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AP1518
300KHz, 3A PWM Buck DC/DC Converter Features
- Adjustable version output voltage range, 0.8V to 18V+4% - 300KHz +15% fixed switching frequency - Voltage mode non-synchronous PWM control - Thermal-shutdown and current-limit protection - ON /OFF shutdown control input - Operating voltage can be up to 22V - Output load current: 3A - TO220-5L and TO263-5L Pb-Free packages - Low power standby mode - Built-in switching transistor on chip
General Description
The AP1518 series are monolithic IC designed for a step-down DC/DC converter, and own the ability of driving a 3A load without external transistor. Due to reducing the number of external component, the board space can be saved easily. The external shutdown function can be controlled by logic level and then come into standby mode. The internal compensation makes feedback control have good line and load regulation without external design. Regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is to prevent over current operating of the output switch. If current limit function occurred and VFB is down to 0.5V below, the switching frequency will be reduced. The AP1518 series operate at a switching frequency of 300KHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Other features include a guaranteed +4% tolerance on output voltage under specified input voltage and output load conditions, and +15% on the oscillator frequency. The packages are available in a standard 5-lead TO-220 package or a 5-lead TO-263.
Applications
- Simple High-efficiency step-down regulator - On-card switching regulators - Positive to negative converter
Pin Assignments
( Top View ) 5 SD 4 FB 3 Gnd 2 Output 1 VIN
Pin Descriptions
Name VIN Output GND FB SD Description Operating voltage input Switching output Ground Output voltage feedback control
ON /OFF Shutdown
Metal Tab GND
TO263-5L ( Top View ) 5 SD 4 FB 3 Gnd 2 Output 1 VIN TO220-5L
This datasheet contains new product information. Anachip Corp. reserves the rights to modify the product specification without notice. No liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
Rev.1.1 Oct 29, 2004 1/12
AP1518
300KHz, 3A PWM Buck DC/DC Converter Ordering Information
AP1518 XX Packing Blank : Tube A : Taping
Package T5: TO220-5L K5: TO263-5L T5R: TO220-5L(R)
Block Diagram
SD
VIN
200mV Current Source bias 0.8V Reference 2.5V Regulator Start up 220mV
Comp _
+
Comp
+
FB
_
Comp
+
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_
Amp
+
Frequecy compensation
Pre-driver
300kHz OSC.
Thermal Shutdown
_
3A Switch
Output Gnd
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Absolute Maximum Ratings
Symbol VCC VSD VFB VOUT PD TST TOP VOP Parameter Supply Voltage
ON /OFF Pin input voltage Feedback Pin voltage Output voltage to Ground Power dissipation Storage temperature Operating temperature Operating voltage
Rating +24 -0.3 to +18 -0.3 to +18 -1 Internally limited -65 to +150 -40 to +125 +4.5 to +22
Unit V V V V W o C o C V
Electrical Characteristics (All Output Voltage Versions)
Unless otherwise specified, VIN=12V, ILOAD = 0.5A
Symbol IFB FOSC FSCP VSAT DC ICL IL IQ ISTBY VIL VIH IH IL JC JA
Parameter Feedback bias current Oscillator frequency
Conditions VFB=0.8V (Adjustable version only)
Min. 255 220 10
Typ. -10 300 30 1.4 100 0
Max. -50 -100 345 345 50 1.6 1.7
Unit nA KHz KHz V %
of When current limit occurred o and VFB < 0.5V, Ta=25 C IOUT=3A Saturation Voltage No outside circuit VFB=0V force driver on Max. Duty Cycle (ON) VFB=0V force driver on Min. Duty Cycle (OFF) VFB=12V force driver off Peak current Current limit No outside circuit VFB=0 force driver on Output No outside circuit Output = 0V leakage VFB=12 force driver off current VIN=22V Output =-1V Quiescent Current VFB=12 force driver off Standby Quiescent ON /OFF pin=5V Current VIN=22V Low (regulator ON) ON /OFF pin logic input High (regulator OFF) threshold voltage
ON /OFF pin logic input current ON /OFF pin input current
Oscillator frequency short circuit protect
5.5 3.6 4.5 6.5 -200 -5 5 70 2.0 1.3 10 150 200 0.6 -0.01 uA -0.1 2.5 3.5 28 23 -1
o
A uA mA mA uA V
VLOGIC=2.5V (OFF) VLOGIC=0.5V (ON) TO220-5L TO263-5L TO220-5L TO263-5L Junction to case Junction to ambient
Thermal Resistance Thermal Resistance With copper area of approximately 3 in2
C/W C/W
o
Specifications with boldface type are for full operating temperature range, the other type are for TJ=25C.
