BD9328EFJ, BD9329AEFJ Eval Brd Application Note Datasheet by Rohm Semiconductor

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ROHm Application Note ssmcnubuflnx , r, ROHM SEMICONDUCYOR ©2012 ' Q
1
ROHM Switching Regulator Solutions
Evaluation Board:
Step-down Switching Regulator
With Built-in Power MOSFET
BD9328EFJ / BD9329AEFJ (12V | 2A / 3A Output)
Introduction
This application note will provide the steps necessary to operate and evaluate ROHM’s step-down switching regulator using the
BD9328EFJ/BD9329AEFJ evaluation boards. Component selection, board layout recommendations, operation procedures and application
data is provided.
Description
This evaluation board has been developed for ROHM’s step-down switching regulator customers evaluating BD9328EFJ and/or
BD9329AEFJ. While accepting a wide power supply of 4.2-18V, a step down output of 3.3V or any external resistor defined voltage can be
produced. The ICs have two integrated low resistance N-channel MOSFETs and a fixed synchronization frequency of 380 kHz. A Soft Start
circuit prevents in-rush current during startup along with UVLO (low voltage error prevention circuit) and TSD (thermal shutdown detection)
protection circuits. An EN pin allows for simple ON/OFF control of the IC to reduce standby current consumption.
Applications
Distributed Power Systems
Pre-regulator for linear regulators
Evaluation Board Operating Limits and Absolute Maximum Ratings
Parameter Symbol
Limit Unit Conditions
MIN TYP MAX
Supply Voltage
BD9328EFJ VCC 4.2 12 18 V
BD9329AEFJ VCC 4.2 12 18 V
Output Voltage / Current
BD9328EFJ VOUT - 3.3V - V
BD9329AEFJ VOUT - 3.3V - V
BD9328EFJ IOUT - - 2 A
BD9329AEFJ IOUT - - 3 A
Evaluation Board
Below is the evaluation board with the BD9328EFJ. BD9329AEFJ eval board uses the same components and board layout
No.0000000014
Vout Vin
High
E
N
Low
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Evaluation Board Schematic
Below is the evaluation board schematic for BD9328EFJ. BD9329AEFJ eval board uses the same schematic
Evaluation Board I/O
Below is the reference application circuit that shows the inputs (Vin and EN) and the output (SW and FB)
Evaluation Board Operation Procedures
Below is the procedure to operate the evaluation board
1. Connect GND to a GND pin on the evaluation board
2. Connect Vin to the +12V_Vin pin. This will provide Vin to the Vin pin of the IC
i. Note: EN pin is pulled high as when SW1 is high (white arrow)
3. Now output power can be measured from the +3.3V_Vout pin on the evaluation board with a load attached
. . gm _ VWrmx:Ma-u W Van A:15.2 mV n... mm Vom .M van mumvlm ansnmvmiv low ‘ fu ‘ I hatllelDiv ‘ lam |n|ml.0AIDiv ‘ ‘ W“ . ‘ ‘ » W m?“ m: I, .1 - "W . Wm mar". :54", .3 Jam Response ompm Ripple Vnhage (VII:IZVVun:31VL:IWH mflMF may M) WIZVVMFSZVL:IWHOII:2fluFlun:IMI Vow: Ion mVlDiv n: a w a , m :n-mu m law ‘7 ‘7 mummy I JDAIDEV mm Jam“ nnmn . \ .5. mo L. MN mm. mm 07* . ‘ ‘ N H mm. y”, m. . . N. ‘ mm. 7mm, Translem Rspmse ‘ cum-n Ripple Vuflage (VIN: Izv Vow; 3.3V L=1fl|lN com =2mF In: a.“ W Euziavloiv I “ —> : I VourLflVlDw um... mm H - rwlpwl 4 StanUpmvdmm (VIN: INVM: 3 CWL: "IAN Cu: OJIFY Mmmw«=nv|;umm=mlmzm) as so as an 7 ‘515 E gm as an as an n smumuanzummm um STEP Down Efficiency (VIN: Izv Vow: 3.3V L=|0qu
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Reference Graphs Application Data for BD9328EFJ
Below graphs shows load characteristics, transient responses and efficiency of the BD9328/9 eval board.
