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TD1501 3A 150KHZ 45V PWM Buck DC/DC Converter

General Description 

The TD1501 is a of easy to use adjustable step-down (buck) switch-mode DC/DC converter. The device is available in an adjustable or fixed output version. It is capable of driving a 3A 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 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. 

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation, and a fixed-frequency oscillator.

The TD1501 is available in TO-220B-5L and TO-263-5L packages.

 

Features  

•Voltage mode non-synchronous PWM control

•Built- in switching transistor on chip

•Guaranteed 3A output load current

•Input voltage range up to 45V

•3,3V,5V and Adjustable output versions

•adjustable version output from 1.23V to 42V

•Fixed 150KHz frequency internal oscillator

•Up to 90% efficiency

•ON/OFF shutdown control input

•Low power standby mode, IQ typically 80 µA

•Thermal shutdown , current limit and short circuit protection

•Available in TO-220B and TO-263 packages

•RoHS Compliant (100% Green available)

•The minimum dropout @ Vout=5V/0.5A  up to 0.9 V

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 1.8/2.5/3.3/5.0 V for microprocessors

   

 


Package Types

 
TO220B-5L TO220-5L TO263-5L
Figure 1. Package Types of TD1501

 Pin Assignments  

TO220B-5L/TO220-5L

TO263-5L

 

Pin Descriptions

 
Name Description
Vin Input supply voltage
Output Switching output
Gnd Ground
Feedback Output voltage feedback input
ON/OFF ON/OFF shutdown Active is“Low”or Ground
 

 

Ordering Information


 

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.  

GND

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. 

Functional Block Diagram

 
Figure 2. Functional Block Diagram of TD1501  

Typical Application






Figure 3. Typical Application of TD1501

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.
 
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

Recommended Operating Conditions

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

Electrical Characteristics

(All Output Voltage Versions)
Unless otherwise specified, VIN = 12V for 3.3V, 5V, adjustable version . ILOAD= 0.5A Ta = 25°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   80 200 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=3A No outside circuit VFB= 0V force driver on   1.16 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

 5.5 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 TO220B-5L
TO263-5L		 Junction to Case   2.5
3.5		   OC/W
θJA Thermal Resistance with a copper area of approximately 3 in2 TO220B-5L
TO263-5L		 Junction to Ambient   28
23		   OC/W

Electrical Characteristics  ( Continued )

  Symbol Parameter Conditions VMin Typ. VMAX Unit
TD1501 3.3 Vout Output Feedback 4.75V≦VIN≦45V
0.2A≦ILOAD≦3A 		3.168
3.135		 3.3 3.432
4.465		 V
η Efficiency VIN=12V,ILOAD=3A   73   %
TD1501 5.0 Vout Output Feedback 7V≦VIN≦45V
0.2A≦ILOAD≦3A 		4.8
4.75		 5.0 5.200
5.250		 V
η Efficiency VIN=12V,ILOAD=3A   80   %
TD1501 ADJ VFB Output Feedback 4.5V≦VIN≦45V
0.2A≦ILOAD≦3A
VOUT programmed for 3V		 1.193
1.180		 1.23 1.267
1.280		 V
η Efficiency VIN=12V,ILOAD=3A   73   %
TD1501 ADJ Vout Output Voltage 15V≦VIN≦45V
0.2A≦ILOAD≦3A
VOUT programmed for 12V		 11.52
11.4		 12 12.48
12.6		 V
η Efficiency VIN=25V,ILOAD=3A   90   %

 Specifications with boldface type are for full operationg temperature range, the other type are for TJ=25OC.  

 

Typical Performance Characteristics

Figure 4. Efficiency vs. Load (Vin=12V) Figure 5. Output Voltage vs. Temperature
 
Figure 6. Output Saturation Characteristics Figure 7.Switching Frequency vs. Temperature

 

Figure 8. Quiescent Current vs Temperature Figure 9. ON/OFF Pin Voltage

Figure 10. ON/OFF Pin Sink Current Figure 11. Output Saturation Characteristics


Typical Application Circuit  (Adjustable Output Voltage Version)



Figure 13.Typical Application of TD1501 for ADJ

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
Table 3. Vout VS. R1, R2, Cf Select Table

 

Schottky Rectifier Selection Guide

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
 
Vin
(Max)		 4A Load Current 5A Load Current
Part Number Package Vendor Part Number Package Vendor
20v SL42 SMC 2,3 B520C SMC 1
      SR502 DO-201AD 1
      SB520 DO-201AD 2
      IN5823 DO-201AD 6
30V SL43 SMC 2,3 B530C SMC 1
      SR503 DO-201AD 1
      SB530 DO-201AD 2
      SSC53L SMC 3
      IN5824 D0-201AD 6
40V SL44 SMC 2,3,5 B540C SMC 1
      SR504 DO-201AD 1
      SB540 DO-201AD 2
      SSC54 SMC 3
      IMBRS540T3 SMC 5
      IN5825 DC-201AD 6
50V       B550C DC-201AD 6
      SB550 SMC 1
        DC-201AD 2
           
Table 5  Lists some rectifier manufacturers.


Application Hints and Layout Guidelines

Heat Sink / Thermal Considerations

The TD1501 is available in two packages, a 5-pin TO-220B/TO220 and a 5-pin surface mount TO-263.

The TO-220B/TO220 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 TD1501 junction temperature rises above ambient temperature for a 3A load and different input and output voltages.  The data for these curves was taken with the TD1501 (TO-220B/TO220 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 TO-263 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 TD1501 (TO-263 package) junction temperature rise above ambient temperature with a 3A 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 3A 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.

Output Voltage Ripple and Transients

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. 

Layout Guidelines 

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 (TO220B-5L)

 


 

Symbol Dimensions In Millimeters Dimensions In Inches
Min. Max. Min. Max.
A 0.44 0.47 0.175 0.185
b 0.07 0.09 0.027 0.037
D 0.84 0.89 0.33 0.35
d1 0.1 0.039
d2 0.63 0.248
E 9.91 10.41 0.39 0.41
e 0.16 0.18 0.062 0.072
F 0.12 0.13 0.048 0.052
H1 0.64 0.25
H2 2.08 2.24 0.82 0.88
H3 2.39 2.55 0.942 1.002
J1 0.27 0.105
J2 0.37 0.53 0.147 0.207
J3 0.84 0.331
Q 0.25 0.3 0.1 0.12

Package Information(TO220-5L)

 

Package Information (TO263-5L) 

 

 

Symbol Dimensions In Millimeters Dimensions In Inches
Min. Max. Min. Max.
A 4.06 4.83 0.16 0.19
B 0.76 1.02 0.03 0.04
C 0.36 0.64 0.014 0.025
C2 1.14 1.4 0.045 0.055
D 8.64 9.65 0.34 0.38
E 9.78 10.54 0.385 0.415
e 1.57 1.85 0.062 0.073
F 6.6 7.11 0.26 0.28
L 15.11 15.37 0.595 0.605
L2 - 1.4 - 0.055
 

Packing Information

TO263-5L Carrier Tape Outline Dimensions



Carrier Tape, Number of Components Per Reel and Reel Size

Package Carrier Width (W) Pitch (P) Part Per Full Real Real Size
TO263-5L 24.0 ± 0.1mm 4.0 ± 0.1mm 800 PCS 330 ± 2mm