Anachip Corp. www.anachip.com.tw 3/12
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Electrical Characteristics (Continued)
Sym.
VFB
Parameter Output Feedback Efficiency Efficiency Efficiency Efficiency
Conditions 5V < VIN < 22V 0.2A < ILOAD < 3A VOUT programmed for 3V VIN = 12V, ILOAD=3A VOUT programmed for 3.3V VIN = 12V, ILOAD=3A VOUT programmed for 5V VIN = 12V, ILOAD=3A VOUT programmed for 12V VIN = 16V, ILOAD = 3A
Typ. 0.8 74 75 80 89
Limit 0.784/0.768 0.816/0.832
Unit V VMIN VMAX % % % %
AP1518

Specifications with boldface type are for full operating temperature range, the other type are for TJ=25C.
Anachip Corp. www.anachip.com.tw 4/12
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Typical Performance Characteristics
AP1518 Efficiency v.s. Temperature (Vin=12V,Vout=5V,Io=3A)
83 82 81 80 79 78 77 76 75 74 73 72 -50 -30 -10 10 30 50 70 90 110 130 150
AP1518 Efficiency v.s. Temperature (Vin=12V,Vout=3.3V,Io=3A)
78 77 76
Efficiency (%)
Efficiency (%)
75 74 73 72 71 70 -50 -30 -10 10 30 50 70 90 110 130 150
Temperature (TA) (C)
Temperature (TA) (C)
AP1518 Saturation Voltage v.s. Temperature (Vcc=12V,Vfb=0V,VSD=0)
1.6 1.5
AP1518 Switch Current Limit v.s. Temperature (Vcc=12V,Vfb=0V)
5.5
Saturation Voltage (V)
1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 -50 -25 0 25 1A 0.5A
3A 2A
Switch Current Limit (A)
5 4.5 4 3.5 3 -50 -30 -10 10 30 50 70 90
50
75
100
125
Temperature (TA)(C)
Temperature (TA) (C)
AP1518 Supply Current v.s. Temperature (Vcc=12V , No Load ,Von/off =0V(Switch ON) ,Von/off =5V(Switch OFF))
15 14 13 12 11 10 9 8 7 6 5
60
Supply Current (mA)
Supply Current (uA)
55 50 45 40 35 30 -50 -30 -10 10 30 50 70 90 110 130 150 Switch OFF
Switch ON
-50 -30 -10 10
30
50
70
90 110 130 150
Temperature (TA) (C)
Temperature (TA) (C)
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Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Typical Performance Characteristics (Continued)
AP1518 Threshold Voltage v.s. Temperature (Vcc=12V , Io=100mA)
1.7 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 -50 -30 -10 10 30 50 70 90 110 130 150
AP1518 ON/OFF Current v.s. ON/OFF Voltage (Vin=12V)
10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 0 3 6 9 12 15 18 21
Threshold Voltage (V)
Temperature (TA) (C)
ON/OFF Current (nA)
ON/OFF Voltage (V)
AP1518 Frequency v.s. Temperature (Vcc=12V , Io=500mA ,Vout=5V)
320
AP1518 Feedback Current v.s. Temperature (Vcc=12V , Vout=5V,Vfb=0.8V)
10
300 290 280 270 260 -50 -30 -10 10 30
Feedback Current (nA)
50 70 90 110 130 150
310
0 -10 -20 -30 -40 -50 -50 -30 -10 10
Frequency (KHz)
Temperature (TA) (C)
Temperature (TA) (C)
30
50
70
90 110 130 150
AP1518 Output Voltage v.s. Temperature (Vin=12V ,Io=3A)
3.5 3.45 3.4 3.35 3.3 3.25 3.2 3.15 3.1 3.05 3 2.95 2.9 -40 -20 0
Vout (V)
Temperature (TA) (C)
20
40
60
80 100 120 140 160
Anachip Corp. www.anachip.com.tw 6/12
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Typical Application Circuit
(1) Normal Circuit
R2 FB 12V DC Input Vin Cin Capacitor 4 1 AP1518 5 SD 3 Gnd D1 Schottky Diode Co Capacitor 2 Output L1 10uH 1V/ 2A Output Load R1
Vout = VFB x (1 + VFB = 0.8V R2 = 1K ~ 3K (2) Delay Start Circuit
R2 FB 12V DC Input Vin Cin Capacitor CDELAY 0.1uF 4 1 5 SD RDELAY 10K AP1518 3 2
R1 R2
)
R1
Output
L1 10uH
1V/ 2A Output Load
Gnd
D1 Schottky Diode
Co Capacitor
Anachip Corp. www.anachip.com.tw 7/12
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Function Description
