Single

box-power

circuit schematic for iso-container in-box DC-DC convertor support board.

i6A4W

The DC-DC convertor is an adjustable, 250W, 9 to 53V Input Non-Isolated Step Down DC-DC Converter [https://www.farnell.com/datasheets/3312958.pdf], which we purchased from Farnell.

The part does not exist in the standard KiCAD library.

There is a "free" component design available here but the license prevents redistribution, so I created the part from scratch.

Pin Sizes

Small

• pins DIA 1.02 [0.040]
• standoffs DIA 1.78 [0.070]

Large

• pins DIA 1.57 [0.062]
• standoffs DIA 2.59 [0.102]

Hole sizes

Samtec recommended hole sizes are as follows:

Lead size 1.14 [0.045] Dia hole 1.30 [0.051] Dia i.e 1.14x, or +0.16mm Lead size 1.32 [0.052] Dia hole 1.47 [0.058] Dia i.e 1.12x, or +0.15mm

Most of the other entries show 0.15mm increase from pin to hole size, so not a percentage

Practical Electronics recommends adding 6mils to round leads, i.e. 0.15mm.

JLBPCB hole sizes are 0.2mm -6.3mm The tolerance is +0.13mm/-0.08mm

Minimum annular ring 2oz copper is 0.2mm, 0.3mm for PTH

It seems that the hole is enlarged in production ... so there is no need to allow for the PTH thickness?

so ... pin size 1.02 1.57 add 0.08mm tolerance 1.10 1.65 add 0.15mm clearance 1.17 1.72 next largest round 0.1mm 1.2 1.8

Also see IPC-7251, IPC-2222 and IPC-2221 for pad sizes as described here

The general density is level A, easiest to fabricate. Pad Diameter = Minimum Hole Size + 0.1mm + 0.60mm (for Level A of IPC-2221) So... 1.2mm +0.1mm +0.6mm = 1.9mm diameter for the smaller pins 1.8 + 0.1mm +0.6mm = 2.5mm for the larger pins.

Y-offset of the pins 32, 33 is calculated as

reference up to top of board 3.8mm top of board to bottom of board 22.9mm bottom of board up to holes 2.5mm -- calculations pin8 centreline down to bottom of board = 22.9-3.8mm = 19.1mm pin8 centreline down to pin32 = 19.1mm - 2.5mm = 16.6mm

Unconnected inputs

No optional features ordered ( I6A-4W0-20A-033V/001-R,)

ON/OFF

We ordered the 01 variant so negative logic on/off

Connect ON/OFF pin to ground (see p19, remote on/off)

Consider derisking with a solder bridge option here?

Power good

Leave open (see p20, top of right column)

Synchronization

Not a specified option, so leave open 32 SYNC, 33 MS

Sequencing

Not an option - leave open.

RUP

See p20 in datasheet, for 20A device.

5V 8k4 (should be 8k6, but this was the closest we could get, and will produce slightly higher voltage as typical of USB bus)

12V 1k82

Safety

Fuse 30A

See p22 - select 30A fuse max, can choose smaller if you want.

Footprints

Ordered from CPC Farnell

RC55Y-8K45BI

RC55Y-8K45BI Through Hole Resistor, 8.45 kohm, RC Series, 250 mW, ± 0.1%, Axial Leaded, 350 V

8k45 trim resistor

L 7.2mm D 2.5mm lead 0.6 nom PCB mounting centres 10.2mmm Footprint: Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal

YR1B1K82CC

YR1B1K82CC Through Hole Resistor, 1.82 kohm, R Series, 250 mW, ± 0.1%, Axial Leaded, 500 V

length 6.3mm +/- 0.3 diameter 2.3 +/- 0.2 lead diamter 0.6mm nom

Can use same footprint as the other trim resistor

100uF

50YXF100MEFC8X11.5

8mm by 11.5mm

50V

8mm diameter 3.5 mm lead spacing 0.6mm lead diameter

Capacitor_THT:CP_Radial_D8.0mm_P3.50mm

21uF

50ML22MEFC8X5

8x5 variant (not 6.3x7)

diameter 8mm Leg spacing 2.5mm leg diameter 0.45mm

Capacitor_THT:CP_Radial_D8.0mm_P2.50mm

0.1uF

MCMHR50V104M4X7 Electrolytic Capacitor, 0.1 µF, 50 V, MCMHR Series, ± 20%, Radial Leaded, 1000 hours @ 105°C

4mm OD by 7mm length Leg spacing 1.5mm +/- 0.5mm leads 0.45mm OD

Capacitor_THT:CP_Radial_D4.0mm_P1.50mm

Fuse holder

Solder pins 0.5mm x 1.2mm

two holes 1.5mm diameter, spaced by 22.6mm

nearest existing footprint: Fuse:Fuseholder_Cylinder-5x20mm_Schurter_0031_8201_Horizontal_Open modified by enlarging holes to 1.5mm diameter (ends), 3.2mm middle: box_power:Fuseholder_Cylinder-5x20mm_646_series_22.6_1.5

Ø 3mm screw hole may be used optionally - this is the central hole

DC Plug

DC10B, DC Power Connector, Jack, 5 A, 2.5 mm

3.5mm by 1mm tines 5mm spacing between 1,3 and 2 13.55-7.4 = 6.15mm spacing between 1 and 3 1 is centre 3 is ground 2 is plug detect

CENTRE POSITIVE SO CAN BE UNPLUGGED LIVE

USB A receptable

Multicomp

CONNFLY_DS1095_WNR0 is correct compared to the datasheet - renamed and put in box power for certainty later.

Fan

12V Fan

40mm by 10.5mm with 3.4mm diameter holes on 32mm centres so use 2.5mm cable ties in 3.5 by 2mm holes spaced 2mm from the fan

the leads are 26AWG, or 0.4038mm.

So the hole should be ... +0.23mm or 0.66mm diameter total, i.e 0.7mm drill the pad should be 0.7mm bigger, or 1.4mm pad

Track sizing

5mm track ok for 10A current and 20degC rise.

If we have 20A flowing, then temp rise will be closer to 85 degrees - however, this should not happen for long ....

Parts from order

Part no. Description Quantity Price 1 PW04096 24V 25A 600W Constant Voltage LED Driver, IP67 Rated - LED-DR-24V-600W-A 6 £172.32 2 2664687 I6A-4W0-20A-033V/001-R, Non Isolated POL DC/DC Converter, ITE, 250 W, 3.3 V, 15 V, 20 A, Adjustable 30 £22.47 3 2518207 CP30222SM In-Line Adapter, RJ45, RJ45, Adaptor, In-Line, FT Series, Jack, 8 Ways 30 £6.18 4 892373 NAC3MPA-1 High Power Connector, PowerCON Series, Receptacle, 250 VAC, 20 A, Panel Mount, Quick Connect 30 £2.80 5 892350 NAC3FCA High Power Connector, 3Pin, Blue, powerCON Series, Receptacle, 250 VAC, 20 A, Cable Mount, Screw 30 £4.94 6 2425457 Multicore Cable, Flexible Mains, 20, Per Metre, Unscreened, 2 Core, 2.5 mm² (one continuous length of 50m) 50 £1.96 7 224960 DC10B, DC Power Connector, Jack, 5 A, 2.5 mm, Through Hole Mount, Solder, pack of 10 10 £4.28 8 224935 DCPP2, DC Power Connector, Plug, 5 A, 9.5 mm, Cable Mount, Solder, pack of 10 10 £5.80 9 1871011 MCMHR50V104M4X7 Electrolytic Capacitor, 0.1 µF, 50 V, MCMHR Series, ± 20%, Radial Leaded, 1000 hours @ 105°C 50 £0.04 10 8126968 50ML22MEFC8X5 Electrolytic Capacitor, Miniature, 22 µF, 50 V, ML Series, ± 20%, Radial Leaded, 3000 hours @ 105°C 50 £0.15 11 1144634 50YXF100MEFC8X11.5 Electrolytic Capacitor, Miniature, 100 µF, 50 V, YXF Series, ± 20%, Radial Leaded 50 £0.17 12 2816685 MC002106 DC Axial Fan, 12 V, Square, 40 mm, 10.5 mm, Sleeve Bearing, 5.2 CFM 30 £1.76 13 1083279 YR1B1K82CC Through Hole Resistor, 1.82 kohm, R Series, 250 mW, ± 0.1%, Axial Leaded, 500 V 50 £0.37 14 9503005 RC55Y-8K45BI Through Hole Resistor, 8.45 kohm, RC Series, 250 mW, ± 0.1%, Axial Leaded, 350 V 10 £1.24 Total: £2911.34

