LM5000SDX-6/NOPB [NSC]

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LM5000SDX-6/NOPB
型号: LM5000SDX-6/NOPB
厂家: National Semiconductor    National Semiconductor
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稳压器 开关 光电二极管 高压
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February 2007  
LM5000  
High Voltage Switch Mode Regulator  
General Description  
Features  
The LM5000 is a monolithic integrated circuit specifically de-  
signed and optimized for flyback, boost or forward power  
converter applications. The internal power switch is rated for  
a maximum of 80V, with a current limit set to 2A. Protecting  
the power switch are current limit and thermal shutdown cir-  
cuits. The current mode control scheme provides excellent  
rejection of line transients and cycle-by-cycle current limiting.  
An external compensation pin and the built-in slope compen-  
sation allow the user to optimize the frequency compensation.  
Other distinctive features include softstart to reduce stresses  
during start-up and an external shutdown pin for remote ON/  
OFF control. There are two operating frequency ranges avail-  
able. The LM5000-3 is pin selectable for either 300kHz (FS  
Grounded) or 700kHz (FS Open). The LM5000-6 is pin se-  
lectable for either 600kHz (FS Grounded) or 1.3MHz (FS  
Open). The device is available in a low profile 16-lead TSSOP  
package or a thermally enhanced 16-lead LLP package.  
80V internal switch  
Operating input voltage range of 3.1V to 40V  
Pin selectable operating frequency  
300kHz/700kHz (-3)  
600kHz/1.3MHz (-6)  
Adjustable output voltage  
External compensation  
Input undervoltage lockout  
Softstart  
Current limit  
Over temperature protection  
External shutdown  
Small 16-Lead TSSOP or 16-Lead LLP package  
Applications  
Flyback Regulator  
Forward Regulator  
Boost Regulator  
DSL Modems  
Distributed Power Converters  
Typical Application Circuit  
20031901  
LM5000 Flyback Converter  
© 2007 National Semiconductor Corporation  
200319  
www.national.com  
Connection Diagram  
Top View  
20031904  
Ordering Information  
Order Number  
LM5000-3MTC  
LM5000-3MTCX  
LM5000SD-3  
Package Type  
TSSOP-16  
TSSOP-16  
LLP-16  
NSC Package Drawing  
MTC16  
Supplied As  
94 Units, Rail  
MTC16  
2500 Units, Tape and Reel  
1000 Units, Rail  
SDA16  
LM5000SDX-3  
LM5000SD-6  
LLP-16  
SDA16  
4500 Units, Tape and Reel  
1000 Units, Rail  
LLP-16  
SDA16  
LM5000SDX-6  
LLP-16  
SDA16  
4500 Units, Tape and Reel  
Pin Descriptions  
Pin  
Name  
Function  
1
COMP  
Compensation network connection. Connected to the output of the voltage error amplifier. The RC  
compenstion network should be connected from this pin to AGND. An additional 100pF high  
frequency capacitor to AGND is recommended.  
2
3
FB  
Output voltage feedback input.  
SHDN  
AGND  
PGND  
PGND  
PGND  
PGND  
SW  
Shutdown control input, Open = enable, Ground = disable.  
Analog ground, connect directly to PGND.  
4
5
Power ground.  
6
Power ground.  
7
Power ground.  
8
Power ground.  
9
Power switch input. Switch connected between SW pins and PGND pins  
Power switch input. Switch connected between SW pins and PGND pins  
Power switch input. Switch connected between SW pins and PGND pins  
Bypass-Decouple Capacitor Connection, 0.1µF ceramic capacitor recommended.  
Analog power input. A small RC filter is recommended, to suppress line glitches. Typical values of  
10and 0.1µF are recommended.  
10  
11  
12  
13  
SW  
SW  
BYP  
VIN  
14  
15  
16  
-
SS  
FS  
Softstart Input. External capacitor and internal current source sets the softstart time.  
Switching frequency select input. Open = Fhigh. Ground = Flow  
Factory test pin, connect to ground.  
