UMW
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UMW AP1501
FEATURES
GENERAL DESCRIPTION
The AP1501 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 3A load with
excellent line and load regulation. These devices are available
in fixed output voltages of 3.3V, 5V, 12V, and an adjustable
output version.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation, and a fixed-frequency oscillator.
The AP1501 series operates at a switching frequency of 150
kHz thus allowing smaller sized filter components than what
would be needed with lower frequency switching regulators.
Available in a standard 5-lead TO-220 package with several
different lead bend options, and a 5-lead TO-263 surface mount
package.
A standard series of inductors are available from several
different manufacturers optimized for use with the AP1501
series. This feature greatly simplifies the design of switch-mode
power supplies.
Other features include a guaranteed ±4% tolerance on output
voltage under specified input voltage and output load
conditions, and ±15% on the oscillator frequency. External
shutdown is included, featuring typically 80 µA standby
current. Self protection features include a two stage frequency
reducing current limit for the output switch and an over
temperature shutdown for complete protection under fault
conditions.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
3.3V, 5V, 12V, and adjustable output versions
Adjustable version output voltage range, 1.2V to 37V
±4% max over line and load conditions
Available in TO-220 and TO-263 packages
Guaranteed 3A output load current
Input voltage range up to 40V
Requires only 4 external components
Excellent line and load regulation specifications
150 kHz fixed frequency internal oscillator
TTL shutdown capability
Low power standby mode, IQ typically 80 µA
High efficiency
Uses readily available standard inductors
Thermal shutdown and current limit protection
APPLICATIONS
•
•
•
Simple high-efficiency step-down (buck) regulator
On-card switching regulators
Positive to negative converter
TYPICAL APPLICATION (Fixed Output Voltage Versions)
12V
4
AP 1501
5.0
+ 1
2
CIN
5
3
680µF
+VIN
L1
5.0V
+C
OUT
220µF
BLOCK DIAGRAM
ON/ OFF
VIN
START
UP
2.5V
+
+
+
COM
COM
+
FEEDBACK
R2
GM
+
AMP
Active
capacitor
LATCH
DRIVER
+
+
OUTPUT
150kHz
OSC
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GND
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PIN FUNCTIONS
ABSOLUTE MAXIMUM RATINGS (Note 1)
+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 to a minimum.
Feedback —Senses the regulated output voltage to complete
the feedback loop.
ON/OFF - Allows the switching regulator circuit to be shut
down using logic level signals thus dropping the total input
supply current to approximately 80 µA. 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 25V)
shuts the regulator down. If this shutdown feature is not needed,
the ON /OFF pin can be wired to the ground pin or it can be left
open, in either case the regulator will be in the ON condition.
Maximum Supply Voltage
45V
ON /OFF Pin Input Voltage -0.3 ≤ V ≤ +25V
Feedback Pin Voltage
-0.3 ≤ V ≤+25V
Output Voltage to Ground
(Steady State)
-1V
Power Dissipation
Internally limited
Storage Temperature Range -650C to +1500C
ESD Susceptibility
Human Body Model (Note 2)
2 kV
Lead Temperature
S Package
Vapor Phase (60 sec.)
+2150C
Infrared (10 sec.)
+2450C
T Package (Soldering, 10 sec.)
+2600C
Maximum Junction Temperature
+1500C
OPERATING CONDITIONS
Temperature Range
Supply Voltage
-400C≤TJ≤+1250C
4.5V to 40V
AP1501-3.3
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 250C, and those with boldface type apply over full Operating Temperature
Range
AP1501-3.3
Units
Symbol
Parameter
Conditions
Typ
Limit
(Limits)
(Note 3)
(Note 4)
SYSTEM PARAMETERS (Note 5)Test Circuit Figure 1
VOUT
Output Voltage
3.3
V
4.7V5≤VIN≤40V, 0.2A≤ILOAD≤3A
V(min)
3.168/3.135
V(max)
3.432/3.465
Efficiency
VIN=12V, ILOAD=3A
73
%
η
AP1501-5.0
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 250C, and those with boldface type apply over full Operating Temperature
Range
AP1501-5.0
Units
Symbol
Parameter
Conditions
Typ
Limit
(Limits)
(Note 3)
(Note 4)
SYSTEM PARAMETERS (Note 5)Test Circuit Figure 1
VOUT
Output Voltage
5.0
V
7V≤VIN≤40V, 0.2A≤ILOAD≤3A
V(min)
4.800/4.750
V(max)
5.200/5.250
Efficiency
VIN=12V, ILOAD=3A
80
%
η
AP1501-12
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 250C, and those with boldface type apply over full Operating Temperature
Range
AP1501-12
Units
Symbol
Parameter
Conditions
Typ
Limit
(Limits)
(Note 3)
(Note 4)
SYSTEM PARAMETERS (Note 5)Test Circuit Figure 1
12.0
V
VOUT
Output Voltage
15V≤VIN≤40V, 0.2A≤ILOAD≤3A
V(min)
11.52/11.40
V(max)
12.48/12.60
Efficiency
VIN=12V, ILOAD=3A
90
%
η
AP1501-ADJ
ELECTRICAL CHARACTERISTICS
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Specifications with standard type face are for TJ = 250C, and those with boldface type apply over full Operating
Temperature Range
AP1501-ADJ
Symbol
Parameter
Conditions
Typ
Limit
(Note 3)
(Note 4)
SYSTEM PARAMETERS (Note 5)Test Circuit Figure 1
VOUT
Output Voltage
1.230
4.5V≤VIN≤40V, 0.2A≤ILOAD≤3A
1.193/1.180
VOUT programmed for 3V. Circuit of
1.267/1.280
Figure 1.
