Texas Instruments OPA462EVM User manual

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OPA462EVM
User's Guide
SBOU175–October 2019
OPA462EVM
This user's guide describes the characteristics, operation, and use of the evaluation module (EVM) for the
OPA462. The EVM is designed to evaluate the performance of the devices in both single and dual-supply
configurations. This document also includes the schematic, printed circuit board (PCB) layout, and a bill of
materials (BOM). Throughout this document the terms evaluation board,evaluation module, and EVM are
synonymous with OPA462EVM.
WARNING
Danger: HIGH VOLTAGE! This evaluation board is intended for
professional use only. It has exposed high voltages. Do not
operate this board without proper high-voltage/high-current safety
practices. Read Section 1.4 before using the EVM.

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OPA462EVM
Contents
1 Overview ..................................................................................................................... 3
1.1 OPA462.............................................................................................................. 3
1.2 OPA462EVM ........................................................................................................ 3
1.3 Related Documentation............................................................................................ 3
1.4 Evaluation Module Limitations and Cautions.................................................................... 3
2 Getting Started............................................................................................................... 4
2.1 Power Supplies ..................................................................................................... 4
2.2 Jumpers.............................................................................................................. 4
2.3 Inputs................................................................................................................. 4
2.4 Outputs............................................................................................................... 4
2.5 Enable or Disable (E/D)............................................................................................ 4
2.6 Status Flag........................................................................................................... 5
3 Application Circuits .......................................................................................................... 6
3.1 Improved Howland Current Pump................................................................................ 6
4 Schematic, PCB Layout, and Bill of Materials ........................................................................... 9
4.1 EVM Schematic..................................................................................................... 9
4.2 EVM Default Configuration....................................................................................... 10
4.3 PCB Layout ........................................................................................................ 11
4.4 Bill of Materials .................................................................................................... 12
List of Figures
1 Practical, 20-mA, Improved Howland Current-Pump Circuit........................................................... 6
2 Improved Howland Current Pump Output-Voltage Compliance Range .............................................. 7
3 Improved Howland Current Pump Applied as a Peak AC-Current Generator....................................... 8
4 OPA462EVM Schematic.................................................................................................... 9
5 OPA462EVM Default Configuration ..................................................................................... 10
6 OPA462EVM PCB Layout ................................................................................................ 11
List of Tables
1 Related Documentation..................................................................................................... 3
2 Jumper Table................................................................................................................. 4
3 OPA462EVM BOM......................................................................................................... 12
Trademarks
PowerPAD is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.

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OPA462EVM
1 Overview
1.1 OPA462
The OPA462 is a precision power amplifier capable of operating over a very wide supply range of ±6 V to
±90 V, with an input common-mode range that extends to within a few volts from each rail. This amplifier
is composed of an internal differential input amplifier stage, followed by a voltage amplifier, and finally, a
high-current output stage. This device is designed to avoid phase inversion problems that are typically
found in similar op amps. The OPA462 is unity-gain stable, and comes in an SO PowerPAD™ package.
1.2 OPA462EVM
The OPA462EVM is intended to provide basic functional evaluation of the OPA462. The EVM provides the
following features:
• Easy access to pertinent nodes with test points and terminal blocks
• Convenient input and output filtering
• Access to multiple nodes and footprints for compensation
• Protection against power supply sequencing and inductive load kickback
• Configurable for any common amplifier topology, including the improved Howland current pump
• Footprints for providing a flexible reference voltage
1.3 Related Documentation
The following documents listed in Table 1 provide information about TI's integrated circuits and support
tools for the OPA462EVM.
Table 1. Related Documentation
Document Literature Number
OPA462 Product Data Sheet SBOS803
OPA445 Product Data Sheet SBOS156
1.4 Evaluation Module Limitations and Cautions
As a result of the high common-mode input voltage rating of the OPA462, evaluation of the device often
involves high-voltage operation. As a difference amplifier, it may also be used in current-sensing
applications. In addition to voltage and current limitations, proper electrostatic discharge precautions are
recommended.
1.4.1 High Voltage Warning
The OPA462 is rated for supply voltages up to ±90 V (180 V for single supply), and common-mode input
voltages up to ±85 V. When using the device and EVM under such circumstances, all proper safety
practices must be followed. Do not apply more than rated voltages. See the OPA462 data sheet for
additional information.
1.4.2 Electrostatic Discharge Caution
Many of the components on the OPA462EVM are susceptible to damage by electrostatic discharge (ESD).
Customers are advised to observe proper ESD handling precautions when unpacking and handling the
EVM, including the use of a grounded wrist strap at an approved ESD workstation.
CAUTION
A wrist strap may only be used with circuit voltages less than 100 V. For circuit
voltages equal to or greater than 100 V, use an ionizer.