Pin Functions +VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Ground Circuit ground. Output Internal switch. The voltage at this pin switches between (+VIN - VSAT) and approximately - 0.5V, with a duty cycle of approximately VOUT / VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept a minimum. Feedback (FB) Senses the regulated output voltage to complete the feedback loop.
ON /OFF (SD) Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 150uA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 18V) shuts the regulator down. If this shutdown
of 25oC (still air). These temperature rise numbers are all approximate and there are many factors that can affect these temperatures. Higher ambient temperatures require more heat sinking. The TO-263 surface mount package tab was designed to be soldering to the copper on a printed circuit board. The copper and the board are the heat sink for this package and the other heat producing components, such as the catch diode and inductor. The PC board copper area that the package is soldered to should be at least 0.8 in2, and ideally should have 2 or more square inches of 2 oz. Additional copper area improves the thermal characteristics, but with copper areas greater than approximately 6 in2, only small improvements in heat dissipation are realized. If further thermal improvements are needed, double sided, multi-layer PC board with large copper areas and/or airflow will be recommended. The AP1518 (TO-263 package) junction temperature rises above ambient temperature with a 2A load for various input and output voltages. This data was taken with the circuit operating as a buck-switching regulator with all components mounted on a PC board to simulate the junction temperature under actual operating conditions. This curve can be used for a quick check for the approximate junction temperature for various conditions, but be aware that there are many factors that can affect the junction temperature. When load currents higher than 3A are used, double sided or multi-layer PC boards with large copper areas and/or airflow might be needed, especially for high ambient temperatures and high output voltages. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (Once exception to this is the output (switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further.
feature is not needed, the ON /OFF pin can be wired to the ground pin. Thermal Considerations The AP1518 is available in two packages: a 5-pin TO-220 and a 5-pin surface mount TO-263. The TO-220 package needs a heat sink under most conditions. The size of the heatsink depends on the input voltage, the output voltage, the load current and the ambient temperature. The AP1518 junction temperature rises above ambient temperature for a 3A load and different input and output voltages. The data for these curves was taken with the AP1518 (TO-220 package) operating as a buck-switching regulator in an ambient temperature
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Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Function Description (Continued)
Package thermal resistance and junction temperature rise numbers are all approximate, and there are many factors that will affect these numbers. Some of these factors include board size, shape, thickness, position, location, and even board temperature. Other factors are, trace width, total printed circuit copper area, copper thickness, single or double-sided, multi-layer board and the amount of solder on the board. The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such as the catch diode will add heat to the PC board and the heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board.