Efficiency
VIN=12V, VOUT=3V, ILOAD=3A
73
η
Units
(Limits)
V
V(min)
V(max)
%
ALL OUTPUT VOLTAGE VERSIONS
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 250C, and those with boldface type apply over full Operating Temperature
Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version. ILOAD
= 500 mA
AP1501-XX
Units
Symbol
Parameter
Conditions
Typ
Limit
(Limits)
(Note 3)
(Note 4)
DEVICE PARAMETERS
Feedback Bias Current
Adjustable Version Only, VFB=1.3V
10
nA
Ib
nA (max)
50/100
fO
Oscillator Frequency
(Note 6)
150
kHz
kHz (min)
127/110
kHz (max)
173/173
VSAT
Saturation Voltage
IOUT=3A (Notes 7, 8)
1.16
V
V (max)
1.4/1.5
DC
Max Duty Cycle (ON)
(Note 8)
100
%
Min Duty Cycle (OFF)
(Note 9)
0
ICL
Current Limit
Peak Current (Notes 7, 8)
4.5
A
A (min)
3.6/3.4
A (max)
6.9/7.5
IL
Output Leakage Current
Output=0V (Notes 7, 9)
50
µA (max)
Output=-0.9V (Note 10)
10
mA
30
mA (max)
IQ
Quiescent Current
(Note 9)
5
mA
10
mA (max)
ISTBY
Standby Quiescent
ON/OFF pin=5V (OFF) (Note 10)
80
µA
Current
200/250
µA (max)
0
Thermal Resistance
TO-220 or TO-263 Package, Junction to Case
2
C/W
θJC
0
TO-220 Package, Junction to Ambient (Note 11)
50
C/W
θJA
0
TO-263 Package, Junction to Ambient (Note 12)
50
C/W
θJA
0
TO-263 Package, Junction to Ambient (Note 13)
30
C/W
θJA
0
C/W
TO-263 Package, Junction to Ambient (Note 14)
20
θJA
ON/OFF CONTROL Test Circuit Figure 1
1.3
V
ON/OFF Pin Logic Input
V (max)
Threshold Voltage
Low (Regulator ON)
VIH
0.6
V (min)
High (Regulator OFF)
VIL
2.0
IH
ON/OFF Pin Input Current VLOGIC=2.5V (Regulator OFF)
5
µA
15
µA (max)
IL
VLOGIC=0.5V (Regulator ON)
0.02
µA
5
µA (max)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate
conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed
specifications and test conditions, see the Electrical Characteristics.
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 3: Typical numbers are at 250C and represent the most likely norm.
Note 4: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room
temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard
Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can
affect switching regulator system performance. When the AP1501 is used as shown in the Figure 1 test circuit, system performanc e
will be as shown in system parameters section of Electrical Characteristics.
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Note 6: The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is
determined by the severity of current over-load.
Note 7: No diode, inductor or capacitor connected to output pin.
Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
Note 9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V
version, to force the output transistor switch OFF.
Note 10: VIN = 40V.
Note 11: Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with the leads
soldered to a printed circuit board with (1 oz.) copper area of approximately 1 in2
Note 12: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single printed circuit board with 0.5 in2
of (1 oz.) copper area.
Note 13: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with
2.5 in2 of (1 oz.) copper area.