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OPA462EVM
2 Getting Started
This section explains the connectors and jumpers, and details the basic EVM functionality.
2.1 Power Supplies
The OPA462EVM can be configured from ±6 V to ±90 V for dual supply operation, or from 12 V to 180 V
for single-supply operation. Shorting pins 2 and 3 of J5 sets the EVM to single supply, and shorting pins 1
and 2 of J5 sets up the EVM for dual supplies. The OPA462 is capable of sourcing or sinking up to 30 mA
of current. Power is provided to the EVM through J2 (V+) and J1 (V–). Take care to select supplies
capable of providing the required power for the application. Use a supply capable of supplying at least
twice the anticipated current at the intended operating voltage.
2.2 Jumpers
There are six jumpers located on the OPA462EVM. The jumper functions are summarized in Table 2.
Table 2. Jumper Table
Jumper Function
J3 Enable or disable (E/D) common configuration
J4 Enable or disable (internal or external)
J5 Sets the negative supply to GND for single-supply operation.
J7 Selects inverting input (external or GND)
J10 Selects noninverting input (external or GND)
J12 Sets the reference voltage at the noninverting pin
2.3 Inputs
The inputs to the EVM can be any signal within the common-mode voltage range. BNC connectors are
available at both inputs to allow for easy interfacing with signal generators or other equipment.
Additionally, signals can be input using test points TP12 (IN–) and TP14 (IN+).
Jumpers J7 and J10 set the voltages seen at IN– and IN+, respectively. Short pins 2 and 3 of these
jumpers to set the inputs to GND. Short pins 1 and 2 to allow whatever voltages present at the input BNCs
to be passed to the op amp.
2.4 Outputs
The output of the EVM can be monitored from TP13. A BNC connector, J8, and terminal block, J11, are
also provided to interface with other equipment or circuits. The EVM includes footprints for a load resistor,
load capacitor, and an RC snubber network. If significant power is going to be driven into the load, use
external loads.
2.5 Enable or Disable (E/D)
The OPA462 incorporates a disable feature that can be set using jumpers J3 and J4 on the EVM. The
disable is accomplished without disturbing the input signal path, which helps save power in addition to
protecting the load. Jumper J3 sets the voltage of the E/D Com pin, which can be set to either the
negative rail or GND. The voltage at the E/D Com pin serves as the reference voltage for the E/D pin. J4
sets the voltage at the E/D pin. The device is enabled by floating the E/D pin, or by forcing the E/D pin
high using an external voltage. If forcing the E/D pin high, the pin must be pulled at least 2.5 V greater
than the E/D Com pin, but should not be pulled any more than 5 V greater than the E/D Com pin. Shorting
the E/D pin to the E/D Com pin disables the device.

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OPA462EVM
2.6 Status Flag
The OPA462 incorporates a status flag pin to indicate overcurrent or overtemperature conditions. This pin
is an open-drain, active-low output that allows the pin to be easily interfaced with standard low-voltage
logic. The pin goes active if the junction temperature of the device rises to greater than 150°C, and resets
after the device cools to 130°C. Additionally, the pin goes active if the device attempts to source more
than the maximum continuous current of 30 mA. The status flag can be monitored from TP2, and an
external pullup voltage can be input on TP11.
2.6.1 Circuit Protection
The OPA462EVM is protected from inductive surges and power supply transients with the use of
Schottkey diodes on the amplifier output and transient voltage suppressors on the power supply inputs.
See D1, D2, D3 and D4 on the schematic shown in Figure 4, and in the BOM shown in Table 3 at the end
of this document.
In addition, footprints have been provided for optional components Q1 and Q2. These may be used to
protect the amplifier inputs from voltage transients that briefly exceed the maximum input voltage. See the
BOM at the end of this document for the recommended part number.

