step-down converter TD1501 海之星科技

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, I_Q 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

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

+V_IN

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 (+V_IN – V_SAT) and approximately – 0.5V, with a duty cycle of approximately V_OUT / V_IN. 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	V_IN	-0.3 to 45	V

Feedback Pin Voltage	V_FB	-0.3 to 40	V

Enable Pin Voltage	Von-off	-0.3 to 25	V

Output Voltage to Ground (Steady State)	V_OUT	-1	V

Power Dissipation	P_D	Internally limited	mW

Operating Junction Temperature	T_J	150	°C

Storage Temperature	T_STG	-65 to 150	°C

Lead Temperature (Soldering, 10 sec)	T_LEAD	260	°C

ESD(HBM)	V_ESD	2000	V

Recommended Operating Conditions

Parameter	Symbol	Min.	Max.	Unit
Input Voltage	V_IN	3.6	45	V
Operating Junction Temperature	T_J	-40	125	°C
Operating Ambient Temperature	T_A	-40	85	°C

Electrical Characteristics

(All Output Voltage Versions)
Unless otherwise specified, VIN = 12V for 3.3V, 5V, adjustable version . I_LOAD= 0.5A Ta = 25°C.

Symbol	Parameter		Conditions		Min.	Typ.	Max.	Unit
V_IN	Input voltage				4.5		45	V
I_Q	Quiescent current		V_FB=12V force driver off			3	4	mA
I_L	Output=0V	Output leakage current	No outside circuit V_FB=12V force driver off				50	uA
I_L	Output=-1V	Output leakage current	V_IN=40V			2	30	mA
I_STBY	Standby quiescent current		ON/OFF pin=5V, V_IN=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
V_SAT	Saturation voltage		I_OUT=3A No outside circuit V_FB= 0V force driver on			1.16	1.4	V
DC	Min. Dyty Cycle (ON)		V_FB=12V force driver on			100		%
DC	Min. Dyty Cycle (OFF)		V_FB=12V force driver off			0		%
V_FB	Feedback Voltage		V_IN= 4.5V to 45V		1.21	1.235	1.26	V
I_FB	Feedback bias current		V_FB=1.3V (Adjustable version only)			10	50	nA
I_CL	Current Limit		Peak Current (V_FB=0V)			3.8	5.5	A
V_H	ON/OFF pin logic input Threshold votage		Low (Regulaor ON)			1.3	0.6	V
V_L	ON/OFF pin logic input Threshold votage		High (Regulator OFF)		2.0	1.3		V
I_H	ON/OFF pin logic input current		V_LOGIC=2.5V(ON)				-0.01	uA
I_L	ON/OFF pin input current		V_LOGIC=0.5V(ON)			-0.1		uA
θ_JC	Thermal Resistance		TO220B-5L TO263-5L	Junction to Case		2.5 3.5		^OC/W
θ_JA	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	V_Min	Typ.	V_MAX	Unit
TD1501 3.3	Vout	Output Feedback	4.75V≦V_IN≦45V 0.2A≦I_LOAD≦3A	3.168 3.135	3.3	3.432 4.465	V
TD1501 3.3	η	Efficiency	V_IN=12V,I_LOAD=3A		73		%
TD1501 5.0	Vout	Output Feedback	7V≦V_IN≦45V 0.2A≦I_LOAD≦3A	4.8 4.75	5.0	5.200 5.250	V
TD1501 5.0	η	Efficiency	V_IN=12V,I_LOAD=3A		80		%
TD1501 ADJ	V_FB	Output Feedback	4.5V≦V_IN≦45V 0.2A≦I_LOAD≦3A V_OUTprogrammed for 3V	1.193 1.180	1.23	1.267 1.280	V
TD1501 ADJ	η	Efficiency	V_IN=12V,I_LOAD=3A		73		%
TD1501 ADJ	Vout	Output Voltage	15V≦V_IN≦45V 0.2A≦I_LOAD≦3A V_OUTprogrammed for 12V	11.52 11.4	12	12.48 12.6	V
TD1501 ADJ	η	Efficiency	V_IN=25V,I_LOAD=3A		90		%

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

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
Vin (Max)	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
Vin (Max)	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 25^oC (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 C_OUT 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
Symbol	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
Symbol	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

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

General Description

Features

Applications

Package Types

Pin Assignments

Pin Descriptions

Ordering Information

Function Description

Pin Functions

+V_IN

GND

Output

Feedback

ON/OFF

Functional Block Diagram

Typical Application

Absolute Maximum Ratings

Recommended Operating Conditions

Electrical Characteristics

Electrical Characteristics ( Continued )

Typical Performance Characteristics

Schottky Rectifier Selection Guide

Application Hints and Layout Guidelines

Heat Sink / Thermal Considerations

Output Voltage Ripple and Transients

Layout Guidelines

Packing Information

TO263-5L Carrier Tape Outline Dimensions

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

General Description

Features

Applications

Package Types

Pin Assignments

Pin Descriptions

Ordering Information

Function Description

Pin Functions

+VIN

GND

Output

Feedback

ON/OFF

Functional Block Diagram

Typical Application

Absolute Maximum Ratings

Recommended Operating Conditions

Electrical Characteristics

Electrical Characteristics ( Continued )

Typical Performance Characteristics

Schottky Rectifier Selection Guide

Application Hints and Layout Guidelines

Heat Sink / Thermal Considerations

Output Voltage Ripple and Transients

Layout Guidelines

Packing Information

TO263-5L Carrier Tape Outline Dimensions

+V_IN