Texas Instruments | AN-1975 LMP8640 / LMP8645 Evaluation Board (Rev. C) | User Guides | Texas Instruments AN-1975 LMP8640 / LMP8645 Evaluation Board (Rev. C) User guides

Texas Instruments AN-1975 LMP8640 / LMP8645 Evaluation Board (Rev. C) User guides
User's Guide
SNOA546C – November 2009 – Revised April 2013
AN-1975 LMP8640/LMP8645 Evaluation Board
1
Introduction
This evaluation board shows a bidirectional high-side current sense made using LMP8640 (LMP8645) and
optional differential amplifier in order to have a single output.
2
Connectors
2.1
Power Supply
There are two banana plugs labeled GND and VCC to power the evaluation board. Moreover, a banana
plug labeled VCC_Amp is used to power an optional operational amplifier that makes the difference
between the outputs of the two LMP8640 (LMP8645).
2.2
Signal Connectors
There are five connectors for signals.
Table 1. Input signals
IN
It connects the non inverting input of U1 and inverting input of U2.
LOAD
It connects the non inverting input of U2 and inverting input of U1.
The device U1 is able to sense the current when it flows in the shunt resistor from the LOAD pin to the IN
pin. The device U2 is able to sense the current when it flows in the shunt resistor from IN pin to LOAD pin.
Table 2. Output signals
OUT+
Output of device U2, the voltage at this pin is related to the current that flows from the IN pin to the LOAD pin.
OUT-
Output of device U1, the voltage at this pin is related to the current that flows from the LOAD pin to the IN pin.
OUT
Optional Output of the difference amplifier that makes the difference between OUT+ and OUT-
3
Hardware Setup
3.1
Power Supply Setup
•
•
High side current sense LMP8640 (LMP8645)
– Connect a supply voltage in the range between 2.7 V and 12 V to the VCC and GND turrets.
Optional difference amplifier
– Connect a supply according to the specs of the amplifier to the VCC_Amp and GND turrets.
All trademarks are the property of their respective owners.
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
AN-1975 LMP8640/LMP8645 Evaluation Board
Copyright © 2009–2013, Texas Instruments Incorporated
1
Hardware Setup
3.2
www.ti.com
Source and Load Setup
First case: Current flows from IN to LOAD plugs.
A voltage supply can be connected between the IN and the GND banana plugs, while a load is connected
between the LOAD and the GND banana plugs. The voltage applied at the IN pin should not exceed the
maximum common mode voltage allowed by the LMP8640/HV (LMP8645/HV). The maximum allowed
common mode voltages are listed in Table 3.
Second case: Current flows from LOAD to IN plugs.
In this case, the voltage supply is connected between the LOAD and the GND banana plugs, while the
load is connected between the IN and GND banana plugs. The voltage applied at LOAD pin should not
exceed the maximum common mode voltage allowed by the LMP8640/HV (LMP8645/HV). The maximum
allowed common mode voltages are listed in Table 3.
Table 3. Max Common Mode Voltage
DEVICE
MAX VCM
LMP8640
42V
LMP8645
42V
LMP8640HV
76V
LMP8645HV
76V
According to the shunt resistor (Rsns), to the gain of LMP8640 (LMP8645) and to the supply voltage
different ranges of currents can be sensed with this evaluation board.
3.3
Components
On the evaluation board, there are already the circuit and the footprint of a standard dual op amp (U3) to
implement a differential op amp (U3.B) with reference (U3.A) in order to provide a single ended output of
the bidirectional current.
Table 4. Optional Differential Circuit
U3
Standard Dual Op Amp 8 pin.
U3.1 OUT A
U3.2 -IN A
U3.3 +IN A
U3.4 VU3.5 +IN B
U3.6 -IN B
U3.7 OUT B
U3.8 V+
R1, R2, R3, R4 resistors that implement the differential circuit according to Equation 1:
OUT = -
R4
R4 ·
* OUT + §1 +
R1
© R1 ¹
R5, R6, C5
Vref =
2
§ R2 * Vref + R3 * OUT+·
R2 + R3
© R2 + R3
¹
(1)
components for voltage reference and its filter. The voltage reference is calculating according to Equation 2:
R5
x VCC_ Amp
R5 + R6
(2)
AN-1975 LMP8640/LMP8645 Evaluation Board
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
