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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter General Description
The TD1507 is a easy to use adjustable step-down (buck) switch-mode voltage regulators. The device is available in an adjustable output version. It is capable of driving a 2.5A load with excellent line and load regulation. Requiring a minimum number of external components, the regulator is simple to use and include internal frequency compensation, and a fixed-frequency oscillator. The output voltage is guaranteed to 3% tolerance under specified input voltage and output load conditions. The oscillator frequency is guaranteed to 15%. External shutdown is included, featuring typically 80 A 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. The TD1507 is available in TO252-5L package.
TD1507
Features
* * * * * * * * * * * Adjustable output version Output adjustable from 1.23v to 34V Fixed 150KHz frequency internal oscillator Guaranteed 2.5A output load current Input voltage range up to 36V Low power standby mode, IQ typically 70 A TTL shutdown capability Excellent line and load regulation High efficiency Thermal shutdown and current limit protection Available in TO252-5L package
Applications
* * * * * * * 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 3.3V for microprocessors
Package Types
TO252-5L
Figure 1. Package Types of TD1507
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Pin Descriptions TD1507
Pin Assignments
Name Vin
5 ON/OFF 4 Feedback 3 Gnd 2 Output 1 Vin
Description Input supply voltage Switching output Ground Output voltage feedback ON/OFF shutdown Active is "Low" or floating
Output Gnd Feedback
TO252-5L
ON/OFF
Ordering Information
TD1507
X
X
Circuit Type
Packing Blank: Tube R: Tape and Reel
Package T: TO252-5L
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Functional Block Diagram TD1507
Figure 2. Functional Block Diagram of TD1507
Typical Application
Figure 3. Typical Application of TD1507
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Absolute Maximum Ratings
Note1: Stresses greater than those listed under Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
TD1507
Parameter Supply Voltage Vin Feedback VFB pin voltage ON/OFF Pin voltage Output pin voltage Output Voltage to Ground (Steady State) Power Dissipation Operating Temperature Range Storage Temperature Lead Temperature (Soldering, 10 sec) ESD(HM)
Value -0.3 to 40 -0.3 to Vin+0.3 -0.3 to Vin+0.3 -0.3 to Vin+0.3 -1 Internally limited -40 to +125 -65 to +150 200 2000
Unit V V V V V W C C C V
Electrical Characteristics
Unless otherwise specified, Vin = 12V. Iload = 0.5A, Ta = 25. Symbol Ib IQ ISTBY FOSC VSAT ICL IL IL VIL VIH IH Parameter Feedback bias current Quiescent current
Standby quiescent current
Conditions VFB=1.3V VFB=12V force driver off ON/OFF=5V, VIN=36V
Min.
Typ. 10 5 70
Max. 50/100 10 150 173 1.4/1.5 5.5/6.5 50
Unit nA mA uA KHz V A uA mA V V
Oscillator frequency Saturation voltage Current Limit Output leakage current Output leakage current ON/OFF pin logic input Threshold voltage
ON/OFF pin input current
127 IOUT=2A Peak Current (VFB=0V) Output=0V (VFB=12V) Output=-1V (VIN=36V) Low (Regulator ON) High (Regulator OFF)
VLOGIC=2.5V(Regulator OFF)
150 1.10 4.5
2 1.3 2.0 1.3 5
30 0.6
15
uA
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter
IL JC JA TD1507 ADJ Thermal Resistance Junction to Case Thermal Resistance Junction to Ambient (Note1) Vfb: Output Voltage : Efficiency
VLOGIC=0.5V(Regulator ON)
TD1507
0.02 10 50 1.193/ 1.180 1.267/ 1.280 5 uA
O
TO252-5L TO252-5L 11VVIN 36V, 0.2AILOAD 3A, VOUT for 9V VIN=12V,VOUT=9V,ILOAD=3A
C/W C/W
O
1.23 88
V %
Specifications with boldface type are for full operationg temperature range, the other type are for TJ=25OC. Note1: Thermal resistance with copper area of approximately 3 in2.
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Typical Performance Characteristics TD1507
Figure 4. Output Voltage vs. Temperature
Figure 5. Switching Frequency vs. Temperature
Figure 6. Output Saturation Characteristics
Figure 7. Quiescent Current vs. Temperature
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter TD1507
Figure 8. ON/OFF Pin Voltage
Figure 9. ON/OFF Pin Sink Current
Figure 10. Output Saturation Characteristics
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Typical Application Circuit TD1507
Figure 11. Typical Application of TD1507
Vout 3.3V 5V 9V 12V
R1 1.6K 3.6K 6.8K 1.5K
R2 2.7K 11K 43K 13K
Cf (Operational) 33nf 10nf 1.5nf 1nf
Table 1. Vout VS. R1, R2, Cf Select Table Output Voltage 3.3V 5V 9V 12V Input Voltage 6V ~ 18V 6V ~36V 8V ~ 18V 8V ~36V 12V ~18V 12V ~36V 15V ~ 18V 15V ~36V Inductor (L1) 47uh 68uh 33uh 47uh 47uh 47uh 47uh 47uh Output Capacitor (Cout) Through Hole Electrolytic 470uf/25V 560uf/25V 330uf/25V 470uf/25V 330uf/25V 470uf/25V 220uf/25V 330uf/25V
Table 2. Typical Application Buck Regulator Design Procedure
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Function Description
Pin Functions +VIN
This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator
TD1507
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. The TO252 surface mount package tab is designed to be soldered to the copper on a printed circuit board. The copper and the board are the heat sink for this package and the other heat producing components, such as the catch diode and inductor. The PC board copper area that the package is soldered to should be at least 0.4 in2, and ideally should have 2 or more square inches of 2 oz. Additional copper area improves the thermal characteristics, but with copper areas greater than approximately 6 in2, only small improvements in heat dissipation are realized. If further thermal improvements are needed, double sided, multilayer PC board with large copper areas and/or airflow are recommended. The TD1507 (TO252 package) junction temperature rise above ambient temperature with a 2.5A load for various input and output voltages. This data was taken with the circuit operating as a buck switching regulator with all components mounted on a PC board to simulate the junction temperature under actual operating conditions. This curve can be used for a quick check for the approximate junction temperature for various conditions, but be aware that there are many factors that can affect the junction temperature. When load currents higher than 2.5A are used, double sided or multilayer PC boards with large copper areas and/or airflow might be needed, especially for high ambient temperatures and high output voltages. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (Once exception to this is the output (switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further.
Ground
Circuit ground.
Output
Internal switch. The voltage at this pin switches between (+VIN - VSAT) and approximately - 0.5V, with a duty cycle of approximately VOUT / VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept a minimum.
Feedback
Senses the regulated output voltage to complete the feedback loop.
ON/OFF
Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 80uA. 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.
Thermal Considerations
The TD1507 is available in TO252-5L package. The TO252 package needs a heat sink under most conditions. The size of the heatsink depends on the input voltage, the output voltage, the load current and the ambient temperature. The TD1507 junction temperature rises above ambient temperature for a 2.5A load and different input and output voltages. The data for these curves was taken with the TD1507 (TO252
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter Package Information TD1507
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Datasheet 2.5A 150KHZ PWM Buck DC/DC Converter TD1507
Design Notes
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