Marking Information
(1) TO263-5L
( Top view )
(2) TO220-5L
( Top view )
Logo Part Number
1518 YY WW X
Logo
ID code Xth week: 01~52 Year: "01" = 2001 "02" = 2002
Part Number
1518 YY WW X
ID code Xth week: 01~52 Year: "01" = 2001 "02" = 2002
~
~
Anachip Corp. www.anachip.com.tw 9/12
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Package Information
(1) Package Type: TO220-5L
E P H1 Q
A
F
L
D
e e1
b
C J1
Symbol A b C D E e e1 F H1 J1 L Op Q
Dimensions In Millimeters Min. Nom. Max. 4.07 4.45 4.82 0.76 0.89 1.02 0.36 0.50 0.64 14.22 14.86 15.50 9.78 10.16 10.54 1.57 1.71 1.85 6.68 6.81 6.93 1.14 1.27 1.40 5.46 6.16 6.86 2.29 2.74 3.18 13.21 13.97 14.73 3.68 3.81 3.94 2.54 2.73 2.92
Dimensions In Inches Min. Nom. Max. 0.160 0.030 0.014 0.560 0.385 0.062 0.263 0.045 0.215 0.090 0.520 0.145 0.100 0.175 0.035 0.020 0.585 0.400 0.067 0.268 0.050 0.243 0.108 0.550 0.150 0.107 0.190 0.040 0.025 0.610 0.415 0.073 0.273 0.055 0.270 0.125 0.580 0.155 0.115
Anachip Corp. www.anachip.com.tw 10/12
Rev.1.1 Oct 29, 2004
AP1518
300KHz, 3A PWM Buck DC/DC Converter Package Information (Continued)
(2) Package Type: TO263-5L
E L2 10.9
9.1
L
1.0 1.7 e B
Land Pattern Recommendation (Unit: mm)
2.5 C L1
Symbol A B C C2 D E e L L1 L2
Dimensions In Millimeters Min. Nom. Max. 4.07 4.46 4.85 0.66 0.84 1.02 0.36 0.50 0.64 1.14 1.27 1.40 8.65 9.15 9.65 9.78 10.16 10.54 1.57 1.71 1.85 14.61 15.24 15.88 2.29 2.54 2.79 2.92
Dimensions In Inches Min. Nom. Max. 0.160 0.176 0.191 0.026 0.033 0.040 0.014 0.020 0.025 0.045 0.050 0.055 0.341 0.360 0.380 0.385 0.400 0.415 0.062 0.068 0.073 0.575 0.600 0.625 0.090 0.100 0.110 0.115
Anachip Corp. www.anachip.com.tw 11/12
C2
Rev.1.1 Oct 29, 2004
A
15.7
D
AP1518
300KHz, 3A PWM Buck DC/DC Converter Package Information (Continued)
(3) Package Type: TO220-5L(R) Mechanical drawing
E Q A F
H1
D d1 H2 H3
d2
J1 b e J2 J3
J3 J2 J1 E A
Symbol A b D d1 d2 E e F H1 H2 H3 J1 J2 J3 Q
Dimensions In Millimeters Min. Nom. Max. 4.4 4.6 4.7 0.7 0.8 0.9 8.4 8.7 8.9 1.0 6.3 9.91 10.16 10.41 1.6 1.7 1.8 1.2 1.25 1.3 6.4 20.8 21.6 22.4 23.9 24.7 25.5 2.7 3.7 4.5 5.3 8.4 2.5 2.8 3.0
Dimensions In Inches Min. Nom. Max. 0.175 0.180 0.185 0.027 0.032 0.037 0.330 0.340 0.350 0.039 0.248 0.390 0.400 0.410 0.062 0.067 0.072 0.048 0.050 0.052 0.250 0.820 0.850 0.880 0.942 0.972 1.002 0.105 0.147 0.177 0.207 0.331 0.100 0.110 0.120
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Rev.1.1 Oct 29, 2004

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