Note 14: Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with
3 in2 of (1 oz.) copper area on the AP1501S side of the board, and approximately 16 in 2 of copper on the other side of the p-c
board.
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 1)
Normalized Output Voltage
Line Regulation
1.5
Efficiency
95
1.0
0.5
0.1
0
0
-0.1
-0.5
EFFICIENCY (%)
0.4
0.3
0.2
-0.2
-1.0
-50 -25
0
-0.3
-0.4
0
25 50 75
80
5V
75
70
SWITCH CURRENT LIMIT (A)
SATURATION VOLTAGE (V)
VIN=12V
1.3
1.2
1.1
0
TJ=-40 C
1.0
0.9
0.8
0
0.7 25 C
0
125 C
0.6
0
1
2
3
4
3.3V
65
5 10 15 20 25 30 35 40
0
5.5
VIN = 12V
VOUT=5V
5.0
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
Switch Current Limit
1.4
12V
85
INPUT VOLTAGE (V)
Switch Saturation
Voltage
20V
90
Dropout Voltage
1.6
1.4
1.2
ILOAD=3A
4.5
1.0
4.0
0.8
3.5
-50 -25
0
25 50 75
ILOAD=1A
0.6
-50 -25
0
25 50 75
SWITCH CURRENT (A)
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TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 1) (Continued)
Shutdown
Quiescent Current
120
20
ISWITCH= 0
16
12
8
CURRENT (µA)
SUPPLY CURRENT (mA)
24
_ =5V
VON/
OFF
100
4
0
TJ= 25 C
80
60
40
20
0
-50 -25
0
0
0
25 50 75
ON/OFF Threshold
Voltage
10
20
40
30
SUPPLY VOLTAGE (V)
0.5
CURRENT ( µA)
ON
FREQUENCY (kHz)
6
OFF
1.0
5
4
3
2
1
0
3
2
1
0
-50 -25
0
25 50 75
0
25 50 75
160
7
1.5
4
Switching Frequency
8
2.0
-50 -25
5
ON/OFF Pin
Current (Sinking)
2.5
THRESHOLD vOLTAGE (V)
Minimum Operating
Supply Voltage
SUPPLY VOLTAGE (V)
Operating
Quiescent Current
0
10
__5
15
20
25
155
150
145
140
135
130
-50 -25
0
25 50 75
ON/ OF PIN VOLTAGE (V)
FEEDBACK BIAS CURRENT (nA)
Feedback Pin
Bias Current
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10
7.5
5.0
2.5
ADJUSTABLE VERSION ONLY
0
-2.5
-5.0
-50 -25
0
5
25 50 75
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TYPICAL PERFORMANCE CHARACTERISTICS
Continuous Mode Switching Waveforms
VIN=20V, VOUT=5V, ILOAD=2A
L=32µ
µH, COUT=220µ
µF, COUTESR=50mΩ
Ω
20V
A
B
Discontinuous Mode Switching Waveforms
VIN=20V, VOUT=5V, ILOAD=500mA
L=10µ
µH, COUT=330µ
µF, COUTESR=45mΩ
Ω
20V
10V
A
0V
0V
2A
1A
B
1A
0A
0A
C
10V
C
AC/
div
A: Output Pin Voltage, 10V/ div
B: Inductor Current 1A/ div
C: Output Ri pple Voltage, 50mV/ div
AC/
div
A: Output Pin Voltage, 10V/ div
B: Inductor Current 1A/ div
C: Output Ri pple Voltage, 100mV/ div
Horizontal Time Base: 2 µ s/ div
Horizontal Time Base: 2 µs/ div
Load Transient Response for Continuous Mode
VIN=20V, VOUT=5V, ILOAD=500mA to 2A
L=32µ
µH, COUT=220µ
µF, COUTESR=50mΩ
Ω
Load Transient Response for Discontinuous Mode
VIN=20V, VOUT=5V, ILOAD=500mA to 2A
L=10µ
µH, COUT=330µ
µF, COUTESR=45mΩ
Ω
A
AC
div
A
AC
div
B
1A
B
1A
0A
0A
A: Output Voltage, 100mV/ div. (AC)
B: 500mA to 2A Load Pulse
A: Output Voltage, 100mV/ div.(AC)
B: 500mA to 2A Load Pulse
Horizontal Time Base: 200 µs/ div
Horizontal Time Base: 100 µs/ div
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TEST CIRCUIT AND LAYOUT GUIDELINES
Fixed Output Voltage Versions
4
+ VIN
+
AP1501
+
3
CIN
5
L1
L1
2
+
+
COUT
CIN - 470µF, 50V, Aluminum Electrolytic Nichicon “PL Series”
COUT - 220µF, 25V, Aluminum Electrolytic Nichicon “ PL Series”
D1 - 5A, 40V Schottky Rectifer, 1N5825
L1 - 68µH, L38
Adjustable Output Voltage Versions
CFF
R1
R2
4
+
+ VIN
AP1501
+
3
CIN
5
2
L1
+
COUT
R2
)
R1
where VREF=1.23V
V
R2= R1( OUT -1)
VREF
VOUT=VREF(1+
Select R1 to be approximately 1kΩ, use a 1% resistor for best stability.
