1. Radar Interface Design Project Critical Design Review Sponsor: Scott Faulkner, Lockheed Martin
Group #1 Catherine Donoso Diego Rocha Keith Weston

2. Overview Lockheed Martin sponsored project
Advisor is RF Engineer, Scott Faulkner
Power Supply (PS) for transceiver in Joint Air to Ground Missile (JAGM) seeker
PS must include control unit
PS system must generate specific voltages
PS system must use power sequencing

3. Goals
Provide solutions to the next generation transceiver power supply design flaws by using innovative ideas
Low EMI
Low thermal characteristics
Smaller circuit card than used before
Find alternative parts utilizing new technology
Provide FPGA loads for future use

4. Requirements Lowest EMI possible Lowest possible power
No heat sink available directly on board, only for system
limited airflow
Preferrable non-Rohs Compliant

5. Specifications 32V, 1.5V and 3.3V provided
3W dissipation for each part
Preferable military grade temperature, -55 to +125
6 sq. in board, any shape
High power architecture
+6V
load- less than 50% duty cycle and applied no longer than 100us
pulse repetition rate from 1 to 100 kHz
Low power architecture
load-continuous
-4V, +6V, +9V
FPGA
Power sequencing--4V,+6,+9,+6(high)
Signal
Output Voltage
Output Current
Regulation
Ripple Voltage
6XMIT
6VDC
11 A 3%
1mV
9XCVR
+9VDC
100mA
100uV
6XCVR
+6VDC
1000mA
4XCVR
-4VDC
250mA

6. Power Sequence Power UP sequence -4V, +6V(low), +9V, +6V(High)
exact opposite for power down
SWPS for both high power and low power uses PGOOD pin to send high or low signal to FPGA
FPGA will send signal at least 2.5V to RUN pin to turn ON/OFF SWPS
LDO and charge pump send Vout signal to ADC onboard FPGA
FPGA will send signal to pull up or down SHDN pin to turn ON/OFF parts, must use pull-up resistor. probably transistor for switch
Failure Mode
FPGA must power down all power supplies in exact opposite order

7. Noise Consideration and Solution
Power supply to transceiver must have clean signal as to avoid possible malfunction because of noise
Must use low noise parts
Difficult to use low noise parts in a power supply-many parts use switching to step-down voltage
Challenge-avoid noisy parts or isolate noisy parts from transceiver
Use filtering
Use mu-metal for magnetic shielding

8. Temperature Consideration
Tjamax = 150 degrees celsius
Tamax = 59 degrees celsius (found from voltage values given max. Tjamax)
[Iout*(Vin-Vout)] + (Ignd)Vin Ignd can be found from the graph below.
Very important to narrow the delta between Vin and Vout. SWPS needs step-down voltage as much as possible
SWPS heat dissipation not as severe as LDO

9. Low Power Design SWPS: LTM8032 was LTM4612 low noise
smaller than other models
handles large step-down delta
LDO: LTM1963
heat dissipation
used as filter
Charge pump: LT1054
was LT3704 and ripple attenuator
inverts
steps down
small
least noisy of power supplies that invert

10. Simulation and Experimental Noise Results
SA proved low noise for SWPS,8032
LTSpice Simulation proved no noise for LDO
LDO useful as a filter

11. Board Space Consideration and Challenge
Only 6 sq. in., or 3850 sq. mm. in rectangular shape
Power supply requires multiple parts for proper function
Now, main parts occupy 2950 sq. mm.
Parts will be installed only on topside
Est. # of layers is 5-6
A couple signal layers will be needed to support amount of traces on small surface area for large # of parts
What can be eliminated? Replaced?
Part #
Amount Used
Area
Total Area
LTM 4612 4
675
2700
LT1963 2
65.28
130.56
HMC-VVD104 1
LTC3704
Fusion
100
TOTAL AREA
2950

12. Proving the Design
Will not be installed in missile seeker, therefore needs to be proven to work outside of actual system
Mock loads must be created to effectively test power supply
High power architecture will have separate test card
Prototype only purpose, test card will be implemented on same board
Low power architecture will have onboard test card
Logic analyzer used to time power sequence

13. High Power Section Process power as required by the load.
Efficiency must fit in the 90 percentile range.
Meet power sequencing.
Meet EMI requirements.
Testing prototype to debug and prove its functionality.

14. 6XMIT Power Supply
6XMIT will drive the transceiver with load durations ranging from 1k Hz to 100k Hz with a duty cycle no greater than 50%.
6XMIT 6 11 Amps peak 3% Regulation 1 mV noise.
Implementation of DC/DC converters turns out to be a must in order to meet specs.

15. LT uModule Family
To facilitate switching power supply Linear Technology has designed 8 dc/dc uModules.
LGA package for these family has been designed with very low thermal resistance thus increasing heat dissipation.
The ultralow noise design has the lowest EMI for DC/DC converter modules.

16. LTM4612 5V to 36 V input voltage range. 5A DC, 7A peak output current.
Parallel/ Current sharing
Voltage and current protection
Programmable soft-start

17. Efficiency
Theoretically dc/dc converters are capable of achieving 100 % efficiency.
The LTM4612 ultra-low noise dc/dc buck converter can achieve efficiencies up to 92 %.

18. Paralleling LTM4612 Polyphase configuration lowers ripple.
Spreading the spectrum lowers EMI
Current sharing allows converters to be paralleled

19. Spreading Spectrum Frequency Spectrum using technique
Frequency Spectrum without using technique

20. Testing Prototype TI 2808 DSP
Familiarity with 2808 DSP board facilitates test set up.
PWM pins have been coded to generate waveforms that can range between 1kHz to 100kHz with a duty cycle that can be varied from 0 to 50%.
200kW resistor load bank available for testing.

21. Test set up