TEST  
Exposed Pad  
underside of LLP  
package  
Connect to system ground plane for reduced thermal resistance.  
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2
Infrared (15 sec.)  
ESD Susceptibility (Note 3)  
Human Body Model  
Machine Model  
235°C  
Absolute Maximum Ratings (Note 1)  
If Military/Aerospace specified devices are required,  
please contact the National Semiconductor Sales Office/  
Distributors for availability and specifications.  
2kV  
200V  
Storage Temperature  
−65°C to +150°C  
VIN  
-0.3V to 40V  
-0.3V to 80V  
-0.3V to 5V  
-0.3V to 3V  
-0.3V to 7V  
150°C  
SW Voltage  
FB Voltage  
Operating Conditions  
Operating Junction  
Temperature Range  
(Note 7)  
COMP Voltage  
All Other Pins  
Maximum Junction Temperature  
Power Dissipation(Note 2)  
Lead Temperature  
−40°C to +125°C  
3.1V to 40V  
Supply Voltage (Note 7)  
Internally Limited  
216°C  
Electrical Characteristics  
Specifications in standard type face are for TJ = 25°C and those with boldface type apply over the full Operating Temperature  
Range (TJ = −40°C to +125°C) Unless otherwise specified. VIN = 12V and IL = 0A, unless otherwise specified.  
Min  
(Note 4)  
Typ  
(Note 5)  
Max  
(Note 4)  
Symbol  
Parameter  
Conditions  
Units  
mA  
IQ  
Quiescent Current  
FB = 2V (Not Switching)  
FS = 0V  
2.0  
2.1  
2.5  
2.5  
FB = 2V (Not Switching)  
FS = Open  
mA  
VSHDN = 0V  
18  
30  
1.2840  
2.7  
µA  
V
VFB  
Feedback Voltage  
1.2330  
1.35  
1.259  
2.0  
ICL  
Switch Current Limit  
A
Feedback Voltage Line  
Regulation  
0.001  
0.04  
%/V  
%VFBVIN  
3.1V VIN 40V  
IB  
FB Pin Bias Current (Note 6)  
55  
200  
nA  
V
BV  
Output Switch Breakdown  
Voltage  
TJ = 25°C, ISW = 0.1µA  
80  
TJ = -40°C to + 125°C, ISW  
0.5µA  
=
76  
VIN  
gm  
Input Voltage Range  
3.1  
40  
V
µmho  
V/V  
%
Error Amp Transconductance  
Error Amp Voltage Gain  
150  
410  
280  
90  
750  
ΔI = 5µA  
AV  
DMAX  
Maximum Duty Cycle  
LM5000-3  
FS = 0V  
FS = 0V  
85  
85  
Maximum Duty Cycle  
LM5000-6  
90  
%
TMIN  
fS  
Minimum On Time  
165  
300  
700  
600  
1.3  
ns  
Switching Frequency  
LM5000-3  
FS = 0V  
240  
550  
360  
840  
715  
1.545  
-2  
kHz  
FS = Open  
FS = 0V  
Switching Frequency  
LM5000-6  
485  
FS = Open  
VSHDN = 0V  
VSW = 80V  
ISW = 1A  
1.055  
MHz  
µA  
ISHDN  
IL  
Shutdown Pin Current  
Switch Leakage Current  
Switch RDSON  
−1  
0.008  
160  
0.6  
5
µA  
RDSON  
ThSHDN  
445  
mΩ  
V
SHDN Threshold  
Output High  
Output Low  
0.9  
0.6  
0.3  
V
UVLO  
On Threshold  
Off Threshold  
VCOMP Trip  
2.74  
2.60  
2.92  
2. 77  
0.67  
11  
3.10  
2.96  
V
V
OVP  
ISS  
V
Softstart Current  
8
14  
µA  
3
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Min  
(Note 4)  
Typ  
(Note 5)  
Max  
(Note 4)  
Symbol  
θJA  
Parameter  
Conditions  
Units  
Thermal Resistance  
TSSOP, Package only  
LLP, Package only  
150  
45  
°C/W  
Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended  
to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.  
Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance,  
θ
JA, and the ambient temperature, TA. See the Electrical Characteristics table for the thermal resistance of various layouts. The maximum allowable power  
dissipation at any ambient temperature is calculated using: PD (MAX) = (TJ(MAX) − TA)/θJA. Exceeding the maximum allowable power dissipation will cause  
excessive die temperature, and the regulator will go into thermal shutdown.  
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5kresistor into each pin. The machine model is a 200pF capacitor discharged  
directly into each pin.  
Note 4: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). 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: Typical numbers are at 25°C and represent the most likely norm.  
Note 6: Bias current flows into FB pin.  
Note 7: Supply voltage, bias current product will result in aditional device power dissipation. This power may be significant. The thermal dissipation design should  
take this into account.  
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4
Typical Performance Characteristics  
Iq (non-switching) vs VIN @ fSW = 300kHz  
Iq (non-switching) vs VIN @ fSW = 700kHz  
20031920  
20031921  
Iq (switching) vs VIN @ fSW = 300kHz  
Iq (switching) vs VIN @ fSW = 700kHz  
20031922  
20031923  
Vfb vs Temperature  
RDS(ON) vs VIN @ ISW =1A  
20031924  
20031925  
5
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Current Limit vs Temperature  
Current Limit vs VIN  
20031926  
20031927  
fSW vs. VIN @ FS = Low (-3)  
fSW vs. VIN @ FS = OPEN (-3)  
20031928  
20031929  
fSW vs. Temperature @ FS = Low (-3)  
fSW vs. Temperature @ FS = OPEN (-3)  
20031931  
20031930  
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fSW vs. Temperature @ FS = Low (-6)  
fSW vs. Temperature @ FS = OPEN (-6)  
20031974  
20031975  
Error Amp. Transconductance vs Temp.  
BYP Pin Voltage vs VIN  
20031932  
20031933  
7
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20031953  
FIGURE 1. 300 kHz operation, 48V output  
20031954  
FIGURE 2. 700 kHz operation, 48V output  
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Block Diagram  
20031903  
end of the period and current flows through the inductor once  
again.  
Boost Regulator Operation  
The LM5000 utilizes a PWM control scheme to regulate the  
output voltage over all load conditions. The operation can best  
be understood referring to the block diagram and Figure 3. At  
the start of each cycle, the oscillator sets the driver logic and  
turns on the NMOS power device conducting current through  
the inductor, cycle 1 of Figure 3 (a). During this cycle, the  
voltage at the COMP pin controls the peak inductor current.  
The COMP voltage will increase with larger loads and de-  
crease with smaller. This voltage is compared with the sum-  
mation of the SW volatge and the ramp compensation.The  
ramp compensation is used in PWM architectures to eliminate  
the sub-harmonic oscillations that occur during duty cycles  
greater than 50%. Once the summation of the ramp compen-  
sation and switch voltage equals the COMP voltage, the PWM  
comparator resets the driver logic turning off the NMOS power  
device. The inductor current then flows through the output  
diode to the load and output capacitor, cycle 2 of Figure 3 (b).  
The NMOS power device is then set by the oscillator at the  
The LM5000 has dedicated protection circuitry running during  
the normal operation to protect the IC. The Thermal Shutdown  
circuitry turns off the NMOS power device when the die tem-  
perature reaches excessive levels. The UVP comparator pro-  
tects the NMOS power device during supply power startup  
and shutdown to prevent operation at voltages less than the  
minimum input voltage. The OVP comparator is used to pre-  
vent the output voltage from rising at no loads allowing full  
PWM operation over all load conditions. The LM5000 also  
features a shutdown mode. An external capacitor sets the  
softstart time by limiting the error amp output range, as the  
capacitor charges up via an internal 10µA current source.  
The LM5000 is available in two operating frequency ranges.  
