Texas Instruments TPS79801DCQEVM-434 User manual

User's GuideSLUU346 – June 2009
TPS79801DCQEVM-434
This user’s guide describes the characteristics, operation, and use of the TPS79801DCQEVM-434evaluation module (EVM). This EVM demonstrates the Texas Instruments TPS79801, a low-dropout linearregulator in a SOT223-5 package that is capable of 50 mA of output current. This document includessetup instructions, a schematic diagram, thermal guidelines, a bill of materials, and printed-circuit boardlayout drawings for the EVM.
Contents1 Introduction ................................................................................................................... 22 Setup .......................................................................................................................... 22.1 Input / Output Connector Descriptions ........................................................................... 23 Operation ..................................................................................................................... 33.1 Operation ............................................................................................................ 33.2 Fixed Output TPS798xx............................................................................................ 34 Thermal Guidelines .......................................................................................................... 34.1 Thermal Considerations ............................................................................................ 35 Board Layout ................................................................................................................. 46 Schematic and Bill of Materials ........................................................................................... 66.1 Schematic ............................................................................................................ 66.2 Bill of Materials ...................................................................................................... 7
List of Figures
1 Top Layer Assembly ......................................................................................................... 42 Top Layer Routing ........................................................................................................... 53 Bottom Layer Routing ....................................................................................................... 54 Bottom Layer Assembly ..................................................................................................... 65 TPS79801DCQEVM-434 Schematic ..................................................................................... 6
List of Tables
1 Output Voltage Setting ...................................................................................................... 22 TPS79801DCQEVM-434 Bill of Materials ............................................................................... 7
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1 Introduction
2 Setup
2.1 Input / Output Connector Descriptions
2.1.1 J1 –VIN
2.1.2 J2 –VOUT
2.1.3 J3 – GND
2.1.4 J4 – GND
2.1.5 J5 – ENABLE
2.1.6 J6 – Output Voltage Selection
Introduction www.ti.com
The TPS79801DCQEVM-434 evaluation module (EVM) helps designers evaluate the operation andperformance of the TPS79801 low-dropout (LDO) linear regulator in the SOT223-5 package. TheTPS79801 is a 50-mA, micropower, linear regulator.
This section describes the jumpers and connectors on the EVM as well as how to properly connect, setup, and use the TPS79801EVM.
This is the positive input supply voltage. Twist the leads to the input supply, and keep them as short aspossible to minimize EMI transmission. Add bulk capacitance between J1 and J3 if the supply leads aregreater than six inches. An additional 47- µF or greater capacitor improves the transient response of theTPS79801 and helps to reduce ringing on the input when long supply wires are used.
This is the positive connection from the output. Connect this pin to the positive input of the load.
This is the return connection for the input power supply of the regulator.
This is the return connection for the output.
This jumper is used to enable or disable the output of the TPS79801. Placing a shorting jumper betweenpins 1 and 2 (ON position) enables the TPS79801. Placing the shorting jumper between pins 2 and 3(OFF position) disables the TPS79801.
This jumper is used to select the output voltage of the TPS79801. The jumper selects different feedbackresistors to change the output voltage setting. The output voltage is set by inserting a shorting jumperacross two pins of J6. The preprogrammed output voltages are configured as shown in Table 1 .
Table 1. Output Voltage Setting
Output Voltage Jumper Between Pins
12 1 and 25 3 and 43.3 5 and 62.5 7 and 8
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3 Operation
3.1 Operation
3.2 Fixed Output TPS798xx
4 Thermal Guidelines
4.1 Thermal Considerations
www.ti.com Operation
Other output voltages can be configured by changing the feedback resistors on the board.
The pins of J6 connect directly to the feedback network of the TPS79801. The feedback network is highimpedance and sensitive to noise or resistance value changes. Do not touch the pins of J6 while thedevice is powered because the impedance of a human is enough to alter the output voltage set point. Theoutput voltage may increase or decrease if J6 is touched which may damage any load connected to theEVM.
This section provides information about the operation of the TPS79801EVM.
Connect the positive input power supply to J1. Connect the input power return (ground) to J3. TheTPS79801EVM has an absolute maximum input voltage of 82 V. The recommended maximum operatingvoltage is 80 V. The actual highest input voltage may be less than 80 V due to thermal conditions. See theThermal Considerations section of this manual to determine if the highest input voltage.