Copyright © 2009–2013, Texas Instruments Incorporated
Using the Evaluation Board
www.ti.com
4
Using the Evaluation Board
4.1
Input and Output Signals
The evaluation board allows you to measure a bidirectional current, so the IN and LOAD banana
connectors can act either as the Source or LOAD pin. If the current flows from the IN pin to the LOAD pin,
a simple way to test the performance of the LMP8640 (LMP8645) is shown in Figure 1.
OUT
V+
V-
RG
+IN
-IN
VCC
-
V
+
DMM1
Rg1
DMM2
IN
A
+
Rsns
-IN
+IN
-
SOURCE
Rg2
+
RG
V-
V+
OUT
LOAD
ohmic
LOAD
VCC
-
Figure 1. LMP8640 (LMP8645) Measurement Setup
The DMM1 is configured as a voltmeter, which measures the output of the LMP8640 (LMP8645), while the
DMM2 is configured as an Ammeter, which measures the current that flows in the LOAD. The source is a
voltage supply that makes sure to set a voltage in the range of -2 V to +46 V for LMP8640 (LMP8645) or 2 V to +76 V for LMP8640HV (LMP8645HV).
4.2
Gain Selection of LMP8645
The evaluation board is provided with a shunt resistor Rsns (10 mΩ, @ 1%, 1W), while two gain resistors
Rg1 and Rg2 (10 kΩ, @1%) ensure a gain of 2 V/V for each current sense. The Gain is evaluated
according to formula in Equation 3:
Gain =
Rg
V/ V
5k:
(3)
The gain resistor must be chosen such that the max output voltage does not exceed the LMP8645 max
output voltage rating for a given common mode voltage (further details in the Datasheet).
4.3
Single Output
In the applications where a single measurement of a bidirectional current sense is needed is possible to
populate the evaluation board with two amplifiers and some resistors (see Section 3.3).
For instance, in the following configuration:
R1 = R2 = R3 = R4 = 10 kΩ,
R5 = R6 =10 kΩ
OUT = VREF +(OUT+ -OUT-)
VREF = 0.5*Vcc_Amp.
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
AN-1975 LMP8640/LMP8645 Evaluation Board
Copyright © 2009–2013, Texas Instruments Incorporated
3
Bill Of Materials (BOM)
www.ti.com
The VREF level represents the zero level; the voltages greater than VREF are related to a current that flows
from IN pin to the LOAD pin while the voltages less than VREF are related to a current that flows from the
LOAD pin to the IN pin. To ensure good results in the measurements, the resistors R4 and R3 and the
resistors R1 and R2 need to be well matched.
5
Bill Of Materials (BOM)
Table 5. Bill Of Materials
Designator
Component
C1, C3
Capacitor
C2, C6*
C4
,
(2)
Value
Tolerance
Package Type
0.01 μF
5%
0603
Capacitor
1 μF
10%
3216–18
Capacitor
0.1 μF
10%
0805
C5*, C7
Capacitor
0.1 μF
10%
0603
C_Filt1*, C_Filt2*
Capacitor
CG1*, CG2*
Capacitor
R1*, R2*, R3*, R4*, R5*, R6*
Resistor
min 10 kΩ
1%
0603
RG1**, RG2**
Resistor
10.0 kΩ
1%
0603
Rsns**
Resistor
0.01 Ω
1%, 1W
2010
Rsns
Resistor
0.01 Ω
0.1%, 1W
2512
R_Filt_1, R_Filt2
Resistor
5%
0805
U3*
Dual Op Amp
(1)
(2)
4
(1)
0805
0805
SOT-8
Components Marked With (*) are not soldered on the board.
Components marked with (**) are soldered only on LMP8645 board.
AN-1975 LMP8640/LMP8645 Evaluation Board
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
Copyright © 2009–2013, Texas Instruments Incorporated
www.ti.com
Appendix A Schematic
This schematic shows the evaluation board with a LMP8645 mounted on the PCB. The only difference for
the version of the PCB stuffed with LMP8640 will be the gain resistors RG1, RG2. The LMP8640 is a
current sense with fixed gain, so it doesn't require any external gain resistor.
Figure 2. Schematic Diagram
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
Copyright © 2009–2013, Texas Instruments Incorporated
Schematic
5
www.ti.com
Appendix B Layout
Figure 3. Top Layer
6
Layout
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
Copyright © 2009–2013, Texas Instruments Incorporated
Appendix B
www.ti.com
Figure 4. Bottom Layer
PCB Layout
SNOA546C – November 2009 – Revised April 2013
Submit Documentation Feedback
Copyright © 2009–2013, Texas Instruments Incorporated
Layout
7
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
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Related manuals

Download PDF

advertising