CIN - 470µF, 50V, Aluminum Electrolytic Nichicon “PL Series”
COUT - 220µF, 35V, Aluminum Electrolytic Nichicon “ PL Series”
D1 - 5A, 40V Schottky Rectifer, 1N5825
L1 - 68µH, L38
R1 - 1k Ω, 1%
CFF - see Application Information Section
Figure 1. Standard Test Circuits and Layout Guides
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance can generate
voltage transients which can cause problems. For minimal inductance and ground loops, the wires indicated by heavy lines should
be wide printed circuit traces and
should be kept as short as possible. For best results, external components should be located as close to the switcher lC as possible
using ground plane construction or single point grounding.
If open core inductors are used, special care must be taken as to the location and positioning of this type of inductor. Allowing
the inductor flux to intersect sensitive feedback, lC groundpath and COUT wiring can cause problems.
When using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated wiring.
Physically locate both resistors near the IC, and route the wiring away from the inductor, especially an open core type of inductor.
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AP1501 SERIES BUCK REGULATOR DESIGN PROCEDURE (FIXED OUTPUT)
PROCEDURE (Fixed Output Voltage Version)
Given:
VOUT = Regulated Output Voltage (3.3V, 5V or 12V)
VIN (max) = Maximum DC Input Voltage
ILOAD (max) = Maximum Load Current
EXAMPLE (Fixed Output Voltage Version)
Given:
VOUT =5V
VIN (max) = 12V
ILOAD (max) = 3A
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from Figures
Figure 4, Figure 5,or Figure 6. (Output voltages of 3.3V, 5V, or
12V respectively.) For all other voltages, see the design procedure
for the adjustable version.
B. From the inductor value selection guide, identify the inductance
region intersected by the Maximum Input Voltage line and the
Maximum Load Current line. Each region is identified by an
inductance value and an inductor code (LXX).
C. Select an appropriate inductor from the four manufacturer’s part
numbers listed in Figure 8.
1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown in Figure 5.
2. Output Capacitor Selection (COUT)
A. In the majority of applications, low ESR (Equivalent Series
Resistance) electrolytic capacitors between 82 µF and 820 µF and
low ESR solid tantalum capacitors between 10 µF and 470 µF
provide the best results. This capacitor should be located close to
the IC using short capacitor leads and short copper traces. Do not
use capacitors larger than 820 µF.
B. To simplify the capacitor selection procedure, refer to the quick
design component selection table shown in Figure 2. This table
contains different input voltages, output voltages, and load
currents, and lists various inductors and output capacitors that will
provide the best design solutions.
2. Output Capacitor Selection (COUT)
A. See section on output capacitors in application information section.
3. Catch Diode Selection (D1)
A. The catch diode current rating must be at least 1.3 times greater than the
maximum load current. Also, if the power supply design must withstand a
continuous output short, the diode should have a current rating equal to the
maximum current limit of the AP1501. The most stressful condition for
this diode is an overload or shorted output condition.
B. The reverse voltage rating of the diode should be at least 1.25 times the
maximum input voltage.
C. This diode must be fast (short reverse recovery time) and must be
located close to the AP1501 using short leads and short printed circuit
traces. Because of their fast switching speed and low forward voltage drop,
Schottky diodes provide the best performance and efficiency, and should
be the first choice, especially in low output voltage applications.
Ultra-fast recovery, or High-Efficiency rectifiers also provide good results.
Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or
less. Rectifiers such as the 1N5400 series are much too slow and should
not be used.
3. Catch Diode Selection (D1)
A. Refer to the table shown in Figure 11. In this example, a 5A, 20V, 1N5823
Schottky diode will provide the best performance, and will not be overstressed even
for a shorted output.