Connect the desired load between J2 (positive lead) and J4 (negative or return lead). Configure jumper J6for the desired output voltage. The function of J6 is described in the Setup section of this manual.
The TPS79801EVM can be used to evaluate fixed output voltage versions of the TPS798xx. The boardlayout and part footprints are the same between the adjustable version and fixed output voltage versionsof the TPS798. To evaluate a fixed output voltage version, the integrated circuit (IC) on the board needs tobe changed to the desired fixed output voltage TPS798xx. R1 must be shorted or removed from the EVMboard and replaced with a 0- Ωresistor. C5 must be removed and left open. Jumpers must not be installedon J6 for fixed output voltage version parts.
This section provides guidelines for the thermal management of the TPS79801DCQEM-434 board.
Thermal management is a key component of design of any power converter and is especially importantwhen the power dissipation in the LDO is high. To better help you design the TPS79801 family into yourapplication, use Equation 1 to approximate the maximum power dissipation at a particular ambienttemperature:
T
J
= T
A
+ P
d
× θ
JA
(1)
where T
J
is the junction temperature, T
A
is the ambient temperature, P
d
is the power dissipation in the IC,and θ
JA
is the thermal resistance from junction to ambient. All temperatures are in degrees Celsius.
The measured thermal resistance from junction to ambient for the TPS79801EVM has a typically value of42 °C/W. The recommended maximum operating junction temperature specified in the data sheet for theTPS79801 family is 125 °C. With these two pieces of information, the maximum power dissipation can befound by using Equation 1 .
Example Calculation:
For example, what is the maximum input voltage that can be applied to a TPS79801 with the outputvoltage configured to 3.3 V if the ambient temperature is 85 °C and the full 50 mA of load current isrequired?
Given: T
J
= 125 °C, T
A
= 85 °C, θ
JA
= 42 °C/W (2)
Using Equation 1 , substitute the preceding given values, and find that the maximum power dissipation forthe part is P
d
= 0.952 W.125 °C = 85 °C + P
d
(42 °C/W) (3)
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5 Board Layout
Board Layout www.ti.com
This means that the total power dissipation of the TPS79801 must be less than 0.952 W. Now the inputvoltage can be calculated.P
d
= (V
in
– V
out
)×I
out
= (Vin – 3.3 V) ×0.05 A = 0.952 W (4)
So, the maximum input voltage needs to be 22.3 V or less in order to maintain a safe junctiontemperature.
Similar analysis can be performed to determine the maximum input voltage at room temperature (25 °C) toprovide full output current while maintaining the junction temperature at or below 125 °C. The answerdepends on the output voltage.
Output Voltage Maximum Input Voltage
12 59.65 52.63.3 50.92.5 50.1
This section provides the TPS79801DCQEVM-434 board layout and illustrations.
Figure 1. Top Layer Assembly
4TPS79801DCQEVM-434 SLUU346 – June 2009Submit Documentation Feedback

www.ti.com Board Layout
Figure 2. Top Layer Routing
Figure 3. Bottom Layer Routing
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6 Schematic and Bill of Materials
6.1 Schematic
Schematic and Bill of Materials www.ti.com
Figure 4. Bottom Layer Assembly
This section provides the TPS79801DCQEVM-434 schematic and bill of materials.
