Analog Devices EVAL-LTC3313EV-A-Z Manual de usuario

User Guide | EVAL-LTC3313

UG-2077

Evaluating the LTC3313 5 V, 15 A Synchronous Step-Down Silent Switcher in 3 mm × 3 mm LQFN

PLEASE SEE THE LAST PAGE FOR AN IMPORTANT

WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | 1 of 11

FEATURES

►EVAL-LTC3313EV-A-Z evaluation board

►Transient circuit included for load transient evaluation

►EMI filter included to reduce noise in EMI emission tests

►MODE pin pull-up option for pulse-skipping mode evaluation

EVALUATION KIT CONTENTS

►EVAL-LTC3313EV-A-Z evaluation board

DOCUMENTS NEEDED

►LTC3313 data sheet

►EVAL-LTC3313EV-A-Z user guide

EQUIPMENT NEEDED

►A DC voltage source

►An electronic load

►A multimeter

EVALUATION BOARD PHOTOGRAPH

Figure 1. EVAL-LTC3313EV-A-Z Board Photograph

GENERAL DESCRIPTION

The EVAL-LTC3313EV-A-Z features the LTC3313, 15 A low voltage

synchronous step-down Silent Switcher® that operates as a 2 MHz,

2.25 V to 5.5 V input, 1.2 V, 15 A output buck regulator. The

LTC3313 supports an output voltage (VOUT) from 0.5 V to the input

voltage (VIN) with operating frequencies from 500 kHz up to 5 MHz.

The LTC3313 is a compact, ultralow emission, high-efficiency, and

high speed synchronous monolithic step-down switching regulator.

The Silent Switcher technology optimizes fast-current loops and

makes it easier to minimize electromagnetic interference (EMI)

and electromagnetic compatibility (EMC) emissions. The minimum

on-time of 35 ns typical enables high VIN to low VOUT conversion at

a high frequency.

The EVAL-LTC3313EV-A-Z runs in forced continuous mode with a

2 MHz switching frequency (fSW); however, it can be configured to

run at different switching frequencies or in pulse-skipping mode.

The LTC3313 oscillator can also synchronize to an external clock

using a MODE/SYNC turret, with the EVAL-LTC3313EV-A-Z default

setup. Figure 4 shows the efficiency and power loss of the EVAL-

LTC3313EV-A-Z with a 3.3 V input in both operation modes.

The EVAL-LTC3313EV-A-Z also has an EMI filter to reduce con-

ducted EMI. This EMI filter can be included by applying the input

voltage at the VIN EMI terminal. The EMI performance of the board-

EVAL-LTC3313EV-A-Z is shown in the EMI Test Results section.

The red lines in the EMI performance graphs illustrate the CISPR25

Class 5 peak limits for the conducted and radiated emission tests.

The LTC3313 data sheet gives a complete description of the device

and its application information. The data sheet must be read in

conjunction with this evaluation board user guide. The LTC3313 is

assembled in a 3 mm × 3 mm LQFN package with an exposed

pad for low thermal resistance. The layout recommendations for low

EMI operation and maximum thermal performance are available in

the LTC3313 data sheet.

User Guide EVAL-LTC3313

TABLE OF CONTENTS

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Features................................................................ 1

Evaluation Kit Contents......................................... 1

Documents Needed...............................................1

Equipment Needed................................................1

Evaluation Board Photograph................................1

General Description...............................................1

Performance Summary..........................................3

Evaluation Board Hardware...................................4

Introduction to the EVAL-LTC3313EV-A-Z......... 4

Quick Start Procedure........................................... 5

Typical Performance Characteristics..................... 6

Test Setup..............................................................7

EMI Test Results....................................................8

Evaluation Board Schematic................................. 9

Ordering Information............................................10

Bill of Materials.................................................10

REVISION HISTORY

1/2023—Revision 0: Initial Version

User Guide EVAL-LTC3313

PERFORMANCE SUMMARY

analog.com Rev. 0 | 3 of 11

TA = 25°C.

