AP6502 [DIODES]

340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER; 340kHz 23V 2A同步DC / DC降压转换器
AP6502
型号: AP6502
厂家: DIODES INCORPORATED    DIODES INCORPORATED
描述:

340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER
340kHz 23V 2A同步DC / DC降压转换器

转换器
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中文:  中文翻译
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AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Description  
Pin Assignments  
The AP6502 is a 340kHz switching frequency external  
compensated synchronous DCDC buck converter. It has  
integrated low RDSON high and low side MOSFETs.  
( Top View )  
The AP6502 enables continues load current of up to 2A with  
efficiency as high as 95%.  
BS  
IN  
1
2
8
7
SS  
EN  
The AP6502 features current mode control operation, which  
enables fast transient response times and easy loop  
stabilization.  
3
4
6
5
COMP  
FB  
SW  
The AP6502 simplifies board layout and reduces space  
requirements with its high level of integration and minimal  
need for external components, making it ideal for distributed  
power architectures.  
GND  
SO-8EP  
The AP6502 is available in a standard Green SO-8EP  
package with exposed PAD for improved thermal  
performance and is RoHS compliant.  
Figure 1. Package Pin Out  
Features  
Applications  
VIN 4.75V to 23V  
Gaming Consoles  
Flat Screen TV sets and Monitors  
Set Top Boxes  
2A continuous Output Current, 3A Peak  
VOUT adjustable to 0.925 to 20V  
Distributed power systems  
Home Audio  
340kHz switching frequency  
Programmable Soft-Start  
Enable pin  
Consumer electronics  
Network Systems  
Protection  
FPGA, DSP and ASIC Supplies  
Green Electronics  
o
o
OCP  
Thermal Shutdown  
Lead Free Finish/ RoHS Compliant (Note 1)  
Note:  
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.  
Typical Application Circuit  
100  
90  
V
= 5V  
IN  
V
= 12V  
IN  
80  
70  
60  
50  
V
= 3.3V  
OUT  
L = 10µH  
40  
0
0.4  
0.8  
1.2  
1.6  
2
LOAD CURRENT (A)  
Efficiency vs. Load Current  
Figure 2. Typical Application Circuit  
1 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Pin Descriptions  
Pin #  
Name  
Description  
High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET  
switch. Connect a 0.01µF or greater capacitor from SW to BS to power the high side switch.  
1
BS  
Power Input. IN supplies the power to the IC, as well as the step-down converter switches.  
Drive IN with a 4.75V to 23V power source. Bypass IN to GND with a suitably large capacitor  
to eliminate noise on the input to the IC. See Input Capacitor.  
2
IN  
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.  
3
4
5
SW  
GND  
FB  
Ground (Connect the exposed pad to Pin 4).  
Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive  
voltage divider connected to it from the output voltage. The feedback threshold is 0.925V. See  
Setting the Output Voltage.  
Compensation Node. COMP is used to compensate the regulation control loop. Connect a  
series RC network from COMP to GND. In some cases, an additional capacitor from COMP to  
GND is required. See Compensation Components.  
6
7
8
COMP  
EN  
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on  
the regulator; low to turn it off. Attach to IN with a 100kpull up resistor for automatic startup.  
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to GND  
to set the soft-start period. A 0.1µF capacitor sets the soft-start period to 15ms. To disable the  
soft-start feature, leave SS floating.  
SS  
Functional Block Diagram  
Figure 3. Functional Block Diagram  
+
-
IN  
2
OVP  
CURRENT  
SENSE  
AMPLIFIER  
+
RAMP  
1.1V  
OSCILLATOR  
E
-
+
-
5
FB  
100/340 KHz  
CLK  
BS  
1
Logic  
0.3 V  
100m  
+
-
SW  
3
SS  
-
8
6
+
+
CURRENT  
COMPARATOR  
100mꢀ  
ERROR  
AMPLIFIER  
6uA  
0.923 V  
GND  
4
COMP  
+
-
2.5V  
EN OK  
disable  
LOCKOUT  
COMPARATOR  
IN < 4.10V  
IN  
EN  
+
-
7
INTERNAL  
REGULATORS  
5V  
SHUTDOWN  
COMPARATOR  
0.9V  
2 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Absolute Maximum Ratings (Note 2)  
Symbol  
VIN  
Parameter  
Rating  
-0.3 to 26  
Unit  
V
Supply Voltage  
VSW  
VBS  
Switch Node Voltage  
Bootstrap Voltage  
Feedback Voltage  
Enable/UVLO Voltage  
Comp Voltage  
-1.0 to VIN+0.3  
VSW-0.3 to VSW + 6  
–0.3V to +6  
–0.3V to +6  
–0.3V to +6  
-65 to +150  
+150  
V
V
VFB  
V
VEN  
VCOMP  
TST  
V
V
Storage Temperature  
Junction Temperature  
Lead Temperature  
°C  
°C  
°C  
TJ  
TL  
+260  
ESD Susceptibility (Note 3)  
HBM  
MM  
Human Body Model  
4
400  
1
kV  
V
Machine Model  
CDM  
Charged Device Model  
kV  
Notes:  
only;  
2. Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings  
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.  