B. From the inductor value selection guide shown in Figure 5, the
inductance region intersected by the 12V horizontal line and the 3A
vertical line is 33 µH, and the inductor code is L40.
C. The inductance value required is 33 µH. From the table in Figure 8, go to the
L40 line and choose an inductor part number from any of the four manufacturers
shown. (In most in-stance, both through hole and surface mount inductors are
available.)
B. From the quick design component selection table shown in Figure 2, locate the
5V output voltage section. In the load current column, choose the load current line
that is closest to the current needed in your application, for this example, use the 3A
line. In the maximum input voltage column, select the line that covers the input
voltage needed in your application, in this example, use the 15V line. Continuing
on this line are recommended inductors and capacitors that will provide the best
overall performance.
The capacitor list contains both through hole electrolytic and surface mount
tantalum capacitors from four different capacitor manufacturers. It is recommended
that both the manufacturers and the manufacturer’s series that are listed in the table
be used.
In this example aluminum electrolytic capacitors from several different
manufacturers are available with the range of ESR numbers needed.
330 µF 35V Panasonic HFQ Series
330 µF 35V Nichicon PL Series
C. The capacitor voltage rating for electrolytic capacitors should be C. For a 5V output, a capacitor voltage rating at least 7.5V or more is needed. But
even a low ESR, switching grade, 220µF 10V aluminum electrolytic capacitor
at least 1.5 times greater than the output voltage, and often much
would exhibit approximately 225 mW of ESR (see the curve in Figure 14 for the
higher voltage ratings are needed to satisfy the low ESR
ESR vs voltage rating). This amount of ESR would result in relatively high output
requirements for low output ripple voltage.
ripple voltage. To reduce the ripple to 1% of the output voltage, or less, a capacitor
with a higher value or with a higher voltage rating (lower ESR) should be selected.
A 16V or 25V capacitor will reduce the ripple volt-age by approximately half.
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PROCEDURE (Fixed Output Voltage Version)
4. Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed between the
input pin and ground pin to prevent large volt-age transients from
appearing at the input. This capacitor should be located close to the IC
using short leads. In addition, the RMS current rating of the input capacitor
should be selected to be at least 1/2 the DC load current. The capacitor
manufacturers data sheet must be checked to assure that this current rating
is not exceeded. The curve shown in Figure 9 shows typical RMS current
ratings for several different aluminum electrolytic capacitor values.
For an aluminum electrolytic, the capacitor voltage rating should be
approximately 1.5 times the maximum input voltage.
The tantalum capacitor voltage rating should be 2 times the maximum
input voltage and it is recommended that they be surge current tested by
the manufacturer.
Use caution when using ceramic capacitors for input bypassing, because it
may cause severe ringing at the VIN pin.
EXAMPLE (Fixed Output Voltage Version)
4. Input Capacitor (CIN)
The important parameters for the Input capacitor are the input voltage rating and the
RMS current rating. With a nominal
input voltage of 12V, an aluminum electrolytic capacitor with a voltage rating
greater than 18V (1.5 x VIN ) would be needed. The next higher capacitor voltage
rating is 25V.
The RMS current rating requirement for the input capacitor in
a buck regulator is approximately 1 /2 the DC load current. In this example, with a
3A load, a capacitor with a RMS current rating of at least 1.5A is needed. The
curves shown in Figure 9 can be used to select an appropriate input capacitor.
From the curves, locate the 35V line and note which capacitor values have RMS
current ratings greater than 1.5A. A 680µF/35V capacitor could be used.
For a through hole design, a 680µF/35V electrolytic capacitor (Panasonic HFQ
series or Nichicon PL series or equivalent) would be adequate. other types or other
manufacturers capacitors can be used provided the RMS ripple current ratings are
adequate.
For surface mount designs, solid tantalum capacitors can be used, but caution must
be exercised with regard to the capacitor surge current rating. The TPS series
available from AVX, and the 593D series from Sprague are both surge current
tested.