Table 1. Performance Summary

Parameter Test Conditions/Comments Min Typ Max Unit

VIN/VIN EMI 2.25 5.5 V

VOUT 1.176 1.200 1.224 V

Output Current, IOUT 15 A

fSW 1.8 2 2.2 MHz

Efficiency VIN = 3.3 V, IOUT = 5 A 92.5 %

User Guide EVAL-LTC3313

EVALUATION BOARD HARDWARE

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INTRODUCTION TO THE EVAL-LTC3313EV-A-Z

The EVAL-LTC3313EV-A-Z evaluation board features the LTC3313,

a low voltage, synchronous step-down Silent Switcher. The

LTC3313 is a monolithic, constant frequency, current mode step-

down DC/DC converter. An oscillator turns on the internal top power

switch at the beginning of each clock cycle. Current in the inductor

then increases until the top switch comparator trips and turns off

the top power switch. The peak inductor current, at which the top

switch turns off, is controlled by the voltage on the ITH node.

The error amplifier servos the ITH pin by comparing the voltage

on the internal VFB pin with an internal 500 mV reference. When

the load current increases, it causes a reduction in the feedback

voltage relative to the reference, leading the error amplifier to raise

the ITH voltage until the average inductor current matches the

new load current. When the top switch turns off, the synchronous

bottom power switch turns on until the next clock cycle begins. In

pulse-skipping mode, the bottom switch also turns off when inductor

current falls to zero. If overload conditions result in excessive

current flowing through the bottom switch, the next clock cycle will

be delayed until the switch current returns to a safe level.

If the EN pin is low, the LTC3313 is in a shutdown state with a low

quiescent current. When the EN pin is more than its threshold, the

switching regulator enables.

The MODE/SYNC pin synchronizes the switching frequency to an

external clock that can be a clock output for multiphase operation.

The MODE/SYNC pin also sets the regulator operation modes. The

operation modes are either forced continuous or pulse-skipping.

See the LTC3313 data sheet for more detailed information.

The maximum allowable operating frequency (fSW(MAX)) is influ-

enced by the minimum on time (tON(MIN)) of the top switch, the ratio

of VOUT to VIN and the inductance of the output inductor. Use the

following equation to calculate the maximum allowable operating

frequency:

fSW MAX =VOUT

VIN MAX ×tON MIN

(1)

Select an operating switching frequency below fSW(MAX). It is de-

sired to obtain an inductor current of 30% of the maximum LTC3313

operating load, 15 A. Use the following equations to calculate

the inductor value to obtain a 30% (4.5 A) inductor ripple for the

operating frequency:

L ≥ VOUT

3.75A × fSW ×1−VOUT

VIN MAX 

for VOUT

VIN MAX ≤0 . 5

(2)

L ≥ 0 . 25 × VIN MAX

3.75A × fSW for VOUT

VIN MAX > 0 . 5

(3)

When determining the compensation components, C4, C10, C24,

and R12, controlling the loop stability and transient response are

the two main considerations. The LTC3313 was designed to oper-

ate at a high bandwidth for fast transient response capabilities,

which reduces the required output capacitance to meet the desired

transient voltage range. The midband gain of the loop increases

with R12 and the bandwidth of the loop increases by decreasing

C24. C4 and R9 provide a phase lead that improves the phase

margin. C10 and R12 provide a high-frequency pole to reduce the

high-frequency gain.

Loop stability is generally measured using the Bode plot method

of plotting loop gain in decibels and phase shift in degrees. The

0 dB crossover frequency must be less than 1/6 of the operating

frequency to reduce the effects of the added phase shift of the

modulator. The control-loop phase margin goal must be 45º or

greater, and the gain margin goal must be 8 dB or greater.

Figure 2. LTC3313, 1.2 V/15 A Step-Down Converter Typical Solution

User Guide EVAL-LTC3313

QUICK START PROCEDURE

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Before following the quick start procedure, note that for accurate

VIN, VOUT, and efficiency measurements, measure VIN at the VIN

SNSE and GND SNSN turrets and measure VOUT at the VOUT

SNSE and GND SNSE turrets, which are illustrated as VM1 and

VM2 in Figure 6. In addition, when measuring the input or output

ripple, avoid a long ground lead on the oscilloscope probe.

Refer to Figure 6 for the proper measurement equipment test setup

and also take the following steps:

1. Set the JP1 jumper to the HI position.

2. With power off, connect the input power supply to VIN and GND.

If the input EMI filter is desired, connect the input power supply

to VIN EMI and GND.

3. Set the power supply (PS1) current limit to 10 A.

4. Set the electronic load (LD1) to CC mode and a 0 A current.

5. Slowly increase PS1 to 1.0 V. If the PS1 output current reads

less than 20 mA, increase PS1 to 3.3 V.