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OPA462EVM
3 Application Circuits
The OPA462EVM may be configured in most standard op amp circuits. See the OPA462 data sheet for
typical applications.
3.1 Improved Howland Current Pump
The OPA462EVM can be configured as an improved Howland current pump that provides an output
current proportional to a single- or differential-input voltage. The improved Howland current pump is
described and analyzed in section 3 of the A Comprehensive Study of the Howland Current Pump
application report. Information about how the current-pump resistor values are determined for a particular
input voltage and a corresponding output current is provided in the application report. The report
information is applied here in this section as a practical use for the OPA462EVM.
The OPA462EVM, as configured in Figure 1, sources on an output current of –20 mA when a single-
ended input voltage of 2.5 V is applied to the VP input. If the input voltage sign is reversed, the output
reverses direction and sinks 20 mA. The circuit in Figure 1 provides the resistance values required to
obtain the correct 20-mA output current. The resistor and capacitor labels correspond to those screened
on the OPA462EVM printed circuit board. As shown in Figure 1, when RL is equal to 500 Ω, the sourced
output current level is –20 mA, and Vout is 10 V, as Ohm’s law dictates.
Figure 1. Practical, 20-mA, Improved Howland Current-Pump Circuit
Practical current sources have a limited output voltage range that can be covered. The OPA462 op amp
has a wide output voltage range because of the high-voltage supplies used. The OPA462 data sheet
provides information about the linear output voltage range that should always be observed.

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OPA462EVM
For the improved Howland current pump application, the output voltage (Vout) that is attainable at the load
is further constrained by the voltage drop developed across Rhcp. The 20-mA load current flows through
the resistor, and causes a voltage drop. Therefore, with a fixed 20-mA output current flowing through RL,
there is a limit as to how far Vout can swing. For this example, the limit occurs when Vout reaches
approximately 57.4 V, and RL is 2.87 kΩ. This limit can be seen in Figure 2. Resistor RL can be any value
from 0 Ωto 2.87 kΩ, and the output will remain within the circuit linear compliance range. However, if the
value of RL is increased further, the current pump operation is forced outside the compliance range, and
the output current will no longer remain constant. Thus, increasing the value of RL to greater than 2.87 kΩ
defeats the goal of providing a constant current.
Figure 2. Improved Howland Current Pump Output-Voltage Compliance Range
The improved Howland current pump can be used to generate an ac waveform with a peak current that
corresponds to a maximum specified dc value. A 20-mA dc current source using the OPA462 has been
demonstrated, and will now be used to show how a 20-mA peak ac-current waveform can be realized.

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OPA462EVM
The same circuit shown in Figure 1 is applied, except the 2.5-VDC VP voltage source in Figure 1 is
replaced by an 100-Hz ac source having a peak voltage of 2.5 V. The peak output current depends on the
peak voltage level applied at the VP input. A triangle wave is used in the example; however, a sine wave,
square wave, or other waveform could be applied instead. Figure 3 shows that a 2.5-V peak input triangle
wave applied to the current pump input, VP, results in a 20-mA peak triangle wave at the output, Vout.
Figure 3. Improved Howland Current Pump Applied as a Peak AC-Current Generator
The improved Howland current pump op amp circuit relies on both negative and positive feedback for
operation; more negative feedback than positive feedback, but that feedback does not always provide
stability. When unity-gain-stable op amps, such as the OPA462, are employed and they drive a resistive
load, the op amp phase margin should be sufficient such that the circuit is stable. However, if the output
load is complex, containing both resistive and reactive components (R±jX), there can be combinations that
degrade the phase margin, and instability results. Degradation of the phase margin often occurs when the
current pump is used to drive loads that are predominantly inductive.
The OPA462EVM has a number of positions where component may be added to stabilize the various
OPA462 amplifier and improved Howland current pump configurations that are supported by the EVM.
Some of the component locations that are used for this purpose are R6 (ISO), R5 (Rng), C12 (Cng, noise
gain), R10 (Rsn), C16 (Csn, snubber), and C9 and C10 in the feedback loop. Compensation, when
required, is determined based on the particular circuit to which the OPA462 is being applied. Op amp
stability and compensation is a vast subject covered in numerous TI documents, and TI training programs
such as TI Precision Labs – Op Amps.