AP1501 SERIES BUCK REGULATOR DESIGN PROCEDURE (FIXED OUTPUT) (Continued)
Conditions
Output
Voltage
(V)
3.3
Load
Current
(A)
3
2
5
3
2
12
3
2
Output Capacitor
Through Hole Electrolytic
Surface Mount Tantalum
Panasonic
AVX TPS
Inductance
Inductor
Max Input
Nichicon PL
Sprague 595D Series
HFQ Series
Series
Voltage (V)
(µ
µH)
(#)
Series (µ
µF/V)
(µ
µF/V)
(µ
µF/V)
(µ
µF/V)
5
22
L41
470/25
560/16
330/6.3
390/6.3
7
22
L41
560/35
560/35
330/6.3
390/6.3
10
22
L41
680/35
680/35
330/6.3
390/6.3
40
33
L40
560/35
470/35
330/6.3
390/6.3
6
22
L33
470/25
470/35
330/6.3
390/6.3
10
33
L32
330/35
330/35
330/6.3
390/6.3
40
47
L39
330/35
270/50
220/10
330/10
8
22
L41
470/25
560/16
220/10
330/10
10
22
L41
560/25
560/25
220/10
330/10
15
33
L40
330/35
330/35
220/10
330/10
40
47
L39
330/35
270/35
220/10
330/10
9
22
L33
470/25
560/16
220/10
330/10
20
68
L38
180/35
180/35
100/10
270/10
40
68
L38
180/35
180/35
100/10
270/10
15
22
L41
470/25
470/25
100/16
180/16
18
33
L40
330/25
330/25
100/16
180/16
30
68
L44
180/25
180/25
100/16
120/20
40
68
L44
180/35
180/35
100/16
120/20
15
33
L32
330/25
330/25
100/16
180/16
20
68
L38
180/25
180/25
100/16
120/20
40
150
L42
82/25
82/25
68/20
68/25
Figure 2. AP1501 Fixed Voltage Quick Design Component Selection Table
Inductor
AP1501 SERIES BUCK REGULATOR DESIGN PROCEDURE (ADJUSTABLE OUTPUT)
PROCEDURE (Adjustable Output Voltage Version)
Given:
VOUT = Regulated Output Voltage
VIN(max) = Maximum Input Voltage
ILOAD(max) = Maximum Load Current
F=Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R1 and R2, as shown in
Figure 1)
Use the following formula to select the appropriate resistor values.
VOUT = VREF (1 +
R2
)
R1
where
VREF = 1.23 V
Select a value for R1 between 240Ω and 1.5kΩ. The lower resistor
values minimize noise pickup in the sensitive feedback pin. (For the
lowest temperature coefficient and the best stability with time, use 1%
metal film resistors.)
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EXAMPLE (Adjustable Output Voltage Version)
Given:
VOUT = 20V
VIN(max) = 28V
ILOAD(max) = 3A
F=Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R1 and R2, as shown
in Figure 1)
Select R1 to be 1 kΩ, 1%. Solve for R2.
R 2 = R 1(
VOUT
20 V
− 1) = 1 k(
− 1)
VREF
1.23 V
R2=1k (16.26-1)=15.26k, closest 1% value is 15.4kΩ
R2 = 15.4 kΩ.
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UMW
R
UMW AP1501
PROCEDURE (Adjustable Output Voltage Version)
R 2 = R 1(
EXAMPLE (Adjustable Output Voltage Version)
VOUT
− 1)
VREF
2. Inductor Selection (L1)
2. Inductor Selection (L1)
A. Calculate the inductor Volt • microsecond constant E•T (V•µs), from A. Calculate the inductor Volt • microsecond constant
the following formula:
(E•T),
E• T = (VIN− VOUT− VSAT) •
VOUT+ VD
1000
•
(V• µ s)
VIN− VSAT+ VD 150kHz
E• T = (28− 20−1.16) •
20+ 0.5
1000
•
(V• µ s)
28−1.16+ 0.5 150
20.5
• 6.67(V • µs) = 34.2(V • µs)
27.34
where VSAT = internal switch saturation voltage = 1.16V
and VD = diode forward voltage drop = 0.5V
E • T = ( 6.84 ) •
B. Use the E•T value from the previous formula and match it with the
E•T number on the vertical axis of the Inductor Value Selection Guide
shown in Figure 7.
C. on the horizontal axis, select the maximum load current.
B. E•T=34.2 (V•µs)
D. Identify the inductance region intersected by the E•T value and the
Maximum Load Current value. Each region is identified by an
inductance value and an inductor code (LXX).
E. Select an appropriate inductor from the four manufacturer’s part
numbers listed in Figure 8.
D. From the inductor value selection guide shown in Figure 7, the
inductance region intersected by the 34 (V•µs) horizontal line and
the 3A vertical line is 47 µH, and the inductor code is L39.
E. From the table in Figure 8, locate line L39, and select an
inductor part number from the list of manufacturers part numbers.