VolnMAx: “8|le Vallmmleiv Tmnsiem Response (VIN: IZV Vow: 33V L= IUIH com=nuF W024 M) Vuln-MAX' olzolnv Vow—MIN: “HIV . l I Vow: 100 "IV/Div Inn IMJBAIDiv Tmlem Response (VIN: IIVVom: 33V L: IHIH (30“:ZZIIF |o\l:02-3W ikmvu H u A' 251 mV Vow. Vour. ln.o IllVlD'gv v laur, IDA/Div Ioln “W mm, A w , mTw 3mm Ripple Vollage le I2VVM:33VL= lnmm=22u=loul=l 11A) mm H u A12“! mV Vom’ an- Ilul mVI Div lmn:1,|)AlDw AFT-2»: A in: 1 mm m mourn "Ir-mu Output Rlpple Voltage (VN:IZVVDIII=13VL:IWHC¢I:DIIFIO‘I: 8 M) mime 95 EN EN:10VIDIV an m _ m i; 75 Vow Vour:lUV/Div 5 g m N 5 m 56 an low . l. ,. lwmnum a m um um am m m if A 0.. I . w m mm mm m .‘zm. um STEP Down Efficiency Stan Up wave'oml MN=12VVM= 3 3v L= low Cu: 0 NF) MN: 12v Vouv: 3 3v mow)
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Reference Graphs Application Data for BD9329AEFJ
Below graphs shows the load characteristics, transient responses and efficiency of the BD9329AEFJ eval board.
Two hIgh pulslng eunenl llowlng loops exls1 In ms nu regulamr system The hrsl loop, when PET Is ON, stuns lmIn Ihe Inpul capacnars, no lhe VIN hermInaI, no lhe sw lerrIIInaI, lo the Inducmr, Io lhe oulpul capacnars, and then relums lo the Input capacIIpr mrough GND The second loop, when PET Is OFF, stuns from The low PET, m The Inducmr, In me oulpul capacnor, and Ihen relums no me low PET mrough 6ND To reduce The anse and Imprnve Ihe emcIeney, please InInIInIze mese Mo loop area EspecIally Inpul mpacmor, culpul capacnor and low PET should he connected Io 6ND plaIn, PCB Layout may affect me Ihennal perlannance, noIse and emcIeney greatly, So please take em care when deslgnlng PCB Layoul pallems, le L T LU W 9 an s Pg 25 CurrenI loop In Buck regulamr syslern - The rhennal Pad on The back sIde of IC has lhe great lherrna oondualon m Ihe chIp, 30 using lhe GND plaIn as broad and Wlde as posslhle can help Ihennal dIsstahnn And a lm of Ihennal Ina fur helpIng me spread of heal Io me dIlTerenI layer Is also efiecnve - The Inpur capacnars should be cannected as close as posslhle no me VIN IennInal, - Keep sensIIIIIe slgnal Imces such as Iraoe oonneaed FE and COMP army from sw pIn - The Induular and Ihe oulpul mpacmols should he planed close up sw pm as much as possIhle, ClN EST VIN s COMP Pl umum GND '- Co T a P VouT Al F l l Pg 25 The example of PCB laypul pahem
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Evaluation Board Layout Guidelines
Below are the guidelines that have been followed and recommended for BD9328EFJ and BD9329AEFJ designs
Note:
For applications operating at or near maximum voltage conditions (20V max.), additional precautions regarding heat
dissipation need to be considered during board layout. The provided evaluation board is a 2-layer board meant for evaluation
purposes only. At maximum conditions, the IC’s internal thermal shutdown detection circuit will be potentially initiated and the
output disabled until the junction temperature falls. For final designs operating near these conditions, we recommend using
one of the below PCB options for better heat dissipation of the IC.