GND
TP1
V+
TP9
0.1uF
C1
0.1uF
C4
TP3 TP4
V+
GND
R9RL
TP13
V+
E/D
E/D Com
E/D Com
GND
E/D
Op Amp Supplies and Bulk Decoupling
TP10
E/D EXT
GND
0.1uF
C7
Enable/Disable Configuration
1 2 3
J4
R12 Rref
TP15
VREF Ext
10k
R4
GND
GND
1 2 3
J12
VREF Select
GND
SF
1 2 3
J3
V-
SF Pull-Up
SF
GND
R11
Rf+
1
2
3
J7
-In Select
TP12
TP14
1
2
3
J10
+In Select
GND
R10
Rsn
1 2 3
J5
GND
0.1uF
C15
GND
0.1uF
C11
GND
1
2
J11
Vout
GND
R5 Rng
GND
GND
GND
GND
0
R8
0
R6 Riso
0
R7 Rhcp
TP5 TP6
V-
V-
TP2
SF
C13
CL
C16
Csn
Power Supply
Minimum: 12V (+/-6V)
Maximum: 180V (+/-90V)
TP11
SF EXT
GND
0.1uF
C8
TP16
GND
TPTT 1
V+
TPTT 9
0.1uF
C1
0.1uF
C4
TPTT 3 TPTT 4
V+
1 2 3
J5
GND
TPTT 5 TPTT 6
V-
Poweww r Supply
Minimum: 12V (+/-6V)
Maxixx mum: 180V (+/-90V)
TPTT 16
E/D Com
GND
E/D
TPTT 10
E/D EXT
GND
0.1uF
C7
1 2 3
J4
1 2 3
J3
V-
SF
TPTT 2
SF TTPTT 11
SF EXT
GND
0.1uF
C8
p
D3
D4
V+
V-
23
1,8
Q1A
6 7
4,5
Q2B
A
B
C
D
C
D
2 3
1,8
Q2A
67
4,5
Q1B
C
D
A
B
Input Protection
23
1,8
Q1A
6 7
4,5
Q2QQ B
2 3
1,8
Q2QQ A
67
4,5
Q1B
Input Protection
0
R13
0
R1
100k
R3
E/D Com
10uF
C2
10uF
C3
10uF
C5
10uF
C6
1
2
J1
1
2
J2
2
1
3
4
5
V+
V-
6
8 7
9
OPA462IDDAR
U1
100k
R2
Ext
GND
GND
Ext
Int Ext
90V
D1
90V
D2
C9
C10
C12 Cng
C14
C17
C18
1
2
3
4
5
J6
-In
1
2
3
4
5
J9
+In
1
2
3
4
5
J8
Vout
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OPA462EVM
4 Schematic, PCB Layout, and Bill of Materials
This section discusses the OPA462EVM hardware schematics, PCB layout and jumper configurations.
4.1 EVM Schematic
Figure 4 depicts the complete OPA46xEVM schematic.
Figure 4. OPA462EVM Schematic

