1 Introduction
This board is designed to allow the evaluation of the LP38853S-ADJ Voltage Regulator. Each board is
assembled and tested in the factory. This evaluation board has the TO-263 7-lead package mounted, and
the output voltage is set to 1.20V.
2 General Description
The LP38853 is a dual-rail adjustable LDO linear regulator capable of suppling up to 3A of output current,
and incorporates an Enable function as well as a Soft-Start function.
The device has been designed to work with 10 µF input and output ceramic capacitors, and 1µF bias
capacitor. Footprints areas for CINand C
3 Operation
User's Guide
SNVA178C–November 2006–Revised April 2013
AN-1504 LP38853S-ADJ Evaluation Board
will allow for a variety of sizes.
OUT
The input voltage, applied between VINand GND, should be at least 1.0V greater than V
than the applied V
The bias voltage, applied between V
no more than the maximum of 5.5V.
Loads can be connected to V
V
and VINtest points are provided on the board to allow accurate measurements directly onto the input
OUT
and output pins of the device, eliminating any voltage drop on the PCB traces or connecting wires to the
load.
4 Setting V
OUT
The output voltage is set using the external resistive divider R1 and R2. The output voltage is given by the
formula:
V
= V
OUT
It is recommended that the values selected for R1 and R2 are such that the parallel value is less than 10
kΩ. This is to prevent internal parasitic capacitances on the ADJ pin from interfering with the FZpole set
by R1 and CFF.
The LP38853S-ADJ Evaluation board is assembled with a 1.40 kΩ ±1% resistor for R1, and a 1.00 kΩ
±1% resistor for R2. This sets V
5 Selecting C
A capacitor placed across the gain resistor R1 will provide additional phase margin to improve load
transient response of the device. This capacitor, CFF, in parallel with R1, will form a zero in the loop
response given by the formula:
FZ= (1 / (2 × π × CFF× R1) ) (2)
The value for CFFshould be selected to set a zero frequency (FZ) between 10 kHz and 15 kHz using the
formula:
CFF= 1 / (2 × π × FZ× R1) (3)
and no greater
voltage.
BIAS
and GND should be above the minimum bias voltage of 3.0V, and
BIAS
with reference to GND.
OUT
× (1 + (R1 / R2)) (1)
ADJ
to 1.20V.
OUT
FF
OUT
All trademarks are the property of their respective owners.
SNVA178C–November 2006–Revised April 2013 AN-1504 LP38853S-ADJ Evaluation Board
Submit Documentation Feedback
1
Copyright © 2006–2013, Texas Instruments Incorporated
Enable Function
The closest standard 10% value is usually adequate for CFF.
The LP38853-ADJ Evaluation board is assembled with a 0.01 μF capacitor for CFF. This sets FZto
approximately 11.4 kHz.
Figure 1. 10mA to 3A Load Transient Response Figure 2. 1A to 3A Load Transient Response
www.ti.com
6 Enable Function
ON/OFF control is provided by supplying a logic level signal to the Enable pin. A minimum VENvalue of
1.3V is typically required at this pin to enable the LDO output. The LDO output will be shutdown when the
VENvalue is typically 1.0V or less. The VENthreshold incorporates approximately 100mV of hysteresis.
In applications where the LP38853 is operated continuously the Enable pin can be connected directly to
V
, or left open. The Enable pin has a 200 kΩ internal resistor to V
BIAS
care should be taken to minimize any capacitance on the Enable pin, as any capacitance will introduce an
RC delay time on the Enable function.
. If the Enable pin is left open,
BIAS
2
AN-1504 LP38853S-ADJ Evaluation Board SNVA178C–November 2006–Revised April 2013
Figure 3. Enable Thresholds
Copyright © 2006–2013, Texas Instruments Incorporated
Submit Documentation Feedback
www.ti.com
7 Soft-Start Function
V
will rise at an RC rate defined by the internal resistance of the SS pin (rSS), and the external capacitor
REF
(CSS) connected to the SS pin. This allows the output voltage to rise in a controlled manner until steadystate regulation is achieved. Typically, five time constants are recommended to assure that the output
voltage is sufficiently close to the final steady-state value. During the soft-start time the output current can
rise to the built-in current limit.
The LP38853S-ADJ Evaluation board is assembled with a 0.01 μF capacitor for CSS. This sets the softstart time to approximately 750 μs.
Soft-Start Function
8 Power Dissipation
The TO-263 package alone has a junction to ambient thermal resistance (θJA) rating of 60°C/W. When
mounted on the LP38853S evaluation board the θJArating is approximately 40°C/W.
Although there is only approximately 0.30 square inches of 1 ounce copper area immediately under the
tab, the top copper surface area is extended to additional copper area on the bottom of the board by nine
thermal vias.
With the 40°C/W thermal rating the LP38853S-ADJ evaluation board will dissipate a maximum of 2.5W
with TA= 25°C.