3. Output Capacitor Selection (COUT)
A. In the majority of applications, low ESR electrolytic or solid tantalum
capacitors between 82 µF and 820 µF provide the best results. This capacitor
should be located close to the IC using short capacitor leads and short copper
traces. Do not use capacitors larger than 820 µF.
B. To simplify the capacitor selection procedure, refer to the quick
design table shown in Figure 3. This table contains different output
voltages, and lists various output capacitors that will provide the best
design solutions.
3. Output Capacitor SeIection (COUT)
C. ILOAD (max) = 3A
B. From the quick design table shown in Figure 3, locate the output
voltage column. From that column, locate the output voltage closest to the
output voltage in your application. In this example, select the 24V line.
Under the output capacitor section, select a capacitor from the list of
through hole electrolytic or surface mount tantalum types from four
different capacitor manufacturers. It is recommended that both the
manufacturers and the manufacturers series that are listed in the table be
used.
In this example, through hole aluminum electrolytic capacitors from
several different manufacturers are available.
220 µF/35V Panasonic HFQ Series
150 µF/35V Nichicon PL Series
C. The capacitor voltage rating should be at least 1.5 times greater than C. For a 20V output, a capacitor rating of at least 30V or more is
the output voltage, and often much higher voltage ratings are needed to needed. In this example, either a 35V or 50V capacitor would
satisfy the low ESR requirements needed for low output ripple voltage. work. A 35V rating was chosen, although a 50V rating could also
be used if a lower output ripple voltage is needed.
Other manufacturers or other types of capacitors may also be used,
provided the capacitor specifications (especially the 100 kHz
ESR) closely match the types listed in the table. Refer to the
capacitor manufacturers data sheet for this information.
4. Feedforward Capacitor (CFF ) (See Figure 1)
For output voltages greater than approximately 10V, an additional
capacitor is required. The compensation capacitor is typically between
100 pF and 33 nF, and is wired in parallel with the output voltage
setting resistor, R2. It provides additional stability for high output
voltages, low input-output voltages, and/or very low ESR output
capacitors, such as solid tantalum capacitors.
C FF
= 31 × 101 × R
3
4. Feedforward Capacitor (CFF )
The table shown in Figure 3 contains feed forward capacitor
values for various output voltages. In this example, a 560 pF
capacitor is needed.
2
This capacitor type can be ceramic, plastic, silver mica, etc. (Because of
the unstable characteristics of ceramic capacitors made with Z5U
material, they are not recommended.)
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UMW
R
UMW AP1501
AP1501 SERIES BUCK REGULATOR DESING PROCEDURE (ADJUSTABLE OUTPUT)
Output
Voltage (V)
2
4
6
9
12
15
24
28
Through Hole Output Capacitor
Surface Mount Output Capacitor
AVX TPS Series
Sprague 595D
Panasonic HFQ Nichicon PL Series
Feedforward
Feedforward
Series
Series
(µ
µF/V)
(µ
µF/V)
Capacitor
capacitor
(µ
µF/V)
(µ
µF/V)
820/35
820/35
33 nF
330/6.3
470/4
33 nF
560/35
470/35
10 nF
330/6.3
390/6.3
10 nF
470/25
470/25
3.3 nF
220/10
330/10
3.3 nF
330/25
330/25
1.5 nF
100/16
180/16
1.5 nF
330/25
330/25
1 nF
100/16
180/16
1 nF
220/35
220/35
680 pF
68/20
120/20
680 pF
220/35
150/35
560 pF