3. 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 4)  
Symbol  
θJA  
Parameter  
Junction to Ambient  
Junction to Case  
Rating  
74  
Unit  
°C/W  
°C/W  
θJC  
16  
Note: 4. Test condition for SO-8EP: Measured on approximately 1” square of 1 oz copper  
Recommended Operating Conditions (Note 5)  
Symbol  
VIN  
Parameter  
Min  
4.75  
-40  
Max  
23  
Unit  
V
Supply Voltage  
Operating Ambient Temperature Range  
TA  
+85  
°C  
Note: 5. The device function is not guaranteed outside of the recommended operating conditions.  
3 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Electrical Characteristics (VIN = 12V, TA = +25°C, unless otherwise noted)  
Symbol  
Parameter  
Shutdown Supply Current  
Supply Current (Quiescent)  
Test Conditions  
VEN = 0V  
Min  
Typ.  
0.3  
Max  
3.0  
Unit  
µA  
IIN  
IIN  
VEN = 2.0V, VFB = 1.0V  
0.6  
1.5  
mA  
High-Side Switch On-Resistance  
(Note 6)  
RDS(ON)1  
RDS(ON)2  
100  
100  
mꢀ  
mꢀ  
Low-Side Switch On-Resistance  
(Note 6)  
ILimit  
ILimit  
HS Current Limit  
LS Current Limit  
Minimum duty cycle  
From Drain to Source  
4.4  
0.9  
A
A
VEN = 0V, VSW = 0V,  
Vsw=12V  
High-Side Switch Leakage Current  
0
10  
μA  
AVEA  
GEA  
Error Amplifier Voltage Gain (Note 5)  
Error Amplifier Transconductance  
800  
V/V  
ΔIC = ±10μA  
1000  
uA/V  
COMP to Current Sense  
Transconductance  
GCS  
2.8  
A/V  
FSW  
FFB  
Oscillator Frequency  
VFB = 0.75V  
VFB = 0V  
300  
900  
340  
0.30  
90  
380  
950  
kHz  
fSW  
%
Fold-back Frequency  
DMAX  
TON  
VFB  
Maximum Duty Cycle  
VFB = 800mV  
Minimum On Time  
200  
925  
1.1  
ns  
mV  
V
Feedback Voltage  
TA = -40°C to +85°C  
Feedback Overvoltage Threshold  
EN Rising Threshold  
VEN_Rising  
0.7  
2.2  
0.8  
0.9  
2.7  
V
EN Lockout Threshold Voltage  
EN Lockout Hysteresis  
VIN Under Voltage Threshold Rising  
2.5  
V
220  
4.05  
mV  
V
INUVVth  
3.80  
4.40  
VIN Under Voltage Threshold  
Hysteresis  
INUVHYS  
250  
mV  
Soft-Start Current  
Soft-Start Period  
Thermal Shutdown  
VSS = 0V  
6
μA  
ms  
°C  
CSS = 0.1µF  
15  
TSD  
150  
Note: 6. Guaranteed by design  
4 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Typical Performance Graphs (VIN = 12V, VOUT=3.3V ,TA = +25°C, unless otherwise noted)  
0.6  
0.074  
6.2  
6
0.064  
0.054  
0.044  
0.034  
0.58  
0.56  
5.8  
5.6  
0.54  
0.52  
5.4  
5.2  
0.024  
0.014  
0.5  
5
4.8  
0.004  
0.48  
0
5
10  
INPUT VOLTAGE (V)  
Shutdown Supply Current vs. Input Voltage  
15  
20  
25  
-60 -40 -20  
0
20  
TEMPERATURE (C)  
Current Limit vs. Temperature  
40  
60  
80 100  
0
5
10  
INPUT VOLTAGE (V)  
Quiescent Supply Current vs. Input Voltage  
15  
20  
25  
3.33  
0.92  
0.918  
0.916  
0.914  
0.912  
375  
370  
365  
3.329  
3.328  
3.327  
3.326  
3.325  
3.324  
0.91  
360  
355  
350  
0.908  
3.323  
3.322  
0.906  
0.904  
3.321  
3.32  
0.902  
0.9  
-60 -40  
-20  
0
20  
TEMPERATURE (°C)  
Oscillator Frequency vs. Temperature  
40  
60  
80 100  
4.75  
9.75  
14.75  
INPUT VOLTAGE (V)  
Line Regulation  
19.75  
24.75  
-60 -40  
-20  
0
20  
TEMPERATURE (°C)  
Feedback Voltage vs. Temperature  
40  
60  
80 100  
90  
85  
80  
