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The TD1509 is a of easy to use adjustable step-down (buck) switch-mode DC/DC regulator. The device is available in an adjustable or fixed output version. It is capable of driving a 2A load with excellent line and load regulation.
The output voltage is guaranteed to ±3% tolerance under specified input voltage and output load conditions. The oscillator frequency is guaranteed to ±15%. The PWM control circuit is able to adjust the duty ratio linearly from 0 to 100%. External shutdown is included, featuring typically 50 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.
Requiring a minimum number of external
components, these regulators are simple to use
and include internal frequency compensation, and
a fixed-frequency oscillator.
The TD1509 is available in SOP8 package.
• Voltage mode non-synchronous PWM control
• Built- in switching transistor on chip
• Guaranteed 2A output load current
• Input voltage range up to 45V
• 3,3V,5V and Adjustable output versions
• adjustable version output from 1.23V to 43V
• Fixed 150KHz frequency internal oscillator
• Up to 90% efficiency
• ON/OFF shutdown control input
• Low power standby mode, IQ typically 50 μA
• Thermal shutdown , current limit and short circuit protection
• SOIC-8 Package is Available
• RoHS Compliant (100% Green available)
• The minimum dropout @ Vout=5V/0.5A up to 0.9 V
•Simple High-efficiency step-down regulator
•On-card switching regulators
•Positive to negative converter•LCD monitor and LCD TV
•DVD recorder and PDP TV
•Battery charger
•Step-down to 1.5/1.8/2.5/3.3/5.0 V for microprocessors
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| SOP8 |
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| SOP8 |
| Pin | Name | Description |
|---|---|---|
| 1 | Vin | Input supply voltage |
| 2 | Output | Switching output |
| 5~8 | Gnd | Ground |
| 3 | Feedback | Output voltage feedback input |
| 4 | ON/OFF | ON/OFF shutdown Active is“Low”or Ground |
Circuit ground.
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Input Voltage | VIN | -0.3 to 45 | V |
| Feedback Pin Voltage | VFB | -0.3 to 40 | V |
| Enable Pin Voltage | Von-off | -0.3 to 25 | V |
| Output Voltage to Ground (Steady State) | VOUT | -1 | V |
| Power Dissipation | PD | Internally limited | mW |
| Operating Junction Temperature | TJ | 150 | °C |
| Storage Temperature | TSTG | -65 to 150 | °C |
| Lead Temperature (Soldering, 10 sec) | TLEAD | 260 | °C |
| ESD(HBM) | VESD | 2000 | V |
| Parameter | Symbol | Min. | Max. | Unit |
|---|---|---|---|---|
| Input Voltage | VIN | 3.6 | 45 | V |
| Operating Junction Temperature | TJ | -40 | 125 | °C |
| Operating Ambient Temperature | TA | -40 | 85 | °C |
| Symbol | Parameter | Conditions | Min. | Typ. | Max. | Unit | ||
|---|---|---|---|---|---|---|---|---|
| VIN | Input voltage | 4.5 | 45 | V | ||||
| IQ | Quiescent current | VFB=12V force driver off | 3 | 4 | mA | |||
| IL | Output=0V | Output leakage current |
No outside circuit VFB=12V force driver off |
50 | uA | |||
| Output=-1V | VIN=40V | 2 | 30 | mA | ||||
| ISTBY | Standby quiescent current | ON/OFF pin=5V, VIN=32V | 50 | 150 | uA | |||
| Fosc | Oscillator Frequency |
125 | 150 | 170 | KHz | |||
| Fscp | Oscillator Frequency of Short Circuit Protect | When current limit occurred and VFB < 0.5V, Ta = 25℃ | 10 | 30 | 50 | KHz | ||
| VSAT | Saturation voltage |
IOUT=2A No outside circuit VFB= 0V force driver on | 1.25 | 1.4 | V | |||
| DC | Min. Dyty Cycle (ON) | VFB=12V force driver on | 100 | % | ||||
| Min. Dyty Cycle (OFF) | VFB=12V force driver off | 0 | ||||||
| VFB | Feedback Voltage | VIN= 4.5V to 45V | 1.21 | 1.235 | 1.26 | V | ||
| IFB | Feedback bias current | VFB=1.3V (Adjustable version only) |
10 | 50 | nA | |||
| ICL | Current Limit | Peak Current (VFB=0V) | 3.8 |
A | ||||
| VH | ON/OFF pin logic input Threshold votage | Low (Regulaor ON) | 1.3 | 0.6 | V | |||
| VL | High (Regulator OFF) | 2.0 | 1.3 | V | ||||
| IH | ON/OFF pin logic input current | VLOGIC=2.5V(ON) | -0.01 | uA | ||||
| IL | ON/OFF pin input current | VLOGIC=0.5V(ON) | -0.1 | uA | ||||
| θJC | Thermal Resistance | SOP8-8L | Junction to Case | 15 | OC/W | |||
| θJA | Thermal Resistance with a copper area of approximately 3 in2 | SOP8-8L | Junction to Ambient | 70 | OC/W | |||
| Symbol | Parameter | Conditions | VMin | Typ. | VMAX | Unit | |
|---|---|---|---|---|---|---|---|
| TD1509 3.3V | Vout | Output Feedback | 4.75V≦VIN≦45V 0.2A≦ILOAD≦2A |
3.168 3.135 |
3.3 | 3.432 4.465 |
V |
| η | Efficiency | VIN=12V,ILOAD=2A | 78 | % | |||
| TD1509 5.0V | Vout | Output Feedback | 7V≦VIN≦45V 0.2A≦ILOAD≦2A |
4.8 4.75 |
5.0 | 5.200 5.250 |
V |
| η | Efficiency | VIN=12V,ILOAD=2A | 83 | % | |||
| TD1509 ADJ | VFB | Output Feedback | 4.5V≦VIN≦45V 0.2A≦ILOAD≦2A VOUT programmed for 3V |
