And now for something completely different

And now for something completely different

First results from the DC-DC StaveletPeter & Ashley

with Giulio & John

2

DC-DC Stavelet First Module

Unstuck?

Power ONPower ON

Power OFF

SE4445 is used to attach modules tostavelets. At room temperature, this takes a long time to cure. When the module was first powered, it bowed as shown. It’s notquite as bad now, but it does still bow.• Do we need to remove and re-attach this module or is it OK to leave it?• If we use SE4445 for further modules, do we need to allow a longer cure before application of power?

H0H1

3

4

Chip & Strip Numbers

32 33 34 35 36 37 38 39 40 41

64 65 66 67 68 69 70 71 72 73

BCC

Edge

DC-D

C Ed

ge

Channel 0 Channel 1279

Strictly, the hardware channel numbering is contiguous only for the upper column. Chip 64 for example has channel 127 at the sensor

edge – but in all plots which follow this has been corrected in software to match the above labels.

5

ShieldConnections

(IN USE)

ShieldConnection

(NOT IN USE)

BackplaneConnection

(H1 only)

Shield Referencing

Option toLink LVDS& SensorShields

6

H0 Original ShieldH1 Original Shield

Both hybrids at Once

H0 Original ShieldH1 Unpowered

H0 UnpoweredH1 Original Shield

10/06/2011, 10V 3.0A limit, H0 DC referenced to shield, H1 AC referenced to shield

H0 Outer Column

H0 Inner Column

H1 Inner Column

H1 Outer Column

ENC MeasurementsCh 0 -> by BCC

Ch 1279 -> by DC-DC

710/06/2011, 10V 3.5A limit, H0 DC referenced to shield, H1 AC referenced to shield

H0 Wrapped ShieldH1 Wrapped Shield


H0 Wrapped ShieldH1 Unpowered

H0 UnpoweredH1 Wrapped Shield

ENC MeasurementsCh 0 -> by BCC

Ch 1279 -> by DC-DC

8

Cursory investigation of B fieldalong axis through converter centres

0 5 10cm

Converter PCB now closer to the hybrid edge than for the

single module DC-DC tests (~2mm from

~7mm) and it’s also now in the same

plane. Therefore the scope for pickup is

increased.

9

HMS3000 Typical Screenshot

Shields wrapped in Cu tape, both converters running, 3cm point

10

Shields Removedboth converters running

0 2 4 6 8 10 12 14 16

-90

-80

-70

-60

-50

-40

-30

1.96 MHz3.91 MHz5.87 MHz7.85 MHz9.80 MHz

NoiseFloor

cm

dBmNot Calibrated: relative measurement only

11

Shields Removed H0 converter running, H1 powered down

0 2 4 6 8 10 12 14 16

-90

-80

-70

-60

-50

-40

-30


NoiseFloor

cm


12

Shields Removed H0 powered down, H1 converter running

0 2 4 6 8 10 12 14 16

-90

-80

-70

-60

-50

-40

-30


NoiseFloor

cm


13

Shields Wrapped in Copper Tapeboth converters running

0 2 4 6 8 10 12 14 16

-90

-80

-70

-60

-50

-40

-30


NoiseFloor

cm


14

Shields Wrapped in Copper TapeH0 converter running, H1 powered down

0 2 4 6 8 10 12 14 16

-90

-80

-70

-60

-50

-40

-30


NoiseFloor

cm


15

Shields Wrapped in Copper TapeH0 powered down, H1 converter running

0 2 4 6 8 10 12 14 16

-90

-80

-70

-60

-50

-40

-30


NoiseFloor

cm


16

Field leaks through gap between shield and converter PCB

Will a “skirt” help?fitted over existing

layer of copper tapeH0

H1

Also revised hybrid referencing to make both DC referenced

17

Effect of “Skirt” on B field

These measurements were made using the smallest magnetic field probeplaced immediately adjacent to the converter shield of hybrid H0 of the

single DC-DC module M5 (not stavelet module M13).

WITHOUT SKIRT WITH SKIRT

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One hybrid at a time

H0 Wrapped + SkirtH1 Wrapped Shield


H0 Wrapped + SkirtH1 Wrapped Shield


21/06/2011, 10V 5.0A limit, Both hybrids DC referenced

19





H0 Original ShieldH1 Wrapped Shield


H0 Original H1 Wrapped Shield


21/06/2011, 10V 5.0A limit, Both hybrids DC referenced

20

TEST 1: 5.0AWrapped Shields








22/06/2011, 10V variable current limit, Both hybrids DC referenced

TEST 1: 21/06/11Sensor Shield DC

@ BCC edgeBoth hybrids at Once


@ BCC edgeEach hybrid separately


@ both edgesBoth hybrids at Once


@ both edges Each hybrid separately

Wrapped shields used throughout, TTi supply at 10V 5A limit

22

Double Trigger Noise @ 0.75fC

TTi TSX3510P @ 10V, wrapped shields, both hybrids at once (yes it really is this clean)

23

Double Trigger Noise @ 0.50fC

TTi TSX 3510P @ 10V, wrapped shields, both hybrids at once

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Summary• Increasing the TTi TSX3510P PSU current limit above 3.0A has no

effect upon the ENC noise– Avoid values below this

• supply will not trip but may current limit

• Referencing changes have had a greater effect than increasing the mass of the shields– Extra 2 bonds per hybrid at DC-DC edge helped reduce the noise

• Beyond that, all that’s present in the design is the option to connect the sensor shield pad to the LVDS shield.

• Next : further reduce inductance of the shield connection– How can we improvise Cu or Al foil connections between Al shield and

adjacent DC-DC power return line?• See over for first attempt....

25

Lowering the Inductance of the Shield Connection

1. Remove kapton tape from power bus2. Partially remove kapton cover from sensor shield3. Add a dozen bonds to connect them together=> Sensor Shield is connected directly to power GND


@ both edgesBoth hybrids at Once


@ both edges Each hybrid separately

NEW TEST 5: 29/06/2011Sensor Shield DC & to power return



& to power Return Each hybrid separately

Wrapped shields used throughout, TTi supply at 10V 5A limit

27

Future Plans

• Continue to lower the inductance of the shield connection

• What if this does not work?

????

Backup

29

Naked Converters!Converter 06: BC0000000476043A Converter 14: 7C0000000455D23A

Q) Does the precise physical orientation of each coil have any great significance?

30

M13 Single Module Result

(SP @ Liverpool)

M13 Stavelet Bestrunning both at once

Wrapped Shields

M13 Stavelet Bestrunning one at a time

Wrapped Shields

And now for something completely different

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