User’s Guide
ROHM Solution Simulator
Low Noise, Low Input Offset Voltage CMOS Operational Amplifiers (Op Amps)

Low-Side Current Sensing Circuit– DC Sweep simulation
This circuit simulates DC sweep response at the low-side current sensing with Op Amps. You can observe the output voltage
and the ratio of output to input voltage or shunt voltage when the source or load current is changed. You can customize theparameters of the components shown in blue, such as VIN, or peripheral components, and simulate the low-side current
sensing circuit with the desired operating condition.
You can simulate the circuit in the published application note: Low-Side Current Sensing Circuit Design. [JP] [EN] [CN]General Cautions
Caution 1: The values from the simulation results are not guaranteed. Please use these results as a guide for your design.
Caution 2: These model characteristics are specifically at Ta=25°C. Thus, the simulation result with temperature variances
may significantly differ from the result with the one done at actual application board (actual measurement).
Caution 3: Please refer to the Application note of Op Amps for details of the technical information.
Caution 4: The characteristics may change depending on the actual board design and ROHM strongly recommend todouble check those characteristics with actual board where the chips will be mounted on.

1Simulation Schematic

ISOURCEVSOURCE2VIN
VSOURCE1

VOFigure 1. Simulation Schematic

2

How to simulate
The simulation settings, such as parameter sweep or convergence options,are configurable from the ‘Simulation Settings’ shown in Figure 2, and Table
1 shows the default setup of the simulation.

SimulationSettings

In case of simulation convergence issue, you can change advanced
options to solve. Nothing is stated in the default statement in ‘ManualOptions’. You can modify it.

Simulate

Figure 2. Simulation Settings and execution
Table 1. Simulation settings default setup
Parameters
Default
DCSimulation TypeISOURCE
Parameter Sweep
Balanced
Advanced options
Convergence Assist
Manual Options-Note
Do not change Simulation TypeCURRENT_LEVEL from 5A to 100A by 1A-No. 64UG046E Rev.001
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Low-Side Current Sensing Circuit – DC Sweep simulation
3Simulation Conditions
Table 2. List of the simulation condition parameters
InstanceTypeParameters
Name
Voltage_level
VSOURCE1
Voltage Source
AC_magnitude
AC_phase
Voltage_level
Voltage Source
VSOURCE2
AC_magnitude
For Op Amp
AC_phase
Current_level
ISOURCE

Current Source

AC_magnitude
AC_phase(Note 1) Set it to the guaranteed operating range of the Op Amps.

4

User’s Guide

Default
Value
120.00.0
50.00.0
50.00.0

Variable Range
MinMax
free
fixed
fixed
free(Note1)
fixed
fixed
free, for parameter
sweep
fixed
fixedUnits
VV°
VV°
AA°

Op Amp model
Table 3 shows the model terminal function implemented. Note that LMR1802G-LB is the behavior model for its low-sidecurrent sensing circuit, and no protection circuits or the functions not related to the purpose are not implemented.
Table 3. LMR1802G-LB model terminals used for the simulation
Terminals
Description
Non-inverting input+IN
Inverting input-IN
Positive power supply
VDD
Negative power supply / Ground
VSS
OutputOUT(Note 2) This model is not compatible with the influence of ambient temperature.
(Note 3) Use the simulation results only as a design guide and the data reported herein is not a guaranteed value.

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User’s Guide

Low-Side Current Sensing Circuit – DC Sweep simulation
5Peripheral Components
5.1 Bill of Material
Table 4 shows the list of components used in the simulation schematic. Each of the capacitors has the parametersof equivalent circuit shown below. The default values of equivalent components are set to zero except for the ESR ofC. You can modify the values of each component.
Table 4. List of capacitors used in the simulation circuit
TypeResistor
Capacitor

Instance NameDefault ValueRSHUNT
R11, R12R21, R22
C11, C121m2120
150

Variable Range
MinMax0.1m1
freefreefreeUnitsΩkΩkΩ
pF

5.2 Capacitor Equivalent Circuits(a) Property editor(b) Equivalent circuit
Figure 3. Capacitor property editor and equivalent circuit
The default value of ESR is 0.01Ω.
(Note 4) These parameters can take any positive value or zero in simulation but it does not guarantee the operationof the IC in any condition. Refer to the datasheet to determine adequate value of parameters.

6Recommended Products
6.1

Op Amp
LMR1802G-LB : Low Noise, Low Input Offset Voltage CMOS Operational Amplifier. [JP] [EN] [CN]6.2

Shunt resistor
PSR100 Series : High Power Ultra-low Ohmic Shunt Resistors [JP] [EN] [CN]Technical Articles and Tools can be found in the Design Resources on the product web page.

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NoticeNotes
1) The information contained herein is subject to change without notice.
2) Before you use our Products, please contact our sales representative and verify the latest specifications :3) Although ROHM is continuously working to improve product reliability and quality, semiconductors can break down and malfunction due to various factors.
Therefore, in order to prevent personal injury or fire arising from failure, please take safetymeasures such as complying with the derating characteristics, implementing redundant andfire prevention designs, and utilizing backups and fail-safe procedures. ROHM shall have noresponsibility for any damages arising out of the use of our Poducts beyond the rating specified byROHM.
4) Examples of application circuits, circuit constants and any other information contained herein areprovided only to illustrate the standard usage and operations of the Products. The peripheral
conditions must be taken into account when designing circuits for mass production.
5) The technical information specified herein is intended only to show the typical functions of andexamples of application circuits for the Products. ROHM does not grant you, explicitly or implicitly,
any license to use or exercise intellectual property or other rights held by ROHM or any otherparties. ROHM shall have no responsibility whatsoever for any dispute arising out of the use ofsuch technical information.
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