The LM5000-3 is pin selectable for either 300kHz (FS  
Grounded) or 700kHz (FS Open). The LM5000-6 is pin se-  
lectable for either 600kHz (FS Grounded) or 1.3MHz (FS  
Open)  
9
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Operation  
20031902  
FIGURE 3. Simplified Boost Converter Diagram  
(a) First Cycle of Operation (b) Second Cycle Of Operation  
CONTINUOUS CONDUCTION MODE  
INTRODUCTION TO COMPENSATION  
The LM5000 is a current-mode, PWM regulator. When used  
as a boost regulator the input voltage is stepped up to a higher  
output voltage. In continuous conduction mode (when the in-  
ductor current never reaches zero at steady state), the boost  
regulator operates in two cycles.  
In the first cycle of operation, shown in Figure 3 (a), the tran-  
sistor is closed and the diode is reverse biased. Energy is  
collected in the inductor and the load current is supplied by  
COUT  
.
The second cycle is shown in Figure 3 (b). During this cycle,  
the transistor is open and the diode is forward biased. The  
energy stored in the inductor is transferred to the load and  
output capacitor.  
The ratio of these two cycles determines the output voltage.  
The output voltage is defined approximately as:  
where D is the duty cycle of the switch, D and Dwill be re-  
quired for design calculations.  
20031905  
SETTING THE OUTPUT VOLTAGE  
FIGURE 4. (a) Inductor current. (b) Diode current.  
The output voltage is set using the feedback pin and a resistor  
divider connected to the output as shown in Figure 1. The  
feedback pin is always at 1.259V, so the ratio of the feedback  
resistors sets the output voltage.  
The LM5000 is a current mode PWM regulator. The signal  
flow of this control scheme has two feedback loops, one that  
senses switch current and one that senses output voltage.  
To keep a current programmed control converter stable  
above duty cycles of 50%, the inductor must meet certain cri-  
teria. The inductor, along with input and output voltage, will  
determine the slope of the current through the inductor (see  
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10  
Figure 4 (a)). If the slope of the inductor current is too great,  
the circuit will be unstable above duty cycles of 50%.  
loop system that must be stabilized to avoid positive feedback  
and instability. A value for open-loop DC gain will be required,  
from which you can calculate, or place, poles and zeros to  
determine the crossover frequency and the phase margin. A  
high phase margin (greater than 45°) is desired for the best  
stability and transient response. For the purpose of stabilizing  
the LM5000, choosing a crossover point well below where the  
right half plane zero is located will ensure sufficient phase  
margin. A discussion of the right half plane zero and checking  
the crossover using the DC gain will follow.  
The LM5000 provides a compensation pin (COMP) to cus-  
tomize the voltage loop feedback. It is recommended that a  
series combination of RC and CC be used for the compensa-  
tion network, as shown in Figure 1. The series combination of  
RC and CC introduces pole-zero pair according to the follow-  
ing equations:  
OUTPUT CAPACITOR SELECTION  
The choice of output capacitors is somewhat more arbitrary.  
It is recommended that low ESR (Equivalent Series Resis-  
tance, denoted RESR) capacitors be used such as ceramic,  
polymer electrolytic, or low ESR tantalum. Higher ESR ca-  
pacitors may be used but will require more compensation  
which will be explained later on in the section. The ESR is also  
important because it determines the output voltage ripple ac-  
cording to the approximate equation:  
where RO is the output impedance of the error amplifier,  
850k. For most applications, performance can be optimized  
by choosing values within the range 5kRC 20kand  
680pF CC 4.7nF.  
ΔVOUT iLRESR (in Volts)  
After choosing the output capacitor you can determine a pole-  
zero pair introduced into the control loop by the following  
equations:  
COMPENSATION  
This section will present a general design procedure to help  
insure a stable and operational circuit. The designs in this  
datasheet are optimized for particular requirements. If differ-  
ent conversions are required, some of the components may  
need to be changed to ensure stability. Below is a set of gen-  
eral guidelines in designing a stable circuit for continuous  
conduction operation (loads greater than 100mA), in most all  
cases this will provide for stability during discontinuous oper-  
ation as well. The power components and their effects will be  
determined first, then the compensation components will be  
chosen to produce stability.  
