Powering for the 2S-ModuleRandom Thoughts

CEC MeetingAachen, 21st of March 2012

Katja Klein1. Physikalisches Institut B

RWTH Aachen University

3D-Model with realistic Buck Converter

Katja Klein 2Powering the 2S-Module

DC-DC buck converterComponents based on smallestversion of our pixel converters It fits on the “service hybrid“

Buck Converter AC_PIX_V8_E

Katja Klein 3Powering the 2S-Module

We (Aachen group) develop buck converters based on CERN ASIC for pixel upgrade

Our smallest board:V8 E: 2.6cm x 1.5cm; 1.5 -1.6g

ASIC: AMIS4 by CERNVout = 3.3V or 2.5Vfs = 1.5MHz2-layer PCBToroidal plastic core inductor L = 450nHPi-filters at in- and output

Why is a shield required? to shield the magnetic emissions as cooling contact for the coil to segregate “noisy“ parts from output filters

inV loadR

L1T

2ToutVont

ASIC

Buck Converter Remote Control

Katja Klein 4Powering the 2S-Module

Two features implemented in AMIS4:

• Disable / enable input

• Status bit (“power good“)

Need to be controlled from an independently powered unit, otherwise useless.

In phase-1 pixel detector, we plan to use the CCU as controller.

The Slow Control ASIC (SCA) of the GBT could be used for the outer tracker.

Since a “module controller“ is not foreseen, a “rod controller“ would be required.

Vin

VoutVout_Return

StatusDisable/enable

ASICCoil

Vin_Return

DC-DC buck converter

Material Budget

Katja Klein 5Novel Powering Schemes

• Contribution of buck converter, comp. to CMS modules (1 converter per module)

Standard DC-DC X0 [%] 1

DC-DC / module

Minimized DC-DCX0 [%] 1

DC-DC / module

Todays module 0.06 8.8% 0.04 5.9%

Pixelated trigger 0.16 16.1% 0.11 11.1%

Strip trigger 0.14 15.4% 0.09 9.9%

Stereo module 0.14 9.9% 0.09 6.3%

• Contribution of buck converter, compared to ATLAS stave (1 converter per hybrid)

Standard DC-DC X0 [%] 1

DC-DC / stave

Minimized DC-DC X0 [%] 1

DC-DC / module

Ultimate DC-DCX0 [%] 1

DC-DC / stave

Stave 0.1168 21.8% 0.056 10.4% 0.032 6.0%

Powering circuitry itself might contribute with 5-10% to module material budget

1 normalized to respective module or stave area

“Minimized“: Aluminium coil, no connector, less filter caps

The Conversion Ratio

Katja Klein 6Powering the 2S-Module

Conversion ratio:out

in

V

Vr

• Semi-conductor technology limits input voltage to Vin < 10V

• We will need Vout = 1.2V

Maximal achievable conversion ratio is r = 10V / 1.2V = 6.7

• Cables channels can support 15kA

• Total power of detector might be 57kW (Stefano Mersi) 48kA at 1.2V Need r = 4.3 for 75% overall power efficiency Want r as high as possible to decrease the cable material budget

• All our studies (efficiency, noise, …) are currently performed for Vout = 2.5V and 3.3V

• Previous measurements with AMIS2 showed efficiency of only 50-60% for Vout = 1.2V

• AMIS4 does not provide a (straight-forward) possibility to switch Vout to 1.2V

Efficiency vs. Conversion Ratio

Katja Klein 7Powering the 2S-Module

AMIS2 with Vout = 3.3V AMIS2 with Vout = 1.2V

0tan28a566028 0tan1a566010tan4a56604

0tan9a56609

0tan14a566014

0tan19a566019

0tan24a566024

0tan29a566029

Output current [A]

Eff

icie

nc

y [

%]

Vin = 6V r = 1.8Vin = 8V r = 2.4Vin = 10V r = 3.0

AMIS4 with Vout = 3.3V

Power Requirements

Katja Klein 8Powering the 2S-Module

• CBC chips: 2 x 8 x 60mA = 1016mA @ 1.2V• Data concentrator: 2 x 170mA = 340mA @ 1.2V ---------------------------------------------------------------------- 1.36 A @ 1.2V

• Low power GBT: official number is 500mW But – at what voltages? Try to understand from Sandro Marchioro

GBT would require 420mA @ 1.2V and 400mA @ 2.5V

Standard GBT best guess:GBTX:     1.4W at 1.5VGBSCA:   of the order of 0.3W at 1.5VGBTIA:    0.25W at 2.5 – 3.0VGBLD:     0.75W at 2.5 – 3.0V } this will not change !?

} 500mW at 1.2V (if 65nm)

Total current requirement of 1.8A at 1.2V fits to buck converter current capability of 3A

Note: bias current has to be provided conventionally

How to provide 2.5V (and 1.2V)

Katja Klein 9Powering the 2S-Module

Need to provide of the order of 400mA at 2.5V

Several options:

1. Provide 1.2V from buck converter and provide 2.5V conventionally

2. Provide 1.2V from buck converter and use “1:2 step-up“ switched capacitor converter to derive 2.5V from 1.2V

- Only the device from ATLAS is capable of providing 400mA

- 1.2V x 2 2.5V

3. Provide 2.5V from buck converter and use “2:1 step-down“ switched capacitor converter to derive 1.2V from 2.5V

- Switched cap. converter would be part of readout chip (+ data concentrator)

- Such a device has been developed by CERN

- First tests with CBC are promising

- Would allow to operate buck converter with relatively low conversion ratio higher efficiency (e.g. 0.8 x 0.9 = 0.72)

Novel Powering Schemes 10

Switched Capacitor DC-DC Converter

Katja Klein

• Two chips have been developed:- CERN (step-up and step-down, Iout = 60mA);

used by CMS in CMS Binary Chip- From LBNL (step-down, Iout = 500mA);

used by ATLAS in FE-I4

• Both with f = 1MHz

• Both „divide-by-two“ 1 external capacitor (1µF 0402 or 0603)

• Both chips do work - Efficiency lower than in simulation but still ~ 90%- Ripple large

CERN converter

Phase-1: charge Phase-2: discharge

Novel Powering Schemes 11

Switched Capacitor DC-DC Converter

Katja Klein

• Switched capacitor converter by CERN is part of 130nm CMS Binary Chip

• Used to convert 2.5V into 1.25V

• Could be combined with buck converter large r

• Works well, with efficiency of ~90%

• Spurious charge injected by transients increase of noise, but only for high input capacitance (will have 2.7pF)

• Same chip will be included in next, bump-bonded version of CBC (better coupling between grounds?)

1.78pF 5.79pF

Open Questions

Katja Klein 12Powering the 2S-Module

Module related• Where to place DC-DC converter?

Stave versus module

• How to bring power to the module? Define connectors, cables etc.

• How to bring power from converter to hybrids? One U-shaped hybrid vs. separate service hybrid

• Implementation of control communication

• Cooling of the DC-DC converter

• Noise performance – system tests with CBC and module prototypes

• Biasing

DC-DC converter related• How to achieve an efficiency of ~ 80% for a large conversion ratio?

• Find best combination of buck converter and switched capacitor converter

• Reduce material of buck converter