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SPP/FIELDS LNPS PEER REVIEW

SPP/FIELDS LNPS PEER REVIEW. Steven Monson University of Minnesota monson@waves.space.umn.edu. 3D View of Main Electronics Package. SPP FIELDS Instrument Block Diagram. LNPS Requirements. O perate from 22 to 35 VDC Operate over the range of -25 to +65 degrees C base plate temperature

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SPP/FIELDS LNPS PEER REVIEW

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  1. SPP/FIELDS LNPSPEER REVIEW Steven Monson University of Minnesota monson@waves.space.umn.edu

  2. 3D View of Main Electronics Package

  3. SPP FIELDS Instrument Block Diagram

  4. LNPS Requirements • Operate from 22 to 35 VDC • Operate over the range of -25 to +65 degrees C base plate temperature • Must sync at 150 kHz but operate nominally without sync • Provide ten DC voltage supplies • 1.8V, 3.3V, 4V, 5V, +/- 6V, +/- 12V, +/- 100V • +/-100V supply to be delayed by 100ms from 5V supply (AEB) • Total secondary power to be approx. 7w for LNPS1 and 4w for LNPS2 • Monitor and multiplex 10 voltages, LNPS temp and one SCM temp • Provide sense circuit and control for SCM heater • Provide pass through of some additional lines • Primary heater power for MAG and Preamps • Temperature feedback for MAG and Preamps

  5. Comparison • STEREO/WAVES SPP/FIELDS 15 watts primary 11 watts primary LNPS1 (14w hot) 7 watts primary LNPS2 (9w hot) 100 kHz 150 kHz LTC1149 switching regulator MSKennedy 5055RH (plastic) (LT3845A rad hard dice) HS1825ARH pulse width modulator same 25 degree C 55 degree C

  6. LNPS Block Diagram

  7. LNPS1 Customers DCB RFS DFB AEB SCM MAG (mA) (mA) (mA) (mA) (mA) (mA) • 1.8V 250 (500) 364 (728) • 3.3V 300 (450) 285 (428) 1 • 4V 170 • 5V 150 • +6V 41 24 12 • -6V 41 19 12 • +12V 4 11 12 52 • -12V 4 11 12 28 • +100V .5 • -100V .5 Total 11.3 watts primary (14.5 hot)

  8. LNPS2 Customers TDS AEB2 MAG (mA) (mA) (mA) • 1.8V 250 (500) • 3.3V 300 (450) 1 • 5V 111 • +6V 6012 • -6V 60 12 • +12V 7 52 • -12V 7 28 • +100V .3 • -100V .3 Total 6.7 watts primary (8.3 hot)

  9. Risk - High Currents When Hot • The current LNPS design does not have enough margin to accommodate the doubling of FPGA power when hot • Could add more transformers • Add two transformers dividing 1.8V and 3.3V into two each • Would take a lot more space for two extra transformers and associated diodes and filters. • Separates DCB and DFB supplies (positive) • I have never ran three transformers off of one pair of FETs • FETs would need to be larger also • May be better to go to third PWM (take even more board space) • Board space will not be known for a couple more weeks • Could make transformers larger • Would increase box height by about .15 inches • Would take more space but not as much as above • Are high temperature predictions correct?

  10. 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 PWM slaved from the first • All 3 operate in sync from 16V to 40V input. • In the event of sync failure, all 3 free run at 135kHz whether sync stops up, stops down, or is removed completely.

  11. 12V Pre-Regulator • 95% efficient at 11 watts • 1 watt change causes only 1 mV change in output

  12. 1.8V / 3.3V Voltage Variations • FPGA currents will go up when hot (LNPS1) • 614 mA could go to 1228 mA for 1.8V supply • Transformer output will drop .1V • Two diode drops will decrease output .25V • Filter inductor looses .05V • CMC for +V and RTN drops another .24V • Total change could be .64V • Need 1.84V minimum • Will need 2.48V out of transformer for quiet room-temperature conditions • Can we eliminate CMCs on the 1.8V and 3.3V supplies?

  13. Turn On Delay • Flight instrument will have AEB +/-100V delayed from +5V by 100ms • Top: 12V Pre-Regulator 10V/div • Middle: 3.3V 2V/div • Comes from first PWM • Bottom: 4V 2V/div • Comes from 2nd PWM • Time: 25 ms/div

  14. Voltage Ripple • Not able to measure until we have a working EM in box • Will depend on how much loads vary • Measurements from STEREO/WAVES of complete operating instrument with true RMS meter (300kHz bandwidth): • 12V Pre-Regulator 25 mV • +/- 8V 20mV • +5V 30 mV • +5V DPU 100 mV

  15. Tested a breadboard with the Pre-regulator and both PWMs 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 Low Voltage Turn 0n

  16. Inrush current SPP Requirements STEREO/WAVES 1 amp / div 1 ms/ div • SPP has same specs as STEREO • SPP/FIELDS will be very similarto STEREO/WAVES which was well within spec • 100ms delay of 2nd PWM will lower first spike and make a second smaller peak at 100ms

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