GND
TP1
V+
TP9
0.1uF
C1
0.1uF
C4
TP3 TP4
V+
TP13
V+
E/D
E/D Com
E/D Com
GND
E/D
Op Amp Supplies and Bulk Decoupling
TP10
E/D EXT
Enable/Disable Configuration
1 2 3
J4
10k
R4
GND
SF
1 2 3
J3
V-
SF Pull-Up
SF
1
2
3
J7
-In Select
TP12
TP14
1
2
3
J10
+In Select
GND
1 2 3
J5
GND
0.1uF
C15
GND
0.1uF
C11
GND
1
2
J11
Vout
GND
GND
GND
GND
0
R8
R6
Riso
R7
Rhcp
TP5 TP6
V-
V-
TP2
SF
Power Supply
Minimum: 12V (+/-6V)
Maximum: 180V (+/-90V)
TP11
SF EXT
GND
0.1uF
C8
TP16
D3
D4
V+
V-
100k
R3
E/D Com
J8
Vout
J6
-In
J9
+In
10uF
C2
10uF
C3
10uF
C5
10uF
C6
1
2
J1
1
2
J2
2
1
3
4
5
V+
V-
6
8 7
9
OPA462IDDAR
U1
100k
R2
Ext
GND
GND
Ext
90V
D1
90V
D2
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4.2 EVM Default Configuration
The OPA462EVM ships in a standard amplifier configuration with a noninverting gain of 11. Figure 5 shows the schematic for the default
configuration. Any components shown on the complete schematic but not on this schematic are optional and not installed.
Figure 5. OPA462EVM Default Configuration

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4.3 PCB Layout
Figure 6 depicts the PCB layout.
Figure 6. OPA462EVM PCB Layout
NOTE: Board layout is not to scale. This figure is intended to show how the board is laid out, and is
not intended to be used for manufacturing OPA462EVM PCBs.

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4.4 Bill of Materials
Table 3 lists the bill of materials (BOM) used for the OPA46xEVM.
Table 3. OPA462EVM BOM
Designator Quantity Description Part Number Manufacturer Notes
C1, C4, C11, C15 4 CAP, CERM, 0.1 uF, 450 V, +/- 10%, X7T, 1206_190 C3216X7T2W104K160AA TDK
C2, C3, C5, C6 4 CAP, AL, 10 uF, 250 V, +/- 20%, SMD ULR2E100MNL1GS Nichicon
C8 1 CAP, CERM, 0.1 uF, 25 V, +/- 10%, X7R, 0603 06033C104KAT2A AVX
D1, D2 2 Diode, TVS, Uni, 90 V, 146 Vc, SMC 5.0SMDJ90A Littelfuse
D3, D4 2 Diode, Ultrafast, 400 V, 1 A, SMB MURS140-13-F Diodes Inc.
H1, H2, H3, H4 4 MACHINE SCREW PAN PHILLIPS 4-40 9900 Keystone
H5, H6, H7, H8 4 2203 Keystone
J1, J2, J11 3 Terminal Block, 2x1, 6.35mm, Green, TH 1714955 Phoenix Contact
J3, J4, J5, J7, J10,
J12 6Header, 2.54mm, 3x1, Tin, TH 68001-403HLF FCI
J6, J8, J9 3 BNC Low Profile Elbow Jack, Gold, R/A, TH 5-1634513-1 TE Connectivity
R1, R8, R13 3 RES, 0, 5%, 0.1 W, 0603 RC0603JR-070RL Yageo
R2, R3 2 RES, 100 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603 CRCW0603100KFKEA Vishay-Dale
R4 1 RES, 10.0 k, 0.1%, 0.1 W, 0603 RG1608P-103-B-T5 Susumu Co Ltd
R6, R7 2 RES, 0, 5%, 1 W, 2512 RC6432J000CS Samsung
SH-J1, SH-J2, SH-J3,
SH-J4, SH-J5, SH-J6 6Shunt, 100mil, Gold plated, Black 881545-2 TE Connectivity
TP1, TP2, TP3, TP4,
TP5, TP6, TP9, TP10,
TP11, TP12, TP13,
TP14, TP15, TP16 14 Test Point, Compact, SMT 5016 Keystone
U1 1High-Voltage (180-V), High-Current (30-mA) Operational
Amplifier, G = 1 Stable, DDA0008J (SOIC-8) OPA462IDDAR Texas Instruments OPA462IDDA
C7 0 06033C104KAT2A AVX Optional-Not installed
C9, C10, C12, C14,
C17, C18 0Optional-Not installed
C13, C16 0 Optional-Not installed
FID1, FID2, FID3 0 Optional-Not installed
Q1, Q2 0 JFET, 2-CH, N-CH, V, A, SOIC-8 IF1322A InterFET Optional-Not installed
R5, R11, R12 0 Optional-Not installed
R9, R10 0 Optional-Not installed

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