90  
85  
80  
100  
90  
80  
70  
75  
70  
65  
60  
V
= 5V  
75  
70  
65  
IN  
V = 12V  
IN  
V
= 5V  
IN  
V
= 12V  
IN  
60  
60  
50  
55  
50  
45  
55  
50  
45  
V
= 1.2V  
V
V
= 12V  
OUT  
L = 3.3µH  
IN  
V
= 1.8V  
OUT  
L = 3.3µH  
= 5V  
OUT  
L = 10µH  
40  
40  
40  
0
0.4  
0.8  
1.2  
1.6  
2
0
0.4  
0.8  
1.2  
1.6  
2
0
0.4  
0.8  
LOAD CURRENT (A)  
Efficiency vs. Load Current  
1.2  
1.6  
2
LOAD CURRENT (A)  
Efficiency vs. Load Current  
LOAD CURRENT (A)  
Efficiency vs. Load Current  
5 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Typical Performance Characteristics  
(VIN = 12V, VOUT=3.3V ,L=3.3µH, C1=22uF, C2=47uF, TA = +25°C, unless otherwise noted)  
Steady State Test no load  
Steady State Test 2A  
Startup Through Enable_no load  
Time-10ms/div  
Time-2us/div  
Time-2us/div  
Shutdown Through Enable_no load  
Startup Through Enable 2A  
Shutdown Through Enable 2A  
Time-10ms/div  
Time-5ms/div  
Time-2ms/div  
Load Transient Test 1.0A to 2.0A  
Short Circuit Test  
Short Circuit Recovery  
Time-20us/div  
Time-100us/div  
Time-20us/div  
6 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Applications Information  
Theory of Operation  
External Soft Start  
The AP6502 is a 2A current mode control, synchronous  
buck regulator with built in power MOSFETs. Current  
mode control assures excellent line and load regulation  
and a wide loop bandwidth for fast response to load  
transients.  
Soft start is traditionally implemented to prevent the  
excess inrush current. This in turn prevents the  
converter output voltage from overshooting when it  
reaches regulation. The AP6502 has an internal current  
source with a soft start capacitor to ramp the reference  
voltage from 0V to 0.925V. The soft start current is 6uA.  
The soft start sequence is reset when there is a Thermal  
Shutdown, Under Voltage Lockout (UVLO) or when the  
part is disabled using the EN pin.  
Figure 3 depicts the functional block diagram of AP6502.  
The operation of one switching cycle can be explained as  
follows. At the beginning of each cycle, HS (high-side)  
MOSFET is off. The EA output voltage is higher than the  
current sense amplifier output, and the current  
comparator’s output is low. The rising edge of the 340kHz  
oscillator clock signal sets the RS Flip-Flop. Its output  
turns on HS MOSFET. The current sense amplifier is reset  
for every switching cycle.  
External Soft Start can be calculated from the formula  
below:  
DV  
I
= C *  
SS  
DT  
When the HS MOSFET is on, inductor current starts to  
increase. The Current Sense Amplifier senses and  
amplifies the inductor current. Since the current mode  
control is subject to sub-harmonic oscillations that peak at  
half the switching frequency, Ramp slope compensation is  
utilized. This will help to stabilize the power supply. This  
Ramp compensation is summed to the Current Sense  
Amplifier output and compared to the Error Amplifier  
output by the PWM Comparator. When the sum of the  
Current Sense Amplifier output and the Slope  
Compensation signal exceeds the EA output voltage, the  
RS Flip-Flop is reset and HS MOSFET is turned off.  