Figure 4. V
Soft-Start
OUT
Figure 5. Maximum Power Dissipation vs Ambient Temperature
SNVA178C–November 2006–Revised April 2013 AN-1504 LP38853S-ADJ Evaluation Board
Submit Documentation Feedback
3
Copyright © 2006–2013, Texas Instruments Incorporated
IN (3)
BIAS (7)
GND (4)
(6) OUT
V
OUT
(J6)VIN (J3)
V
BIAS
(J7)
C
IN
10 PF
C
OUT
10 PF
C
BIAS
1 PF
GND (J4)
LP38853S-ADJ
(5) ADJ
R1
1.40 k:
R2
1.00 k:
C
FF
0.01 PF
VEN (J2)
SS (1)
C
SS
0.01 PF
EN (2)
TP3 TP7 TP2 TP1 TP4 TP5 TP6
TAB
IS
GND
LP38853S-ADJ
BIAS
OUT
GND
SS 1
2
3
4
5
IN
6
7
ADJ
EN
Pin Out
9 Pin Out
10 Schematic Diagram
www.ti.com
Figure 6. Pin Out
4
AN-1504 LP38853S-ADJ Evaluation Board SNVA178C–November 2006–Revised April 2013
Figure 7. Evaluation Board Schematic.
Copyright © 2006–2013, Texas Instruments Incorporated
Submit Documentation Feedback
R1
1.40 k:
R2
1.00 k:
V
BIAS
V
OUT
TP3
TP4
TP6
TP5
TP2
TP1
TP7
C5
C4 R1
R2
C2
C1
C3
VIN
EN
VOUT
BIAS
GND
U1
LP38853S
-ADJ
C
BIAS
(C2)
1 PF
C
IN
(C1)
10 PF
C
OUT
(C3)
10 PF
CSS (C5)
0.01 PF
CFF (C4)
0.01 PF
J2
J3
J4
J6
GND
V
IN
V
EN
J7
www.ti.com
11 PCB Layout
PCB Layout
Figure 8. Evaluation Board Component and Pin Layout
SNVA178C–November 2006–Revised April 2013 AN-1504 LP38853S-ADJ Evaluation Board
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
5
Bill of Materials
12 Bill of Materials
ID Name Description Manufacturer Part Number
U1 U1 LP38853 Texas Instruments LP38853
C1 C
C2 C
C3 C
C4 C
C5 C
J2 V
J3 V
J4 GND Johnson Components 108-0903-001
J6 V
J7 V
R1 R1 CRCW 0805 1401 F
R2 R2
TP1 TP
TP2 TP
TP3 TP
TP4 TP
TP5 TP
TP6 TP
TP7 TP
BIAS
OUT
FF
SS
EN
IN
OUT
BIAS
GND
OUT
BIAS
IN
SS
EN
ADJ
www.ti.com
Capacitor: 10 µF; ±10%; MLCC; 10V;
X7R; 1210
Capacitor: 1 µF;, ±10%; MLCC; 10V;
X7R; 0805
Capacitor: 10 µF;, ±10%; MLCC; 10V;
X7R; 1210
Capacitor: 0.01 µF;, ±10%; MLCC;
10V; X7R; 0805
Capacitor: 0.01 µF; ±10%;, MLCC;
10V; X7R; 0805
Banana Jack : Insulated Solder
Terminal; White
Banana Jack : Insulated Solder
Terminal; Red
AVX 1210ZC106KAT2A
1210ZC106KAT2A
0805ZC105KAT2A
0805YC103KAT2A
0805YC103KAT2A
108-0901-001
108-0902-001
Banana Jack : Insulated Solder
Terminal; Black
Banana Jack : Insulated Solder
Terminal; Orange
Banana Jack : Insulated Solder
Terminal; Blue
108-0906-001
108-0910-001
Resistor: 1.40 kΩ, ±1%; Thick Film;
250 mW; ±100 ppm; 0805
Resistor: 1.00 kΩ, ±1%; Thick Film; CRCW 0805 1001 F
VISHAY DALE
250 mW; ±100 ppm; 0805
IN
Turret Terminal : Mounting Hole
Diameter = 0.062”
Keystone 1593–2
6
AN-1504 LP38853S-ADJ Evaluation Board SNVA178C–November 2006–Revised April 2013
Copyright © 2006–2013, Texas Instruments Incorporated
Submit Documentation Feedback
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products Applications
Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive
Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications
Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers
DLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps
DSP dsp.ti.com Energy and Lighting www.ti.com/energy
Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial
Interface interface.ti.com Medical www.ti.com/medical
Logic logic.ti.com Security www.ti.com/security
Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense
Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video
RFID www.ti-rfid.com
OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com
Wireless Connectivity www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2013, Texas Instruments Incorporated
Loading...