minikv bill of materials, rev 1

Components marked "crit" are critical and should be populated with exactly the recommended manufacturer part number in the table. Reasons for these critical parts are explained below so they may be substituted if absolutely necessary, but do this with care.

Components with no part number are common parts expected to be provided by the builder according to the description.

Parts with reference numbers greater than 10 are on the secondary winding board.

Part Description Crit Manufacturer Manufacturer's part number
C1 Capacitor, MLCC, 47nF, 100V, C0G, 1206 KEMET C1206C473J1GEC7210
C2-3 Capacitor, MLCC, 1µF, 25V, X5R, 0805
C4 Capacitor, MLCC, 330pF, 25V, C0G, 0603
C5 Do not populate
C11-14 Capacitor, MLCC, 6.8nF, 2kV, X7R, 1210 KEMET C1210C682MGRAC7800
C15 Capacitor, MLCC, 27nF, 2kV, X7R, 2220 KYOCERA AVX 2220GC273KAZ1A
D11-14 Diode, 1kV, 1A, trr ≤ 75ns, SOD-128 Taiwan Semi HS1MFS
J1 Header, shrouded, 1x8, 2.5mm JST B8B-XH-AM(LF)(SN)
L1 Inductor, 220µH, 600mA, 6x6mm Yes Bourns SRN6045-221M
L11 Inductor, 1mH, 15mA, 1007 Taiyo Yuden LB2518T102K
Q1, Q2 Transistor, NPN, 100V, 1A, low Vcesat, SOT-23 Yes Nexperia PBSS8110T,215
Q3 Transistor, NMOS, 40V, 20A, TO-252 Yes Alpha & Omega AOD454A
Q4* Transistor, NPN, 40V, 200mA, SOT-23 (for mod) any MMBT3904
R1 Resistor, 10M, 1%, high voltage, 2010 Yes Bourns CHV2010-FX-1005ELF
R2 Resistor, 18k, 1%, 0603
R3 Resistor, 7.5k, 1%, 0603
R4 Resistor, 100k, 5%, 0603
R5 Resistor, 1.5M, 5%, 0603
R6 Resistor, 3.3k, 5%, 0603
R7, R11 Resistor, 430, 5%, 0.4W, 0805 Rohm Semi ESR10EZPJ431
R8 Resistor, 1 ohm, 5%, 2/3 W, 1210 Rohm Semi ESR25JZPF1R00
R8* Resistor, 0.75 ohm, 1%, 1 W, 1210 (for mod) Vishay Dale RCWE1210R750FKEA
RV1 Potentiometer, 200k Bourns TC33X-2-204E
U1 1.24V shunt reference, 16V max, SOT-23-5 Yes onsemi TLV431BSNT1G
n/a Planar E-core, 22x16mm Yes Ferroxcube E22/6/16/R-3F36
n/a Planar E-core plate, 22x16mm Yes Ferroxcube PLT22/16/2.5/S-3F36
n/a Planar E-core transformer clamp Yes Ferroxcube CLM-E22/PLT22

L1: "Critical" due to proprietary footprint. If you can find one that fits, go for it. Irms and Isat should both be 600mA or higher.

Q1, Q2: These are low-Vcesat transistors meant for use in SMPS circuits. Using "normal" transistors in place of these may cause overheating and failure. If needed, Zetex and Nexperia have many alternatives.

Q3: Because this MOSFET is used in a linear mode, it must have some specific properties. First, the datasheet must have a "forward-biased safe operating area" (FBSOA) plot. It will have several curves for different pulse durations. The transistor used here must have a "DC" curve in this plot, and that curve must include 3V, 1A. MOSFETs not meeting this may suffer from thermal runaway and fail. Second, the minimum VGS(th) (threshold voltage) must be no less than 1.5V at 250µA. This ensures that the TLV431 is capable of fully shutting it off. Third, RDS(on) must be less than 0.75 ohms. Most MOSFETs do meet this one, but it rules out some high-voltage parts that would otherwise be well suited.

R1: This resistor must permit continuous operation at up to 2000V and have a power rating of at least 250mW. Don't just filter for "high voltage" at Digi-Key, check for "maximum working voltage" in the datasheet.

U1: Not all TLV431s are equivalent. In this circuit, a maximum operating voltage ("cathode" voltage) of 16V or higher is required. Also, frequency response can slightly vary between manufacturers, so compensation components R5, C4, and C5 may need to be changed to support a different U1.

Transformer core components: These are completely critical, the board is designed around them. If you can find a piece of similar ferrite material that will fit in the same place, it might work, but don't count on it. If this piece is obsoleted we'll have to make a new minikv.

Last modified: Sun Oct 23 18:25:58 MDT 2022. Converted from projects/minikv/
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