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AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Features
* * * * * * * * * * Input voltage: 4V to 23V Output voltage: 0.8V to VCC Output current: 1.8A up to peak 2A Duty ratio: 0% to 99% PWM control Oscillation frequency: 300KHz typ. Soft-start like, Current limit and 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)
General Description
AP1533 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. AP1533 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 minimum 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-package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 23V, it is also suitable for the operation via an AC adapter.
Applications
* * * * * * * * PC Motherboard LCD Monitor Graphic Card DVD-Video Player Telecom Equipment ADSL Modem Printer and other Peripheral Equipment Microprocessor core supply
Ordering Information
AP1533 X X X Package S : SOP-8L Lead Free G : Green Packing -U : Tube -13 : Taping
Note:
1. RoHS revision 13.2.2003. Glass and High Temperature Solder Exemptions Applied, see EU Directive Annex Notes 5 and 7.
Device
AP1533S
Note:
Package Packaging Code (Note 2)
S SOP-8L
Tube/Bulk Quantity Part Number Suffix
100 -U
13" Tape and Reel Quantity Part Number Suffix
2500/Tape & Reel -13
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.
AP1533 Rev. 1
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JULY 2007
(c) Diodes Incorporated
AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Pin Assignments
FB 1 EN 2 AP1533 OCSET 3 VCC 4
8 7 6 5
VSS VSS Output Output
Pin Descriptions
Pin Name FB Pin No. 1 Description Feedback pin Power-off pin H: Normal operation (Step-down operation) L: Step-down operation stopped (All circuits deactivated) Add an external resistor to set max output current IC power supply pin Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin to reduce EMI GND Pin
EN
2
OCSET VCC Output VSS
3 4 5, 6 7, 8
AP1533 Rev. 1
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(c) Diodes Incorporated
AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Block Diagram
Output Oscillation Circuit VCC PWM-Switched Control Circuit Thermal Shutdown VEN 90uA VSS + FB Reference Voltage Source
EN
OCSET
Absolute Maximum Ratings
Symbol VCC VFB VEN VOUT PD TJ TST
Caution:
Parameter VCC Pin Voltage Feedback Pin Voltage EN Pin Voltage Switch Pin Voltage Power Dissipation Operating Junction Temperature Range Storage Temperature Range
Rating VSS - 0.3 to VSS + 24 VSS - 0.3 to VCC VSS - 0.3 to VIN + 0.3 VSS - 0.3 to VIN + 0.3 Internally limited -20 to +125 -65 to +150
Unit V V V V mW
o o
C C
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 Parameter Input Voltage Output Current Operating Ambient Temperature Min 4 0 -25 Max 23 1.8 85 Unit V A o C
AP1533 Rev. 1
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(c) Diodes Incorporated
AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Electrical Characteristics
( VIN = 12V, TA = 25C, unless otherwise specified ) Symbol Parameter Conditions VFB Feedback Voltage IOUT = 0.1A IFB Feedback Bias Current IOUT = 0.1A Current Consumption During ISHDN VEN = 0V Power Off VOUT Line Regulation / VIN VOUT Load Regulation / VOUT fOSC Oscillation Frequency Frequency of Current Limit or fOSC1 Short Circuit Protection VIH EN Pin Input Voltage VIL ISH EN Pin Input Leakage Current ISL IOCSET OCSET Pin Bias Current RDS(ON) Internal MOSFET RDS(ON) EFFI TSHDN THYS JA JC
Note:
Min 0.784 240 2.0 75 -
Typ. 0.8 0.1 10 1 0.2 300 50 20 -10 90 110 80 91 150 55 134 22
Max 0.816 0.5 2 0.5 400 0.8 105 150 110 -
Unit V A A % % KHz KHz V A A A m % C C
o
VIN = 5V~23V IOUT = 0.1 to 1.8A Measure waveform at SW pin Measure waveform at SW pin Evaluate oscillation at SW pin Evaluate oscillation stop at SW pin EN Pin High EN Pin Low -VIN=5V, VFB=0V VIN=12V, VFB=0V VIN=12V, VOUT = 5V IOUT=1.8A
Efficiency
Thermal shutdown threshold Thermal shutdown hysteresis Thermal Resistance SOP-8L (Note 3) Junction-to-Ambient Thermal Resistance SOP-8L (Note 3) Junction-to-Case
C/W C/W
o
3. Test condition: Device mounted on FR-4 PCB, 2"x2", 2oz copper, minimum recommended pad layout, single side. For better thermal performance, larger copper pad for heatsink is needed.
