIL × ESR
IPEAK is the output peak current; RDS (ON) is the MOSFET ON
resistance; FS is the PWM frequency (300KHz typical). Also, the
inductor value will affect the ripple current ΔI.
VIN (V)
4
5
12
18
VIN − VOUT VOUT
×
fS × ΔI
VIN
Output Capacitor Selection
The output capacitor is required to filter the output voltage and
provides regulator loop stability. The important capacitor
parameters are the 100KHz Equivalent Series Resistance (ESR),
the RMS ripples current rating, voltage rating and capacitance
value. For the output capacitor, the ESR value is the most
important parameter. The output ripple can be calculated from
the following formula.
( ΔI)
IPEAK > IOUT (MAX) + 2
ΔI =
L=
An aluminum electrolytic capacitor's ESR value is related to the
capacitance and its voltage rating. In most case, higher voltage
electrolytic capacitors have lower ESR values. Most of the time,
capacitors with much higher voltage ratings may be needed to
provide the low ESR values required for low output ripple voltage.
PCB Layout Guide
If you need low TC & TJ or large PD (Power Dissipation), The dual
SW pins(5& 6) and Vss pins(7& 8)on the SOP-8L package are
internally connected to die pad, The evaluation board should be
allowed for maximum copper area at output (SW) pins.
1. Connect FB circuits (RA, RB, CC) as closely as possible and
keep away from inductor flux for pure VFB.
2. Connect CVCC to Vcc and Vss pin as closely as possible to get
good power filter effect.
3. Connect ROCSET to Vcc and OCSET pin as closely as possible.
4. Connect ground side of the CIN & D1 & COUT as closely as
possible and use ground plane for best performance.
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Functional Description
(Continued)
Connect FB circuits closer and keep away from L1.
Top Side Layout Guide
Use vias to conduct the heat into the backside of PCB
layer. The heat sink at output (SW) pins should be
allowed for maximum solder-painted area.
Bottom Side Layout Guide
AP1534 Rev. 5
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Functional Description
(Continued)
Vcc
VIN
R4
+
-
Output
C7
Option
C2
AP1534
FB
OCSET
+ C3
-
C6
C1
Option
VOUT
R1
+
V SS
EN
R5
L1
C8
+
-
D1
C4
R2
Figure: Layout numbering comparison.
Marking Information
(1) SOP-8L
( Top View )
8
5
Logo
Part Number
AP1534
YY WW X X
1
AP1534 Rev. 5
G : Green
YY : Year : 08, 09,10~
represents 52 and 53 week
WW : Week : 01~52; 52
X : Internal Code
4
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AP1534
PWM CONTROL 2A STEP-DOWN CONVERTER
Package Information
(All Dimensions in mm)
0.254
0.10/0.20
3.85/3.95
5.90/6.10
(1) Package Type: SOP-8L
Gauge Plane
Seating Plane
0.62/0.82
Detail "A"
7°~9°
0.15/0.25
1.30/1.50
1.75max.
0.35max. 45°
7°~9°
Detail "A"
0°/8°
0.3/0.5
1.27typ
4.85/4.95
5.4
8x-0.60
8x-1.55
6x-1.27
Land Pattern Recommendation
(Unit: mm)
IMPORTANT NOTICE
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further
notice to any product herein. Diodes Incorporated does not assume any liability arising out of the application or use of any product described herein; neither
does it convey any license under its patent rights, nor the rights of others. The user of products in such applications shall assume all risks of such use and will
agree to hold Diodes Incorporated and all the companies whose products are represented on our website, harmless against all damages.
LIFE SUPPORT
Diodes Incorporated products are not authorized for use as critical components in life support devices or systems without the expressed written approval of the
President of Diodes Incorporated.
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