6. Verify that VM1 reads 3.3 V and that VM2 reads approximately

1.2 V.

7. Check VM1, VM2, VM3, the PS1 output current, and the LD1

input current.

8. Connect an oscilloscope voltage probe as shown in Figure 7 or

Figure 8.

9. Set the channel to AC-coupled, the voltage scale to 20 mV, and

the time base to 10 µs. Also, check the VOUT ripple and verify

that the PGOOD voltage is more than 3 V.

10. Increase the load by 1 A intervals up to 15 A and observe the

voltage output regulation, ripple voltage, and the voltage on the

SSTT turret.

11. Use the following equation to calculate the die temperature:

TJ°C=VSSTT

4mV −273

(4)

12. If pulse-skipping mode is desired, set PS1 to 0 V, install a 0

Ω resistor in the R3 location, and remove R6. Repeat Step

1 through Step 11. In step 11, observe that the switching

waveform is now in pulse-skipping mode at light load.

13. Optionally, to change the frequency, remove R3 and R4, if

installed. Install the desired RT resistor in the R7 location. Note

that the MODE/SYNC pin must have high impedance to GND

and VIN. Size the inductor, output capacitors, and compensation

components to provide the desired inductor ripple and a stable

output. Refer to the LTC3313 data sheet and LTpowerCAD for

more information on choosing the required components.

14. To test the transient response with a base load, add the desired

resistor to produce a minimum load between the VOUT and the

I_STEP turrets (RL shown on Figure 6). Note that the total load

resistance is RL + R14 (20 mΩ). Adjust a signal generator with

a 10 ms period, a 10% duty cycle, and an amplitude from 1 V to

2 V to start.

15. Measure the I_STEP voltage to observe the current, VI_STEP /20

mΩ. Adjust the amplitude of the pulse to provide the desired

transient. Connect the signal generator (SG_INPUT) between

the SG_INPUT and GND turrets. Adjust the rising and falling

edge of the pulse to provide the desired ramp rate. Figure 5

shows a load step from 5 A to 10 A. Refer to the following

equations:

IOUT =VI_STEP

20mΩ

(5)

VGS =VSG_INPUT − VI_STEP

(6)

16. When done, turn off SG_INPUT, PS1, and the load, and remove

all the connections to the EVAL-LTC3313EV-A-Z.

User Guide EVAL-LTC3313

TYPICAL PERFORMANCE CHARACTERISTICS

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Figure 3. Start-Up Waveforms with Light Load (ILOAD Is the Load Inductance.)

Figure 4. Efficiency vs. Load Current

Figure 5. Load Step Response

User Guide EVAL-LTC3313

TEST SETUP

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Figure 6. Test Setup for EVAL-LTC3313EV-A-Z

Figure 7. Technique for Measuring Output Ripple and Step Response with a Scope Probe

Figure 8. Technique for Measuring Output Ripple and Step Response with a Low Inductance Connector (Not Supplied)

User Guide EVAL-LTC3313

EMI TEST RESULTS

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Figure 9. EVAL-LTC3313EV-A-Z CISPR25 Conducted Emission with Class 5

Peak Limits (Voltage Method)

Figure 10. EVAL-LTC3313EV-A-Z CISPR25 Radiated Emission (Horizontal)

Figure 11. EVAL-LTC3313EV-A-Z CISPR25 Radiated Emission (Vertical)

User Guide EVAL-LTC3313

EVALUATION BOARD SCHEMATIC

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Figure 12. EVAL-LTC3313EV-A-Z Evaluation Board Schematic

User Guide EVAL-LTC3313

ORDERING INFORMATION

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BILL OF MATERIALS

Table 2. Bill of Materials

Quantity Circuit Component Description Manufacturer/Part Number

Required

4 C2, C3, C21, C22 10 μF ceramic capacitors, 6.3 V, 20%, X7S, 0603, low

effective series resistance (ESR)