Where RL is the minimum load resistance corresponding to  
the maximum load current. The zero created by the ESR of  
the output capacitor is generally very high frequency if the  
ESR is small. If low ESR capacitors are used it can be ne-  
glected. If higher ESR capacitors are used see the High  
Output Capacitor ESR Compensation section.  
INDUCTOR SELECTION  
To ensure stability at duty cycles above 50%, the inductor  
must have some minimum value determined by the minimum  
input voltage and the maximum output voltage. This equation  
is:  
RIGHT HALF PLANE ZERO  
A current mode control boost regulator has an inherent right  
half plane zero (RHP zero). This zero has the effect of a zero  
in the gain plot, causing an imposed +20dB/decade on the  
rolloff, but has the effect of a pole in the phase, subtracting  
another 90° in the phase plot. This can cause undesirable  
effects if the control loop is influenced by this zero. To ensure  
the RHP zero does not cause instability issues, the control  
loop should be designed to have a bandwidth of ½ the fre-  
quency of the RHP zero or less. This zero occurs at a fre-  
quency of:  
where fs is the switching frequency, D is the duty cycle, and  
RDSON is the ON resistance of the internal switch. This equa-  
tion is only good for duty cycles greater than 50% (D>0.5).  
The inductor ripple current is important for a few reasons. One  
reason is because the peak switch current will be the average  
inductor current (input current) plus ΔiL. Care must be taken  
to make sure that the switch will not reach its current limit  
during normal operation. The inductor must also be sized ac-  
cordingly. It should have a saturation current rating higher  
than the peak inductor current expected. The output voltage  
ripple is also affected by the total ripple current.  
where ILOAD is the maximum load current.  
SELECTING THE COMPENSATION COMPONENTS  
The first step in selecting the compensation components RC  
and CC is to set a dominant low frequency pole in the control  
loop. Simply choose values for RC and CC within the ranges  
given in the Introduction to Compensation section to set this  
pole in the area of 10Hz to 100Hz. The frequency of the pole  
created is determined by the equation:  
DC GAIN AND OPEN-LOOP GAIN  
Since the control stage of the converter forms a complete  
feedback loop with the power components, it forms a closed-  
11  
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where RO is the output impedance of the error amplifier,  
850k. Since RC is generally much less than RO, it does not  
have much effect on the above equation and can be neglected  
until a value is chosen to set the zero fZC. fZC is created to  
cancel out the pole created by the output capacitor, fP1. The  
output capacitor pole will shift with different load currents as  
shown by the equation, so setting the zero is not exact. De-  
termine the range of fP1 over the expected loads and then set  
the zero fZC to a point approximately in the middle. The fre-  
quency of this zero is determined by:  
mc 0.072fs (in A/s)  
Now RC can be chosen with the selected value for CC. Check  
to make sure that the pole fPC is still in the 10Hz to 100Hz  
range, change each value slightly if needed to ensure both  
component values are in the recommended range. After  
checking the design at the end of this section, these values  
can be changed a little more to optimize performance if de-  
sired. This is best done in the lab on a bench, checking the  
load step response with different values until the ringing and  
overshoot on the output voltage at the edge of the load steps  
is minimal. This should produce a stable, high performance  
circuit. For improved transient response, higher values of  
RC (within the range of values) should be chosen. This will  
improve the overall bandwidth which makes the regulator re-  
spond more quickly to transients. If more detail is required, or  
the most optimal performance is desired, refer to a more in  
depth discussion of compensating current mode DC/DC  
switching regulators.  
where RL is the minimum load resistance, VIN is the maximum  
input voltage, and RDSON is the value chosen from the graph  
"RDSON vs. VIN " in the Typical Performance Characteristics  
section.  