Figure 5. TPS79801DCQEVM-434 Schematic
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6.2 Bill of Materials
www.ti.com Schematic and Bill of Materials
Table 2. TPS79801DCQEVM-434 Bill of Materials
Count RefDes Value Description Size Part Number MFR
0 C1 Open Capacitor, Ceramic 12061 C2 0.22 µF Capacitor, Ceramic, 100V, X7R, 10% 0805 STD Any1 C3 2.2 µF Capacitor, Ceramic, 50V, X7R, 10% 1206 STD Any0 C4 Open Capacitor, Ceramic 08051 C5 330pF Capacitor, Ceramic, 50V, COG, 5% 0603 STD Any4 J1-J4 PEC36SAAN Header, Male 2-pin, 100mil spacing TH PEC36SAAN Sullins1 J5 PEC36SAAN Header, Male 3-pin, 100mil spacing TH PEC36SAAN Sullins1 J6 PEC36DAAN Header, Male 2x4-pin, 100mil spacing TH PEC36DAAN Sullins1 R1 200K Resistor, Chip, 1/16W, 1% 0603 STD Any1 R2 23.2K Resistor, Chip, 1/16W, 1% 0603 STD Any1 R3 66.5K Resistor, Chip, 1/16W, 1% 0603 STD Any1 R4 124K Resistor, Chip, 1/16W, 1% 0603 STD Any1 R5 205K Resistor, Chip, 1/16W, 1% 0603 STD Any1 U1 TPS79801DCQ IC, LDO Micropower Linear Regulator, 3V-80V, 50 mA SOT223-5 TPS79801DCQ TI2 – Shunt, 100-mil, Black 0.100 3M 929950-
001 – PCB, 1.60 In ×1.500 In ×0.062 In HPA334 Any
Notes: 1. These assemblies are ESD sensitive, ESD precautions shall be observed.2. These assemblies must be clean and free from flux and all contaminants. Use of no clean flux is not acceptable.3. These assemblies must comply with workmanship standards IPC-A-610 Class 2.4. Reference designators marked with an asterisk ('**') cannot be substituted. All other components can be substituted withequivalent MFG's components.
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EVALUATION BOARD/KIT IMPORTANT NOTICE
Texas Instruments (TI) provides the enclosed product(s) under the following conditions:This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSESONLY and is not considered by TI to be a finished end-product fit for general consumer use. Persons handling the product(s) must haveelectronics training and observe good engineering practice standards. As such, the goods being provided are not intended to be completein terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety and environmentalmeasures typically found in end products that incorporate such semiconductor components or circuit boards. This evaluation board/kit doesnot fall within the scope of the European Union directives regarding electromagnetic compatibility, restricted substances (RoHS), recycling(WEEE), FCC, CE or UL, and therefore may not meet the technical requirements of these directives or other related directives.Should this evaluation board/kit not meet the specifications indicated in the User’s Guide, the board/kit may be returned within 30 days fromthe date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY SELLER TO BUYERAND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OFMERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE.The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user indemnifies TI from all claimsarising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and allappropriate precautions with regard to electrostatic discharge.EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANYINDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.TI currently deals with a variety of customers for products, and therefore our arrangement with the user is not exclusive.
TI assumes no liability for applications assistance, customer product design, software performance, or infringement of patents orservices described herein.
Please read the User’s Guide and, specifically, the Warnings and Restrictions notice in the User’s Guide prior to handling the product. Thisnotice contains important safety information about temperatures and voltages. For additional information on TI’s environmental and/orsafety programs, please contact the TI application engineer or visit www.ti.com/esh .No license is granted under any patent right or other intellectual property right of TI covering or relating to any machine, process, orcombination in which such TI products or services might be or are used.FCC Warning
This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSESONLY and is not considered by TI to be a finished end-product fit for general consumer use. It generates, uses, and can radiate radiofrequency energy and has not been tested for compliance with the limits of computing devices pursuant to part 15 of FCC rules, which aredesigned to provide reasonable protection against radio frequency interference. Operation of this equipment in other environments maycause interference with radio communications, in which case the user at his own expense will be required to take whatever measures maybe required to correct this interference.
EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the input voltage range of 3 V to 80 V and the output voltage range of 1.25 V to 32 V.Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM. If there are questionsconcerning the input range, please contact a TI field representative prior to connecting the input power.Applying loads outside of the specified output range may result in unintended operation and/or possible permanent damage to the EVM.Please consult the EVM User's Guide prior to connecting any load to the EVM output. If there is uncertainty as to the load specification,please contact a TI field representative.During normal operation, some circuit components may have case temperatures greater than 85 °C. The EVM is designed to operateproperly with certain components above 85 °C as long as the input and output ranges are maintained. These components include but arenot limited to linear regulators, switching transistors, pass transistors, and current sense resistors. These types of devices can be identifiedusing the EVM schematic located in the EVM User's Guide. When placing measurement probes near these devices during operation,please be aware that these devices may be very warm to the touch.
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