1.193 1.180 |
1.23 | 1.267 1.280 |
V |
| η | Efficiency | VIN=12V,ILOAD=2A | 73 | % | |||
| TD1509 ADJ | Vout | Output Voltage | 15V≦VIN≦45V 0.2A≦ILOAD≦2A VOUT programmed for 12V |
11.52 11.4 |
12 | 12.48 12.6 |
V |
| η | Efficiency | VIN=25V,ILOAD=2A | 90 | % |
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| Figure 4. Efficiency vs. Load (Vin=12V) | Figure 5. Output Voltage vs. Temperature |
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| Figure 6. Output Saturation Characteristics | Figure 7.Switching Frequency vs. Temperature |
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| Figure 8. Quiescent Current vs Temperature | Figure 9. ON/OFF Pin Voltage |
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| Figure 10. ON/OFF Pin Sink Current | Figure 11. Output Saturation Characteristics |
Typical Application Circuit (Adjustable Output Voltage Version)
| Vout | R1 | R2 | Cf(Optinal) |
3.3V |
1.6K | 2.7K | 33nf |
| 5V | 3.6K | 11K | 10nf |
| 9V | 6.8K | 43K | 1.5nf |
| 12V | 1.5K | 13K | 1nf |
| Output Voltage | Input Voltage | Inductor (L1) | Output Component | |
|---|---|---|---|---|
| Through Hole Electrolytic (Cout) |
Schottky Diode (D1) |
|||
| 3.3V | 4.5V~18V | 47uh | 470uf/25V | ref. Table 5 |
| 18V~45V | 68uh | 560uf/25V | ||
| 5V | 7V~18V | 33uh | 330uf/25V | |
| 18V~45V | 47uh | 470uf/25V | ||
| 9V | 12V~18V | 47uh | 330uf/25V | |
| 18V~45 | 47uh | 470uf/25V | ||
| 12V | 15V~18V | 47uh | 220uf/25V | |
| 18V~45V | 47uh | 330uf/25V | ||
| Vin (Max) |
2A Load Current | 3A Load Current | ||||
|---|---|---|---|---|---|---|
| Part Number | Package | Vendor | Part Number | Package | Vendor | |
| 20V | B220/A | SMB/SMA | 1 | B320/B/A | SMC/B/A | 1 |
| SS22 | SMA | 2,3 | SS32 | SMC | 2,3 | |
| MBRS320 | SMC | 4 | ||||
| SK32 | SMC | 6 | ||||
| IN5820 | D0-201AD | 6 | ||||
| 30V | B230/A | SMB | 1 | B330/B/A | SMC/B/A | 1 |
| SS23 | SMB | 2,3 | SS33 | SMC | 2,3 | |
| 20BQ030 | SMB | 4 | MBRS330 | SMC | 4,5 | |
| MBRS230 | SMB | 5 | SK33 | SMC | 3,6 | |
| SK23 | SMB | 6 | IN5821 | D0-201AD | 2,6 | |
| 40V | B240/A | SMB/SMA | 1 | B340/B/A | SMC/B/A | 1 |
| SS24 | SMB | 1,3,5 | SS34 | SMC | 2,3 | |
| MBRS240 | SMB | 5 | Q0BQ040 | SMC | 4 | |
| MBRS340TR | SMC | 4,5 | ||||
| SK34 | SMC | 6 | ||||
| IN5822 | D0-201AD | 6 | ||||
| 50V | B250 A | SMB/SMA | 1 | B350/B/A | SMC/B/A | 1 |
| SS25 | SMB | 2,3 | SS35 | SMC | 2,3 | |
| SK23 | SMB | 5 | MBRS330 | SMC | 4,5 | |
| SK35 | SMC | 3.6 | ||||
| No. | Vendor | Web Site |
|---|---|---|
| 1 | Diodes,Inc. | www.diodes.com |
| 2 | Fairchild Semiconductor | www.fairchildsemi.com |
| 3 | General Semiconductor | www.gensemi.com |
| 4 | nternational Rectifier | www.irf.com |
| 5 | On Semiconductor | www.onsemi.com |
| 6 | Pan Jit International | www.panjit.com.tw |
The TD1509 is available in SOP8 package.
The SOP8 package needs a heat sink under most conditions. The size of the heat sink depends on the
input voltage, the output voltage, the load current and the ambient temperature. The TD1509 junction
temperature rises above ambient temperature for a 2A load and different input and output voltages. The
data for these curves was taken with the TD1509 (SOP8 package) operating as a buck-switching
regulator in an ambient temperature 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.
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.
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.
The output voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher frequency, typically about 1% of the output voltage, and may also contain short voltage spikes at the peaks of the sawtooth waveform.
The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by the ESR of the output capacitor.
The voltage spikes are present because of the fast switching action of the output switch, and the parasitic inductance of the output filter capacitor, To minimize these voltage spikes, special low inductance capacitors can be used, and their lead lengths must be kept short. Wiring inductance, stray capacitance, as well as the scope probe used to evaluate these transients, all contribute to the amplitude of these spikes.
A large value inductor will also result in lower output ripple voltage , but will have a larger physical size,higher series reistance,and/or lower saturation current. An additional small LC filter can be added to the output (as shown in Figure 14) to further reduce the amount of output ripple and transients.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 IC 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, IC 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 form the inductor especially an open core type of inductor.
Figure 14, Layout Guidelines and Post Ripple Filter
Package Information
SOP8 Package Outline Dimensions