Where;  
Iss = Soft Start Current  
C = External Capacitor  
DV=change in feedback voltage from 0V to maximum  
voltage  
DT = Soft Start Time  
Current Limit Protection  
In order to reduce the total power dissipation and to  
protect the application, AP6502 has cycle-by-cycle  
current limiting implementation. The voltage drop across  
the internal high-side MOSFET is sensed and compared  
with the internally set current limit threshold. This voltage  
drop is sensed at about 30ns after the HS turns on.  
When the peak inductor current exceeds the set current  
limit threshold, current limit protection is activated.  
During this time the feedback voltage (VFB) drops down.  
When the voltage at the FB pin reaches 0.3V, the internal  
oscillator shifts the frequency from the normal operating  
frequency of 340Khz to a fold-back frequency of 102Khz.  
The current limit is reduced to 70% of nominal current  
limit when the part is operating at 102Khz. This low Fold-  
back frequency prevents runaway current.  
For one whole cycle, if the sum of the Current Sense  
Amplifier output and the Slope Compensation signal does  
not exceed the EA output, then the falling edge of the  
oscillator clock resets the Flip-Flop. The output of the Error  
Amplifier increases when feedback voltage (VFB) is lower  
than the reference voltage of 0.925V. This also increases  
the inductor current as it is proportional to the EA voltage.  
If in one cycle the current in the power MOSFET does not  
reach the COMP set current value, the power MOSFET  
will be forced to turn off. When the HS MOSFET turns off,  
the synchronous LS MOSFET turns on until the next clock  
cycle begins. There is a “dead time” between the HS turn  
off and LS turn on that prevents the switches from  
“shooting through” from the input supply to ground.  
Under Voltage Lockout (UVLO)  
Under Voltage Lockout is implemented to prevent the IC  
from insufficient input voltages. The AP6502 has a  
UVLO comparator that monitors the input voltage and the  
internal bandgap reference. If the input voltage falls  
below 4.0V, the AP6502 will latch an under voltage fault.  
In this event the output will be pulled low and power has  
to be re-cycled to reset the UVLO fault.  
The voltage loop is compensated through an internal  
transconductance amplifier and can be adjusted through  
the external compensation components.  
Enable  
The enable (EN) input allows the user to control turning on  
or off the regulator. To enable the regulator EN must be  
pulled above the ‘EN Rising Threshold’ and to disable the  
regulator EN must be pulled below ‘EN falling Threshold’  
(EN rising threshold – En threshold Hysteresis).  
Over Voltage Protection  
When the AP6502 FB pin exceeds 20% of the nominal  
regulation voltage of 0.925V, the over voltage comparator  
is tripped and the COMP pin and the SS pin are  
discharged to GND, forcing the high-side switch off.  
7 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Applications Information (cont.)  
Thermal Shutdown  
Compensation Components  
The AP6502 has on-chip thermal protection that prevents  
damage to the IC when the die temperature exceeds safe  
margins. It implements a thermal sensing to monitor the  
operating junction temperature of the IC. Once the die  
temperature rises to approximately 150°C, the thermal  
protection feature gets activated .The internal thermal  
sense circuitry turns the IC off thus preventing the power  
switch from damage.  
The AP6502 has an external COMP pin through which  
system stability and transient response can be controlled.  
COMP pin is the output of the internal trans-conductance  
error amplifier. A series capacitor-resistor combination  
sets  
a
pole-zero combination to control the  
characteristics of the control system. The DC gain of the  
voltage feedback loop is given by:  
A hysteresis in the thermal sense circuit allows the device  
to cool down to approximately 120°C before the IC is  
enabled again through soft start. This thermal hysteresis  
feature prevents undesirable oscillations of the thermal  
protection circuit.  
V
FB  
A
= R  
LOAD  
×G  
CS  
× A  
×
VEA  
VDC  
V
OUT  
Where VFB is the feedback voltage (0.925V), RLOAD is the  
load resistor value, GCS is the current sense trans-  
conductance and AVEA is the error amplifier voltage gain.  