SWITCH VOLTAGE LIMITS  
In a flyback regulator, the maximum steady-state voltage ap-  
pearing at the switch, when it is off, is set by the transformer  
turns ratio, N, the output voltage, VOUT, and the maximum in-  
put voltage, VIN (Max):  
VSW(OFF) = VIN (Max) + (VOUT +VF)/N  
where VF is the forward biased voltage of the output diode,  
and is typically 0.5V for Schottky diodes and 0.8V for ultra-  
fast recovery diodes. In certain circuits, there exists a voltage  
spike, VLL, superimposed on top of the steady-state voltage .  
Usually, this voltage spike is caused by the transformer leak-  
age inductance and/or the output rectifier recovery time. To  
“clamp” the voltage at the switch from exceeding its maximum  
value, a transient suppressor in series with a diode is inserted  
across the transformer primary.  
HIGH OUTPUT CAPACITOR ESR COMPENSATION  
When using an output capacitor with a high ESR value, or just  
to improve the overall phase margin of the control loop, an-  
other pole may be introduced to cancel the zero created by  
the ESR. This is accomplished by adding another capacitor,  
CC2, directly from the compensation pin VC to ground, in par-  
allel with the series combination of RC and CC. The pole  
should be placed at the same frequency as fZ1, the ESR zero.  
The equation for this pole follows:  
If poor circuit layout techniques are used, negative voltage  
transients may appear on the Switch pin. Applying a negative  
voltage (with respect to the IC's ground) to any monolithic IC  
pin causes erratic and unpredictable operation of that IC. This  
holds true for the LM5000 IC as well. When used in a flyback  
regulator, the voltage at the Switch pin can go negative when  
the switch turns on. The “ringing” voltage at the switch pin is  
caused by the output diode capacitance and the transformer  
leakage inductance forming a resonant circuit at the sec-  
ondary(ies). The resonant circuit generates the “ringing” volt-  
age, which gets reflected back through the transformer to the  
switch pin. There are two common methods to avoid this  
problem. One is to add an RC snubber around the output rec-  
tifier(s). The values of the resistor and the capacitor must be  
chosen so that the voltage at the Switch pin does not drop  
below −0.4V. The resistor may range in value between 10Ω  
and 1 kΩ, and the capacitor will vary from 0.001 μF to  
0.1 μF. Adding a snubber will (slightly) reduce the efficiency  
of the overall circuit.  
To ensure this equation is valid, and that CC2 can be used  
without negatively impacting the effects of RC and CC, fPC2  
must be greater than 10fPC  
.
CHECKING THE DESIGN  
The final step is to check the design. This is to ensure a band-  
width of ½ or less of the frequency of the RHP zero. This is  
done by calculating the open-loop DC gain, ADC. After this  
value is known, you can calculate the crossover visually by  
placing a −20dB/decade slope at each pole, and a +20dB/  
decade slope for each zero. The point at which the gain plot  
crosses unity gain, or 0dB, is the crossover frequency. If the  
crossover frequency is at less than ½ the RHP zero, the phase  
margin should be high enough for stability. The phase margin  
can also be improved some by adding CC2 as discussed ear-  
lier in the section. The equation for ADC is given below with  
additional equations required for the calculation:  
The other method to reduce or eliminate the “ringing” is to  
insert a Schottky diode clamp between the SW pin and the  
PGND pin. The reverse voltage rating of the diode must be  
greater than the switch off voltage.  
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12  
OUTPUT VOLTAGE LIMITATIONS  
Flyback Regulator Operation  
The LM5000 is ideally suited for use in the flyback regulator  
topology. The flyback regulator can produce a single output  
voltage, or multiple output voltages.  
The maximum output voltage of a boost regulator is the max-  
imum switch voltage minus a diode drop. In a flyback regula-  
tor, the maximum output voltage is determined by the turns  
ratio, N, and the duty cycle, D, by the equation:  
The operation of a flyback regulator is as follows: When the  
switch is on, current flows through the primary winding of the  
transformer, T1, storing energy in the magnetic field of the  
transformer. Note that the primary and secondary windings  
are out of phase, so no current flows through the secondary  
when current flows through the primary. When the switch  
turns off, the magnetic field collapses, reversing the voltage  
polarity of the primary and secondary windings. Now rectifier  
D5 is forward biased and current flows through it, releasing  
the energy stored in the transformer. This produces voltage  
at the output.  