33/25
33/25
220 pF
100/50
100/50
390 pF
10/35
15/50
220 pF
Figure 3. Output Capacitor and Feedforward Capacitor Selection Table
40V L29
20V
15V
10V
8V
7V
L30
L21
L40
L31
µH
68
µH
47
L22
L32
L33
µH
33
µH
22
L23
6V
MAXIMUM INPUT VOLTAGE (V)
MAXIMUM INPUT VOLTAGE (V)
AP1501 SERIES BUCK REGULATOR DESIGN PROCEDURE
Inductor Value Selection Guides (For Continuous Mode Operation)
L34
L24
L15
L25
µH
15
L16
5V
1.5 2.0 2.5 3.0
0.6 0.8 1.0
MAXIMUM LOAD CURRENT (A)
Figure 4. AP1501-3.3
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40V L27
30V
H
0µ
15
25V
L37
H
0µ
10
L28
20V
19V L29
18V
17V
16V L21
15V
L43
L36
L38
L39
L30
µH
68
L22
L40
L31
µH
47
L32
H
33µ
L33
µH
22
L23
L24
15
µH
L34
14V
1.5 2.0 2.5 3.0
0.6 0.8 1.0
MAXIMUM LOAD CURRENT (A)
Figure 6. AP1501-12
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UMW AP1501
40V
20V
15V
L29
L30
H
0µ
10
µH
68
12V
L21
10V
9V
L38
L31
47
µH
L40
L32
L22
33
8V
L39
E•T(V•µs)
MAXIMUM INPUT VOLTAGE (V)
UMW
R
L33
µH
L23
2
L24
1
25
H
5µ
L25
7V
1.5 2.0 2.5 3.0
0.6 0.8 1.0
MAXIMUM LOAD CURRENT (A)
Figure 5. AP1501-5.0
µH
100
20
15
10
9
8
7
6
5
4
L34
H
2µ
Figure 7. AP1501-ADJ
70
L35
60 L27
L43
50 220µH
L36
L44
L28
L37
40
H
µ
0
15
L29
L38
30
L21
H
68µ
L30
47µ
H
L31
H
33µ
L22
L32
L39
L40
L33
H
22µ
L23
L34
L24
L15
H
15µ
L25
1.5 2.0 2.5 3.0
0.6 0.8 1.0
MAXIMUM LOAD CURRENT (A)
AP1501 SERIES BUCK REGULATOR DESIGN PROCEDURE (Continued)
Inductance
(µ
µH)
L15
L21
L22
L23
L24
L25
L26
L27
L28
L29
L30
L31
L32
L33
L34
L35
L36
L37
L38
L39
L40
L41
L42
L43
L44
22
68
47
33
22
15
330
220
150
100
68
47
33
22
15
220
150
100
68
47
33
22
150
100
68
Current
(A)
0.99
0.99
1.17
1.40
1.70
2.10
0.80
1.00
1.20
1.47
1.78
2.20
2.50
3.10
3.40
1.70
2.10
2.50
3.10
3.50
3.50
3.50
2.70
3.40
3.40
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
Schott
Renco
Pulse Engineering
Through
Surface
Through Hole
Surface
Through
Surface
Hole
Mount
Mount
Hole
Mount
67148350 67148460
RL-1284-22-43
RL1500-22 PE-53815
PE-53815-S
67144070 67144450
RL-5471-5
RL1500-68 PE-53821
PE-53821-S
67144080 67144460
RL-5471-6
PE-53822
PE-53822-S
67144090 67144470
RL-5471-7
PE-53823
PE-53823-S
67148370 67148480
RL-1283-22-43
PE-53824
PE-53825-S
67148380 67148490
RL-1283-15-43
PE-53825
PE-53824-S
67144100 67144480
RL-5471-1
PE-53826
PE-53826-S
67144110 67144490
RL-5471-2
PE-53827
PE-53827-S
67144120 67144500
RL-5471-3
PE-53828
PE-53828-S
67144130 67144510
RL-5471-4
PE-53829
PE-53829-S
67144140 67144520
RL-5471-5
PE-53830
PE-53830-S
67144150 67144530
RL-5471-6
PE-53831
PE-53831-S
67144160 67144540
RL-5471-7
PE-53932
PE-53932-S
67148390 67148500
RL-1283-22-43
PE-53933
PE-53933-S
67148400 67148790
RL-1283-15-43
PE-53934
PE-53934-S
67144170
RL-5473-1
PE-53935
PE-53935-S
67144180
RL-5473-4
PE-54036
PE-54036-S
67144190
RL-5472-1
PE-54037
PE-54037-S
67144200
RL-5472-2
PE-54038
PE-54038-S
67144210
RL-5472-3
PE-54039
PE-54039-S
67144220 67148290
RL-5472-4
PE-54040
PE-54040-S
67144230 67148300
RL-5472-5
PE-54041
PE-54041-S
67148410
RL-5473-4
PE-54042
PE-54042-S
67144240
RL-5473-2
PE-54043
67144250
RL-5473-3
PE-54044
Figure 8. Inductor Manufacturers Part Numbers
Coilcraft
Surface Mount
DO3308-223
DO3316-683
DO3316-473
DO3316-333
DO3316-223
DO3316-153
DO5022P-334
DO5022P-224
DO5022P-154
DO5022P-104
DO5022P-683
DO5022P-473
DO5022P-333
DO5022P-223
DO5022P-153
-
Figure 9. RMS Current Ratings for Low ESR
Electrolytic Capacitors (typical)
0 10 20 30 40 50 60 70
CAPACITOR VOLTAGE RATING (V) 1
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