1) Use of a 4-layer PCB with internal GND planes connected to the IC GND pins
2) Use of a 2-layer PCB with a heat sink attached to the IC package
3) Use of a 2-layer PCB with a copper plane (>1oz) attached to the IC
.Selecting Appiutlon Components (I) Output LC liner constant selection (Buck convenen The oulpnl LC finer Is requrred to supply oonslanl current to the output lead. A larger value lmhctanoe at this liter Insults In I55 inductor npple cun'enKAl) and less output llpple millage, Hawsvef, "E Ialger value illillchrs Iend 10 have less last load Hallsiem-deswlse, a larger physrcal size, a lower salulanm cunent and hrgher senes lesismnce, A smaller value rnduclanre has almost opposite draraclenslios above. So elloosrng lhe lnduclor npple curremlAlr) between 20 lo 40% at me averaged Inducmr curem (equrvalent lo the output load mrrenl) Is a good compromise, I IOUT'MX + AIL [2 L should not reach VI» Ihe rand value level _‘ - ------------------------------------------- rm Vow E lnduaor averaged current L I Cour ( I -—> W Fngfl Fig 19 Se‘llng Al 30% xAvelzged Inductor mnenl (2A) : 0,6 [A] 1 L = Von x (Vn . Vow) x = 10;: [H] Vrn x ch x AIL Where We 12v, Vow: 3,3V, Fosc: 330 erL ; Fosn: Is a swrluung lrequency Alsu me 'llductaf sholld have me [fuller saturation current man lourwlx 9 All] 2, The outpul capacflor Cour alleas the output npplevoltage Choose the large capaenor to achreve lhe small nppbevohage enough lo meet the applroatlon requirement Output ripple voltage AVRPL is calmlated by the following equation 7 1 AVRPLr Ale(Rmo Momma“ ) [V] Where Rest: Is a parasm'c senes resistance in output apacllor. Sellrng Cot": 20uF, Risk :1DmQ AVRPL:0.6X(10m+ 1/(8x20ux38lk)):15,8mv
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Item Qty 1 2 3 4 m 904$ 11 1 1 1 (3) Design 01 Feedback Ress1ance mum“ Se’l file feedhank resislance as Shawn balm T1 DEV Vow V1117: RI % 9 .FB R2 #7922 Ref Descriptlo Manufacturer 07001 CAP CERZZUF16’V20% 1206 TDKCerporafion C_PC CAP OER 3300PF100V10%X7R0805 TDK Corporah'on C_VC1 CAP CER 10UF 25V 10% 121 0 TDK Corporation L1 INDUCTOR SH‘ELD PWR1OUH SMD TDK Corporation 2:: CAP CER 0.1 UF 25V10%X7R 0505 TDK Corporation RBS RES 2 OHM 1IBW 5% 0905 SMD ROHM Semiconducwr RDW RES10KOHM 1/BW5%05055MD ROHM Semiconducmv RPC RES 7.5K OHM 1/8W 5% 0805 SMD ROHM Semiconductor RUP RE527KOHM 1/8W5%0805$MD ROHM Semiconduckzr ICREG BUCKSYNC ADJZA . U1 BHTSOP ROHM Semlcnnducwr IC REG BUCK SYNC ADJ 3A U1 BHTSOP ROHM Semvcunductcr Pa rt N u m be r C321 GXSS1CZSM 6201 2X7R2A332K 03225J B1 E106K c3225v5v1 H1 062 02012X7R1E104K/1 25 MCR10EZHJ220 MCR1OERTJ103 MCR10EZPJ752 MCR1 0EZHJ273 BDQSZBEJ—EZ BD9829AEFJ-E2 Dlg Ikey P/ N 445-8044r6—ND M5—M31-2-ND 4457354667ND “seams-ND 445-1351-2-ND RHMZZATR-ND RHMWOKCLTR-ND RHMIEKARTR-ND RHM27KATR-ND BWSZBEFJ-EZTR—ND BD9329AEFJVEZTRV ND
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Evaluation Board BOM
Below is a table with the build of materials. Part numbers and supplier references are provided.
Note: In this example, the nominal resistance values of R1 and R2 were selected to set a
3.3 V output.
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