The control loop transfer function incorporates two poles  
one is due to the compensation capacitor (C3) and the  
output resistor of error amplifier, and the other is due to  
the output capacitor and the load resistor. These poles  
are located at:  
Setting the Output Voltage  
The output voltage can be adjusted from 0.925V to 18V  
using an external resistor divider. Table 1 shows a list of  
resistor selection for common output voltages. Resistor  
R1 is selected based on a design tradeoff between  
efficiency and output voltage accuracy. For high values of  
R1 there is less current consumption in the feedback  
network. However the trade off is output voltage accuracy  
due to the bias current in the error amplifier. R2 can be  
determined by the following equation:  
G
EA  
f
=
P1  
2π×C3× A  
VEA  
1
V
f
=
OUT  
P2  
R
1
= R ⋅ ⎜  
1⎟  
2
2π × C2×R  
LOAD  
0.925  
Where GEA is the error amplifier trans-conductance.  
One zero is present due to the compensation capacitor  
(C3) and the compensation resistor (R3). This zero is  
located at:  
1
f
=
Z1  
2π×C3×R3  
Figure 4. Feedback Divider Network  
The goal of compensation design is to shape the  
converter transfer function to get a desired loop gain. The  
system crossover frequency where the feedback loop  
has the unity gain is crucial.  
When output voltage is low, network as shown in Figure 4  
is recommended.  
A rule of thumb is to set the crossover frequency to below  
one-tenth of the switching frequency. Use the following  
procedure to optimize the compensation components:  
Vout(V)  
5
3.3  
2.5  
1.8  
R1(K)  
45.3  
26.1  
16.9  
9.53  
3
R2(K)  
10  
10  
10  
10  
10  
1. Choose the compensation resistor (R3) to set the  
desired crossover frequency. Determine the R3 value by  
the following equation:  
1.2  
Table 1—Resistor Selection for Common Output  
Voltages  
V
V
OUT  
2π × C2× fc  
2π × C2× 0.1× fs  
OUT  
R3 =  
×
<
×
×G  
G
× G  
V
G
V
CS  
EA  
CS  
FB  
FB  
EA  
Where fC is the crossover frequency, which is typically  
less than one tenth of the switching frequency.  
10 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Applications Information (cont.)  
Input Capacitor  
Compensation Components (cont.)  
The input capacitor reduces the surge current drawn from  
the input supply and the switching noise from the device.  
The input capacitor has to sustain the ripple current  
produced during the on time on the upper MOSFET. It  
must hence have a low ESR to minimize the losses.  
2. Choose the compensation capacitor (C3) to achieve the  
desired phase margin set the compensation zero, fZ1, to  
below one fourth of the crossover frequency to provide  
sufficient phase margin. Determine the C3 value by the  
following equation:  
The RMS current rating of the input capacitor is a critical  
parameter that must be higher than the RMS input  
current. As a rule of thumb, select an input capacitor  
which has RMs rating that is greater than half of the  
maximum load current.  
2
C3 >  
π×R3× fc  
Where R3 is the compensation resistor value.  
Cin/C1  
(µF)  
Cout/C2  
(µF)  
Rc/R3  
(k)  
Cc/C3  
(nF)  
L1  
(µH)  
VOUT  
(V)  
Due to large dI/dt through the input capacitors,  
electrolytic or ceramics should be used. If a tantalum  
must be used, it must be surge protected. Otherwise,  
capacitor failure could occur. For most applications, a  
4.7µF ceramic capacitor is sufficient.  
1.2  
1.8  
2.5  
3.3  
5
22  
22  
22  
22  
22  
22  
47  
47  
47  
47  
47  
47  
3.24  
6.8  
6.8  
6.8  
6.8  
6.8  
6.8  
6.8  
6.8  
6.8  
6.8  
6.8  
3.3  
3.3  
10  
10  
10  
15  
Output Capacitor  
12  
The output capacitor keeps the output voltage ripple  
small, ensures feedback loop stability and reduces the  
overshoot of the output voltage. The output capacitor is a  
basic component for the fast response of the power  
supply. In fact, during load transient, for the first few  
microseconds it supplies the current to the load. The  
converter recognizes the load transient and sets the duty  
cycle to maximum, but the current slope is limited by the  
inductor value.  
Table 2—Resistor  
Component Selection  
Inductor  
Calculating the inductor value is a critical factor in  
designing a buck converter. For most designs, the  
following equation can be used to calculate the inductor  
value;  
V
(V V )  
OUT  
V
IN OUT  
L =  
ΔI f  
L SW  
IN  
Maximum capacitance required can be calculated from  
the following equation:  
ESR of the output capacitor dominates the output voltage  
ripple. The amount of ripple can be calculated from the  
equation below:  
Where ΔIL  
is the inductor ripple current.  
And fSW is the buck converter switching frequency.  
