User’s Guide
ROHM Solution Simulator
3.5V to 40V Input, 2A Single 2.2MHz Buck DC/DC Converter for Automotive

BD9P235MUF-C / Line Response
This circuit simulate the line response of BD9P235MUF-C. You can observe the fluctuation of the output voltage when theload current is abruptly changed. You can customize the parameters of the components shown in blue, such as VIN, IOUT, orperipheral components, and simulate the Line response with desired operating condition.

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 datasheet for details of the technical information
Caution 4: The characteristics may change depending on the actual board design and ROHM strongly recommend to
double check those characteristics with actual board where the chips will be mounted on.

1

Simulation Schematic

VOUTVIN

Figure 1. Simulation Schematic2

How to simulate
The simulation settings, such as simulation time or convergence options, are configurable from the ‘Simulation Settings’
shown in Figure 2, and Table 1 shows the default setup of the simulation.
In case of simulation convergence issue, you can change advanced
options to solve. Default statement in ‘Manual Options’ sets the time to startsaving the result to 1.2ms. You can modify or delete it.

Simulation
Settings
Simulate

Figure 2. Simulation Settings and execution
Table 1. Simulation settings default setup
Parameters
Default
Time-Domain
Simulation Type3ms
End Time
Balanced
Advanced options
Convergence Assist“.tran 0 3m 1.2m”
Manual Options

Note
Do not change Simulation TypeNo. 63UG123E Rev.001
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BD9P235MUF-C Line Response
3

Simulation Conditions
Table 2. List of the simulation condition parameters
Instance
TypeParameters
Name
VBAT
Voltage Source
Initial_value
Pulse_value
ramptime_initial_to_pulse
ramptime_pulse_to_initial
Start_delay
Pulse_width
PeriodVEN
Voltage Source
Pulse_value

Default
Value
1681010
1.5
1.0
3.016

Variable Range
MinMax
3.540
3.540
No constraint(Note1)
No constraint(Note1)
Use the same value as thevoltage_level of VBATVOCP_SEL Voltage Source
voltage_level
00: Max output current =2A,or 5: Max output current=1.5A
VMODE
Voltage Source
voltage_level
50: Auto mode,or 5: FPWM mode
IOUT
Current source
Current_level202(Note 1) This is a constraint of the simulation settings and does not guarantee the operation of the IC.

UnitsVV
µs
µs
msms
ms
VVVA

3.1 VBAT parameter setup
Figure 3 shows how the VBAT parameters correspond to the VIN stimulus waveform.
Initial_value
Start_delay

Period(to the next falling edge)

VIN*0.2ms of soft start period
Waveforms recorded
from t=1.2ms
Pulse_value

VOUT(a) Overall view
Pulse_width

VIN
Ramptime_initial_to_pulse

Ramptime_pulse_to_initial

VOUT(b) Magnified view
Figure 3.VIN parameters and its waveform

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User’s Guide

BD9P235MUF-C Line Response4BD9P235MUF-C_Tran model
Table 3 and Table 4 shows the model terminal function implemented. Note that BD9P235MUF-C_Tran is the behavior
model for its load/line response operation, and no protection circuits or the functions not related to the purpose are not
implemented.
Table 3. BD9P235MUF-C_Tran model terminals used for the simulation
Terminals
Description
Enable input
EN
Power supply input
VIN
Power supply input
PVIN
Power ground
PGND
Switching node
SW
Over current selector input
OCP_SEL
PWM mode selector input
MODEGround
GND
Phase compensation.
VOUT_SNS
3.3V output for internal circuit.
VREG
Table 4. BD9P235MUF-C_Tran model terminals NOT used for the simulation
Terminals
Description
Input is ignored (always enable)
EN
Input is ignored (Bootstrap not implemented)
BST
Input is ignored (SSCG not implemented)
SSCG
The function is not implemented
RESET
Input is ignored
VOUT_DIS
Input is ignored (function not implemented)
VCC_EX(Note 2) This model is not compatible with the influence of ambient temperature.
(Note 3) This model is not compatible with the external synchronization function.
(Note 4) Use the simulation results only as a design guide and the data reported herein is not a guaranteed value.

4.1

Parameter TSS
BD9P235MUF-C_Tran model has the property ‘TSS’, which is the soft start time described in page 7 of thedatasheet. The product has 3ms (typical) of the startup time of the output voltage. You can short cut the soft start bychanging TSS value. The default TSS value is set to 0.2ms in this simulation and you can modify the value in theproperty editor.

Figure 4. TSS property of BD9P235MUF-C_Tran

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BD9P235MUF-C Line Response

5Peripheral Components
5.1 Bill of Material
Table 5 shows the list of components used in the simulation schematic. Each of the capacitor and inductor has theparameters of equivalent circuit shown below. The default value of equivalent components are set to zero except forthe parallel resistance of L1. You can modify the values of each component.
Table 5. List of capacitors used in the simulation circuit
TypeInstance NameDefault Value
Capacitor
CBLK
220
CIN1
0.1
CIN2
4.7
CREG
1.0
COUT122
COUT222Inductor
L1
3.3

Units
µF
µFµFµFµFµFµH

5.2 Capacitor Equivalent Circuits(a) Property editor(b) Equivalent circuit
Figure 5. Capacitor property editor and equivalent circuit
5.3 Inductor Equivalent Circuits(a) Property editor(b) Equivalent circuit
Figure 6. Inductor property editor and equivalent circuit
The default value of PAR_RES is 6.6kohm.
(Note 5) 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.

6Link to the product information and tools
6.1

Product webpage link:
https://www.rohm.com/products/power-management/switching-regulators/integrated-fet/buck-converters-synchron
ous/bd9p235muf-c-product

6.2

Related documents
The application notes are available from ‘Documentation’ tab of the product page.

6.3

Design assist tools are available from ‘Tools’ tab of the product page.
The Circuit constant calculation sheet is useful for Febiding the application circuit constants.

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Notice

Notes1) 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.
6) The Products specified in this document are not designed to be radiation tolerant.
7) For use of our Products in applications requiring a high degree of reliability (as exemplifiedbelow), please contact and consult with a ROHM representative : transportation equipment (i.e.
cars, ships, trains), primary communication equipment, traffic lights, fire/crime prevention, safety
equipment, medical systems, servers, solar cells, and power transmission systems.
8) Do not use our Products in applications requiring extremely high reliability, such as aerospaceequipment, nuclear power control systems, and submarine repeaters.
9) ROHM shall have no responsibility for any damages or injury arising from non-compliance withthe recommended usage conditions and specifications contained herein.
10) ROHM has used reasonable care to ensure the accuracy of the information contained in thisdocument. However, ROHM does not warrants that such information is error-free, and ROHM
shall have no responsibility for any damages arising from any inaccuracy or misprint of suchinformation.
11) Please use the Products in accordance with any applicable environmental laws and regulations,such as the RoHS Directive. For more details, including RoHS compatibility, please contact a
ROHM sales office. ROHM shall have no responsibility for any damages or losses resulting
non-compliance with any applicable laws or regulations.
12) When providing our Products and technologies contained in this document to other countries,
you must abide by the procedures and provisions stipulated in all applicable export laws andregulations, including without limitation the US Export Administration Regulations and the Foreign
Exchange and Foreign Trade Act.
13) This document, in part or in whole, may not be reprinted or reproduced without prior consent ofROHM.

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