AP1533 Rev. 1
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(c) Diodes Incorporated
AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Typical Application Circuit
L1 Output 33uH ROCSET COCSET 3.3K Option CIN 470uF CVcc 0.1uF REN 100K CEN 0.1uF OCSET EN VSS D1 (Note 4) RB 1.3K RA 6.8K VOUT=5V/1.8A
VIN
Vcc
AP1533
FB
CC Optional
+ -
C
+ -
COUT 470uF
0.1uF
V OUT = VFB x (1+R A/RB) R B = 0.7K~5K ohm
Note: 4. Suggested DIODES Power Schottky P/N: B340 series or PDS340.
Typical Performance Characteristics
VIN vs. Frequency
320 318 316 314 312 310 308 306 304 302 300 0 2 4 (VOUT=3.3V; IOUT=0.2A)
VIN vs. VFB
0.820 0.815 0.810 0.805 0.800 0.795 0.790 0.785 0.780 (VOUT=3.3V; IOUT=0.2A)
FOSC (kHz)
6
8
10 12 14 16 18 20 22 24 VIN (V)
VFB (V)
0
2
4
6
8
10 12 14 16 18 20 22 24 VIN (V)
AP1533 Rev. 1
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AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Typical Performance Characteristics
Line Regulation
3.40 3.35 3.30 (VOUT=3.3V; IOUT=0.2A)
( Continued )
Load Regulation
3.25 3.24 3.23 3.22 3.21 3.20 3.19 3.18 3.17 3.16 3.15 0 0.5 (VIN=12V)
VOUT (V)
3.20 3.15 3.10 3.05 3.00 0 2 4 6 8 10 12 14 16 18 20 22 24 VIN (V)
VOUT (V)
3.25
1 IOUT (A)
1.5
2
Efficiency
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0 0.5 1 IOUT (A) 1.5
Efficiency (%)
VOUT=3.3V VOUT=5V
2
VOUT Ripple ( VIN = 12V; VOUT = 3.3V; IOUT = 0.1A )
VOUT Ripple (VIN = 12V; VOUT = 3.3V; IOUT = 1.8A )
AP1533 Rev. 1
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(c) Diodes Incorporated
AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Test Circuit
Oscillation open VCC OUTPUT FB open
A
VCC
OUTPUT
FB
OCSET
A
+
EN
VSS
-
OCSET EN
VSS
Enable function test
Feedback function test
VCC
+ -
OUTPUT
FB
OCSET EN VSS
+ V
Operation function test
Function Description
PWM Control The AP1533 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 Under Voltage Lockout The under voltage lockout circuit of the AP1533 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. 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 x RDS(ON) = IOCSET x R OCSET
( I) IPEAK > IOUT (MAX) + 2
where,
I =
VIN - VOUT FSxL
x
VOUT VIN
IPEAK is the output peak current; RDS (ON) is the MOSFET ON resistance (115m typical); FS is the PWM frequency (300KHz typical). Also, the inductor value will affect the ripple current I. The above equation is recommended for input voltage range of 5V to 18V. For input voltage lower than 5V, higher than 18V or ambient temperature over 100C, ROCSET3.9K is recommended. The recommended minimum ROCSET value is summarized below: VOUT (V) ROCSET () VIN (V) 4 0.8 3.9K 5 3.3 3.3K 12 5 3.3K 18 12 3.3K 23 12 4.7K The maximum ROCSET value should not exceed AP1533 maximum current output.
AP1533 Rev. 1
7 of 8 www.diodes.com
JULY 2007
(c) Diodes Incorporated
AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
Marking Information
(Top View)
8 5
Logo Part No.
G : Green
AP1533 YY WW X X
1 4
Internal code Xth week : 01~52 Year : "07" = 2007 "08" = 2008
~
SOP-8L
Package Information
Package Type: SOP-8L
(unit: mm )
3.70/4.10
5.79/6.20
0.08/0.25
0.254 0.38/1.27
Gauge Plane Seating Plane
Detail "A"
7~9 1.30/1.50 1.75max. 0.20typ 7~9
0.35max. 45
Detail "A"
3.70/4.10
1.27typ 4.80/5.30
0.3/0.5
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.
AP1533 Rev. 1
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JULY 2007
(c) Diodes Incorporated

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