VOUT ≈ N × VIN × D/(1 − D)  
The duty cycle of a flyback regulator is determined by the fol-  
lowing equation:  
Theoretically, the maximum output voltage can be as large as  
desired—just keep increasing the turns ratio of the trans-  
former. However, there exists some physical limitations that  
prevent the turns ratio, and thus the output voltage, from in-  
creasing to infinity. The physical limitations are capacitances  
and inductances in the LM5000 switch, the output diode(s),  
and the transformer—such as reverse recovery time of the  
output diode (mentioned above).  
The output voltage is controlled by modulating the peak  
switch current. This is done by feeding back a portion of the  
output voltage to the error amp, which amplifies the difference  
between the feedback voltage and a 1.259V reference. The  
error amp output voltage is compared to a ramp voltage pro-  
portional to the switch current (i.e., inductor current during the  
switch on time). The comparator terminates the switch on time  
when the two voltages are equal, thereby controlling the peak  
switch current to maintain a constant output voltage.  
INPUT LINE CONDITIONING  
A small, low-pass RC filter should be used at the input pin of  
the LM5000 if the input voltage has an unusually large amount  
of transient noise. Additionally, the RC filter can reduce the  
dissipation within the device when the input voltage is high.  
20031972  
FIGURE 5. LM5000 Flyback Converter  
13  
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ITEM  
PART NUMBER  
C4532X7R2A105MT  
DESCRIPTION  
Capacitor, CER, TDK  
VALUE  
1µ, 100V  
C
C
C
C
C
C
C
C
C
C
C
1
2
3
C4532X7R2A105MT  
C1206C224K5RAC  
C1206C104K5RAC  
C1206C104K5RAC  
C1206C101K1GAC  
C1206C104K5RAC  
C4532X7S0G686M  
C4532X7S0G686M  
C1206C221K1GAC  
C1206C102K5RAC  
Capacitor, CER, TDK  
1µ, 100V  
Capacitor, CER, KEMET  
Capacitor, CER, KEMET  
Capacitor, CER, KEMET  
Capacitor, CER, KEMET  
Capacitor, CER, KEMET  
Capacitor, CER, TDK  
0.22µ, 50V  
0.1µ, 50V  
0.1µ, 50V  
100p, 100V  
0.1µ, 50V  
68µ, 4V  
4
5
6
7
8
9
Capacitor, CER, TDK  
68µ, 4V  
10  
11  
Capacitor, CER, KEMET  
Capacitor, CER, KEMET  
220p, 100V  
1000p, 500V  
D
D
D
D
D
1
2
3
4
5
BZX84C10-NSA  
CMZ5930B-NSA  
CMPD914-NSA  
CMPD914-NSA  
CMSH3-40L-NSA  
Central, 10V Zener, SOT-23  
Central, 16V Zener, SMA  
Central, Switching, SOT-23  
Central, Switching, SOT-23  
Central, Schottky, SMC  
T
1
A0009-A  
Coilcraft, Transformer  
R
R
R
R
R
R
R
1
2
3
4
5
6
7
CRCW12064992F  
CRCW12061001F  
CRCW12061002F  
CRCW12066191F  
CRCW120610R0F  
CRCW12062003F  
CRCW12061002F  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
49.9K  
1K  
10K  
6.19K  
10  
200K  
10K  
Q
U
1
1
CXT5551-NSA  
LM5000-3  
Central, NPN, 180V  
Regulator, National  
www.national.com  
14  
Physical Dimensions inches (millimeters) unless otherwise noted  
TSSOP-16 Pin Package (MTC)  
For Ordering, Refer to Ordering Information Table  
NS Package Number MTC16  
15  
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LLP-16 Pin Package (SDA)  
For Ordering, Refer to Ordering Information Table  
NS Package Number SDA16A  
www.national.com  
16  
Notes  
17  
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Notes  
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