monsonpeer review – 5 december 2014 spp/fields lnps peer review steven monson university of...

Monson 1Peer Review – 5 December 2014

SPP/FIELDS LNPSPEER REVIEW

Steven Monson

University of Minnesota

[email protected]


3D View of Main Electronics Package


SPP FIELDS Instrument Block Diagram


LNPS Requirements

• Operate from 22 to 35 VDC

• Operate over the range of -25 to +60 degrees C base plate temperature– (derating to 75 C worst case board temperature)

• Must sync at 150 kHz but operate nominally without sync

• Provide DC voltage supplies– LNPS1 1.8V, 3.3V, 4V, 5V, +/- 6V, +/- 12V, +/- 100V– LNPS2 1.5V, 3.3V, 5V, +/- 6V, +/- 12V, +/- 100V– +/-100V supply to be delayed by 100ms from 5V supply (AEB

requirement)

• Total secondary power about 9.3w for LNPS1 and 5.7w for LNPS2

• Monitor and multiplex 10 voltages, LNPS temp and one SCM temp

• Provide sense circuit and control for SCM heater (LNPS1)

• Provide pass through of heater power for MAG


LNPS1 Customers

DCB RFS DFB AEB1 SCM MAGo(mA) (mA) (mA) (mA) (mA) (mA)

• 1.8V 250 (500) 364 (728)• 3.3V 300 (450) 125 (189) 1• 4V 170 160• 5V 120• +6V 44 50 11• -6V 44 26 11• +12V 8 11 13 52• -12V 5 11 12 28• +100V .5• -100V .5

Total 13 watts primary (16 hot)


LNPS2 Customers

TDS AEB2 MAGi(mA) (mA) (mA)

• 1.5V 250 (500)• 3.3V 300 (450) 1• 5V 80• +6V 170 11• -6V 90 11• +12V 7 52• -12V 7 28• +100V .3• -100V .3

Total 8 watts primary (10 hot)


Changes from one year ago

• Added MSKennedy regulators due to large current increases when hot– Changes in voltage losses in transformer, diodes, filter inductor

and CMC would have totaled .6V because of large current variations

– 1.9V linear regulator on 1.8V power to DCB (LNPS1)– 1.9V linear regulator on 1.8V power to DFB (LNPS1)– 1.5V linear regulator on 1.5V power to TDS (LNPS2)

• Moved +/-100V supply to its own transformer • SCM heater power switch moved from low side to high

side• Replaced Aeroflex UT16MX110 16 channel multiplexer

with an Intersil HS9-1840 for ease of use and reliability issues

• Eliminated three connectors from each– J06/J86 Preamp 1/3 heater line pass through– J07/J87 Preamp 2/4 heater line pass through– J08/J88 Preamp, SCM and MAG SCTemp lines


LNPS1_EM


LNPS2_EM


LNPS1 Block Diagram


LNPS2 Block Diagram


SYNC at 150 kHz

• Pre-Regulator and PWMs free run at 135kHz

• 600 kHz square wave clock– generated by DCB for LNPS1– generated by TDS for LNPS2

• Binary counter (HC4024) makes 150kHz for Pre-

Regulator and 300kHz for first PWM • Second and third (LNPS1 only) PWM slaved from the

first • All operate in sync from 16V to 40V input. • In the event of sync failure, all will free run whether

sync stops up, stops down, or is removed completely.


FET Testing and Selection

• Transformer drive FET selection was critical

• At 150kHz drain-source on resistance is not the most important

• Input capacitance, turn on delay time, rise time, turn off delay time, fall time are all important

• Tested 8 types of commercial International Rectifier FETs in LNPS breadboard

• Selected the IR rad-hard part that closest matched the specs of the one that was the most efficient

• JANSR2N7488T3 in a medium size TO-257AA package is efficient, runs cool and has a heat sink mounting tab.


POT Cores

• Ferroxcube pot cores are used for the transformers, filter inductors, and common mode chokes– Minnesota has used hundreds of these on dozens of projects– We have a standard procedure for their manufacture and

testing– They will be wound and assembled by the technician who has

made just about all of them

• Screening– Measure

• DC resistance of all windings• Inductance of all windings• Insulation resistance

– Check dielectric withstanding voltage– Perform temperature cycles and thermal shock– Repeat all measurements and reject any that changed beyond

specified limits


• 94% efficient in operating region

• 1 watt change causes only 1 mV change in output

(Graph is for LNPS1)

12V Pre-Regulator

Input watts at 30 Volts


LNPS2 Turn On Delay

• AEB +/-100V will be delayed from +5V by 100ms

• Top: 12V Pre-Regulator 10V/div

• Middle: 5V 2V/div

• Bottom: 100V 50V/div

• Time: 25 ms/div


Voltage Ripple

• 100mV peak spikes at 150kHz switching frequency

• 15mV – 20mV noise in between spikes

• DC-Low frequency noise will depend on the load variations of the various customers


LNPS1 Max and Min Voltage Specifications

Supply Max Min1.9V 1.90 Regulated 1.80 (after filter and CMC losses)3.3V 3.46 3.144V 4.20 3.805V 5.25 4.75+/-6 6.30 5.70+/-12 12.6 11.4+/-100 105 95- The numbers above are the specs. - The three +/- supplies have little load variation and I

will try to set them on the low side; i.e, 5.8, 11.8 and 98.

- The 3.3V has the largest load variation and therefore the entire 3.14 – 3.46 may be seen.

- Load resistors will keep no load voltages to reasonable values.


LNPS1 Temperatures Above Plate

Thermo-Vac performed at 60 and 70 C base plate


Low Voltage Turn 0n

• Turned on instrument in 1/3 volt increments from 0 to 28V • No evidence of a high current mode where two FETS were

on at the same time


In-rush current

• These photos are for LNPS2

• In-rush current will not be a problem

1 ms / div

0.5

am

ps

/ div

SPP Requirements

5 a

mps

/ div

25 ms / div


Coming up

• Finish load boxes for LNPS2

• Brief LNPS2 Thermo-Vac– Measure warm points with 60 and 70 C base plate

• Integrate LNPS2 with TDS

• Deliver LNPS2 to UCB (with TDS)

• Build second LNPS2

monsonpeer review – 5 december 2014 spp/fields lnps peer review steven monson university of...

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