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AN017 

1

 

Application Note 017 

 
 

MSK5031 Evaluation Board User's Guide 

By Bob Abel & Paul Musil, MSK; Revised 1/13/15 

 

 

 

Introduction 

 

The MSK5031 is a 200KHz to 2.4MHz step-down switching regulator controller with a high 
efficiency integrated switch. Synchronized or fixed high frequency switching coupled with 
wide input and output voltage ranges allows the designer to minimize the required board 
space for supporting components. With no load quiescent currents typically less than 100uA 
efficiency remains high at light loads. The shutdown circuitry allows the user to further 
reduce the input voltage supply current to less than 1uA. The MSK5031 is packaged in a 
hermetically sealed 16 pin flatpack and is available with a straight or gull wing lead form.  
 
The evaluation board provides a platform from which to evaluate new designs with ample 
real estate to make changes and evaluate results. Evaluation early in the design phase 
reduces the likelihood of excess ripple, instability, or other issues, from becoming a problem 
at the application PCB level. 
 
This application note is intended to be used in conjunction with the MSK5031 data sheet 
and the LT3480 data sheet. Reference those documents for additional application 
information and specifications. 
 

Setup 
 

Use the standard turret terminals to connect to your power supply and test equipment. 
Connect a power supply across the Vin and GND

1

 terminals (see note 1). Connect the output 

load between the VOUT and GND

2

 terminals. Use separate or Kelvin connections to 

connect input and output monitoring equipment. When measuring output ripple voltage with 
an oscilloscope probe, the wire from the probe to the ground clip will act as an antenna, 
picking up excessive noise. For improved results, the test hook should be removed from the 

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Summary of Contents for MSK5031

Page 1: ...om which to evaluate new designs with ample real estate to make changes and evaluate results Evaluation early in the design phase reduces the likelihood of excess ripple instability or other issues from becoming a problem at the application PCB level This application note is intended to be used in conjunction with the MSK5031 data sheet and the LT3480 data sheet Reference those documents for addit...

Page 2: ...ut Voltage Programming VOUT VFB 1 R1 R2 R1 R2 VOUT VFB 1 Given VREF 0 79V Typ Factory Configuration R1 8 98K R2 10 0K VOUT 0 79 1 8 98K 10 0K 1 499V Switching Frequency Programming The operating frequency is programmed by the value of RT The value for RT will vary from 187k at 200 kHz to 8 66k at 2 4 MHz based on the application requirements Higher operating frequencies require smaller inductor an...

Page 3: ... overall efficiency Connect a capacitor between Boost and SW to store a charge A boost pin voltage of at least 2 3V relative to the SW pin is required throughout the on time of the switch to guarantee that it remains saturated Capacitor C2 and an internal boost Schottky diode are used to generate a boost voltage that is higher than the input voltage In most cases a 0 22μF capacitor will work well ...

Page 4: ...sure that it is stable and tolerant of all these variations Phase margin and gain margin are measures of stability in closed loop systems Phase margin indicates relative stability and whether or not there is a tendency to oscillate during its damped response to an input change such as a step function Moreover the phase margin measures how much phase variation is needed at the gain crossover freque...

Page 5: ... setpoint Figure 3 A over damped The number of rings indicates the degree of stability and the frequency of the ringing shows the approximate unity gain frequency of the loop The amplitude of the signal is not particularly important as long as the amplitude is not so high that the loop behaves nonlinearly This method is easy to implement in labs not equipped with network analyzers but it does not ...

Page 6: ...he lowest synchronized frequency Reference the PGOOD pin description It is important to note that slope compensation is set by the RT value When the sync frequency is much higher than the one set by RT the slope compensation will be significantly reduced which may require a larger inductor value to prevent subharmonic oscillation PGOOD Pin The PGOOD pin is an open collector output driven by a comp...

Page 7: ...ESR by choosing a different capacitor or placing more capacitors in parallel For very low ripple an additional LC filter in the output may be a more suitable solution Re compensation of the loop may be required if the output capacitance is altered The output contains very narrow voltage spikes caused by the parasitic inductance of C5 Ceramic capacitors C6A and B remove these spikes on the demo boa...

Page 8: ...converter is limited by the maximum switch current rating This current rating is at least 3 5A for lower duty cycles and decreases linearly to 3 0A at a duty cycle of 0 8 for the MSK5031 Figure 5 Maximum output current is then reduced by one half peak to peak inductor current IMAX IP VOUT VIN VOUT 2 L f VIN Example given VOUT 5V VIN 8V DC 5 8 0 625 L 4 7µH IP 3 2A Figure 5 IMAX 3 2A 5V 8V 5V 2 4 7...

Page 9: ... Default Switching Frequency Vin 5 0V IOUT 1 0A kHz 781 Output Ripple Voltage Vin 5 0V IOUT 1 0A mVp p 7 Line Regulation 5V Vin 15V IOUT 1 0A 0 04 Load Regulation Vin 5 0V IOUT 5A to 2 0A 0 09 Efficiency Vin 5 0V IOUT 1 0A 72 4 Gain Margin Vin 5 0V IOUT 2 0A dB 32 4 Phase Margin Vin 5 0V IOUT 2 0A Deg 81 6 MSK5031 Evaluation Board PCB Layout Artwork Top Side Bottom Side ...

Page 10: ... C5B 47 uF Low ESR tantalum AVX TAZF476K010L CWR29FC476K C5C NP C5D NP C5E NP C5F NP C6A 1210 Ceramic cap 1 0uF AVX 12101C105K C6B 8050 Ceramic cap 0 1uF AVX 08051C104K C7 8050 Ceramic Cap 150pF AVX 08055A151K C8 8050 Ceramic Cap 0 015uF AVX 08055C153K C9 NP C10 NP C11 NP R1 Resistor 8 98K 1 8W R2 Resistor 10 0K 1 8W R3 Resistor 18 2K 1 8W R4 Resistor 20Ω 1 8W R5 Resistor 40 2K 1 8W R6 Resistor 49...

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