Choose the inductor ripple current to be 30% of the  
maximum load current. The maximum inductor peak  
current is calculated from:  
Vout  
= ΔI * ESR  
inductor  
capacitor  
An output capacitor with ample capacitance and low ESR  
is the best option. For most applications, a 22µF ceramic  
capacitor will be sufficient.  
ΔI  
L
I
= I +  
L(MAX) LOAD  
2
ΔIinductor  
2
L(Iout  
+
)
2
Co =  
Peak current determines the required saturation current  
rating, which influences the size of the inductor. Saturating  
the inductor decreases the converter efficiency while  
increasing the temperatures of the inductor and the  
internal MOSFETs. Hence choosing an inductor with  
appropriate saturation current rating is important.  
2
(Δ V + Vout )2 Vout  
Where ΔV is the maximum output voltage overshoot.  
PC Board Layout  
This is a high switching frequency converter. Hence  
attention must be paid to the switching currents  
interference in the layout. Switching current from one  
power device to another can generate voltage transients  
across the impedances of the interconnecting bond wires  
and circuit traces. These interconnecting impedances  
should be minimized by using wide, short printed circuit  
traces.  
A 1µH to 10µH inductor with a DC current rating of at least  
25% percent higher than the maximum load current is  
recommended for most applications.  
For highest efficiency, the inductor’s DC resistance  
should be less than 200m. Use a larger inductance  
for improved efficiency under light load conditions.  
9 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Applications Information (cont.)  
efficiency of the regulator. This solution is also applicable  
for D > 65%. The bootstrap diode can be a low cost one  
such as BAT54 or a schottky that has a low Vf.  
External  
feedback  
resistor dividers  
must be placed  
close to the FB  
34mm  
Input capacitor C1  
must be placed as  
close as possible  
to the IC and to L1.  
52mm  
Figure 7—External Bootstrap  
Compensation Components  
AP6502 is exposed at the bottom of the package and must  
be soldered directly to a well designed thermal pad on the  
PCB. This will help to increase the power dissipation.  
Recommended Diodes:  
Voltage/Current  
Part Number  
Vendor  
Rating  
30V, 1A  
30V, 1A  
External Bootstrap Diode  
B130  
SK13  
Diodes Inc  
Diodes Inc  
It is recommended that an external bootstrap diode be  
added when the input voltage is no greater than 5V or the  
5V rail is available in the system. This helps to improve the  
Ordering Information  
13” Tape and Reel  
Packaging  
(Note 7)  
Package  
Code  
Device  
Quantity  
Part Number Suffix  
AP6502SP-13  
SP  
SO-8EP  
2500/Tape & Reel  
-13  
Note: 7. 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.  
10 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
Marking Information  
Package Outline Dimensions (All Dimensions in mm)  
Detail "A"  
7°~9°  
Exposed pad  
45°  
1
1
7°~9°  
0.15/0.25  
3.3Ref.  
Bottom View  
0.3/0.5  
1.27typ  
Gauge Plane  
Seating Plane  
4.85/4.95  
0.62/0.82  
1
Detail "A"  
8x-0.60  
Exposed pad  
6x-1.27  
Land Pattem Recommendation  
(Unit:mm)  
11 of 12  
www.diodes.com  
September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  
AP6502  
340kHz 23V 2A SYNCHRONOUS DC/DC BUCK CONVERTER  
IMPORTANT NOTICE  
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS  
DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A  
PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).  
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other  
changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability  
arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any  
license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described  
herein 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 Diodes Incorporated website, harmless against all damages.  
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized  
sales channel.  
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall  
indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees  
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.  
Products described herein may be covered by one or more United States, international or foreign patents pending. Product names  
and markings noted herein may also be covered by one or more United States, international or foreign trademarks.  
LIFE SUPPORT  
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without  
the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:  
A. Life support devices or systems are devices or systems which:  
1. are intended to implant into the body, or  
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided  
in the labeling can be reasonably expected to result in significant injury to the user.  
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected  
to cause the failure of the life support device or to affect its safety or effectiveness.  
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or  
systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements  
concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems,  
notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further,  
Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes  
Incorporated products in such safety-critical, life support devices or systems.  
Copyright © 2011, Diodes Incorporated  
www.diodes.com  
12 of 12  
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September 2011  
© Diodes Incorporated  
AP6502  
Document Number: DS35423 Rev. 2 - 2  

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