Track sizing thoughts....

if not using both sides of the board, better to go to 7mm AND 2oz copper, and keep temp rise down to 15deg.

Reverse polarity protection

There are several options we can consider - just using a MOSFET, adding a ORING controller such LM5050 (not in stock at JLCPCB, no DIP package?), or IDP90PO3P4L-04 (check code!) as used in the infineon DC motor shield. The TI part LM5050 seems to use a number of external components.

Designing a simple MOSFET based system is described by TI application note.

Main consideration is getting low R_DS_ON, with power dissipation being R_DS_ON * I_LOAD.

world's lowest RDS_on at 30V, intended for reverse voltage protection: https://www.infineon.com/dgdl/Infineon-I80P03P4L_04-DS-v01_01-en.pdf?fileId=db3a30431ddc9372011e07e95eb827d7

-80A continuous drain current VGS+5/-16V ?? Ptot 137W VDSmax for breakdown 30V 7mOhm x 10A = 7e-3x100 = 7x0.1 = 0.7W, compared to 240W total power, so <1%

but not recommended for new designs

Maybe this:- https://uk.farnell.com/vishay/sqp100p06-9m3l-ge3/mosfet-p-ch-60v-100a-175deg-c/dp/3470727

suggested safety margin of nearly x2 on VDS, and use of zener for protection of VDS https://components101.com/articles/design-guide-pmos-mosfet-for-reverse-voltage-polarity-protection

lead size 1.01mm max, wide side of legs (wide side of body), 0.36 - 0.61mm narrow side spacing iunside to outside leg 2.4-2.67mm, outside legs 4.88 - 5.28mm (so 5mm nominal)

Pin order left to right from front: GDS

package: TO 220AB

Connections:

VBAT goes to DRAIN GATE Goes to resistor/zener junction SOURCE goes to top of zener, and top of load. bottom of resistor goes to ground.

See Infineon Application note for tradeoffs between diode, N-channel with charge pump and P-channel

Package_TO_SOT_THT:TO-220-3_Vertical

Zener diode

Since VGS max is +/-20V, choose 18V Zener. 5% is 0.9V.

https://uk.farnell.com/nexperia/bzx79-c18-133/diode-zener-0-5w-18v-do-35/dp/1097219?st=zener%20diode

Body length 4.25mm, diameter 1.85mm, lead size 0.56mm max DO-35

Diode_THT:D_DO-35_SOD27_P7.62mm_Horizontal

bias resistor

Zener power dissipation is 500mW, so at 18V would be 27mA current max. Call it 20mA

Expect a reverse voltage of 24V, so 6V to drop across resistor. MAx current 20mA V=IR so R = V/I = 6/20mA = 300R

this should be consistent with a fast enough switch for reverse polarity protection.

MFR4-300RFI 0.5W 6.2mm body length max, diamter 2.5mm professional version

Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal

HEATSINK

possibly this one....

MC33278