TDK, C1608X7S0J106M080AC

1 C4 47 pF ceramic capacitor, 50 V, 5%, C0G, 0402, AEC-

Q200

Murata, GCM1555C1H470JA16D

2 C5, C6 47 μF capacitors, X7S, 6.3 V, 20%,1206 TDK, C3216X7S0J476M160AC

3 C8, C19, C20 1 μF ceramic capacitors, 6.3 V, 20%, X7T, 0201 Murata, GRM033D70J105ME01D

1 C9 0.033 μF ceramic capacitor, 25 V, 10%, X7R, 0402,

AEC-Q200

Murata, GCM155R71E333KA55D

1 C12 2.2 μF ceramic capacitor, 10 V, 10%, X7S, 0402,

AEC-Q200

Murata, GRT155C71A225KE13D

1 C24 470 pF ceramic capacitor, 50 V, 5%, C0G, 0402 Murata, GRM1555C1H471JA01D

1 L1 0.08 μH inductor, power shielded, 20%, AEC-Q200 Coilcraft, XEL4020-800MEC

1 R9 140 kΩ resistor, surface-mounted device (SMD), 1%,

1/16 W, 0402, AEC-Q200

Vishay, CRCW0402140KFKED

1 R10 100 kΩ resistor, SMD, 1%, 1/10 W, 0402, AEC-Q200 Panasonic, ERJ-2RKF1003X

1 R12 4.99 kΩ resistor, SMD, 1%, 1/10 W, 0402, AEC-Q200 Panasonic, ERJ-2RKF4991X

1 U1 5 V, 15 A, synchronous step-down Silent Switcher in

3 mm x 3 mm LQFN

Analog Devices, Inc., LTC3313EV#PBF

Additional

2 C1, C18 470 μF tantalum capacitors, 6.3 V, 20%, 7343-40,

very low ESR, 0.005 Ω

Kemet, T530Y477M006ATE005

2 C7, C15 0.1 μF ceramic capacitors, 16 V, 10%, X7R, 0402,

AEC-Q200

Murata, GCM155R71C104KA55D

1 C11 0.1 μF ceramic capacitor, 50 V, 10%, X7R, 0402,

AEC-Q200, low ESR

TDK, CGA2B3X7R1H104K050BB

4 C13, C14, C16, C17 10 μF ceramic capacitors, 6.3 V, 20%, X7R, 0603 Samsung, CL10B106MQ8NRNC

2 C25, C26 0.22 μF ceramic capacitors, 6.3 V, 20%, X7R, 0603,

feed through

Johanson Dielectrics, 6R3X14W224MV4T

2 C27, C28 10 μF ceramic capacitors, 6.3 V, 20%, X7S, 0603, low

ESR

TDK, C1608X7S0J106M080AC

1 C29 2.2 μF ceramic capacitor, 10 V, 10%, X7S, 0402,

AEC-Q200

Murata, GRT155C71A225KE13D

1 L2 Inductor, EMI, ferrite bead, 8 A Wurth Elektronik, 74279226101

1 Q1 Transistor, metal-oxide semiconductor field-effect

transistor (MOSFET), N channel, 25 V, 38 A, 8-lead

TDSON, EP

Infineon, BSC010NE2LSIATMA1

1 R1 1 MΩ resistor, SMD, 1%, 1/16 W, 0402, AEC-Q200 Vishay, CRCW04021M00FKED

1 R2 249 kΩ resistor, SMD, 1%, 1/16 W, 0402, AEC-Q200 Stackpole, RMCF0402FT249K

1 R4 0 Ω resistor, SMD, jumper, 1/10 W, 0402, AEC-Q200 Panasonic, ERJ-2GE0R00X

2 R6, R11 100 kΩ resistors, SMD, 5%, 1/16 W, 0402, AEC-Q200 Vishay, CRCW0402100KJNED

1 R8 20 Ω resistor, SMD, 1%, 1/10 W, 0402, AEC-Q200 Panasonic, ERJ-2RKF20R0X

1 R14 0.02 Ω resistor, SMD, 1%, 10 W, 2818, AEC-Q200 Vishay, WSHP2818R0200FEA

1 R15 10 kΩ resistor, SMD, 5%, 1/16 W, 0402, AEC-Q200 Vishay, CRCW040210K0JNED

1 J1 Connector, U.FL, receptor, straight, SMD, 0 Hz to 6

GHz, 50 Ω

Hirose Electric, U.FL-R-SMT-1(10)

Required Hardware

11 TP1 to TP3, TP5, TP12, TP14 to TP17,

TP20, TP21

Printed circuit board (PCB) connectors, solder

terminal turrets for clip leads

Mill-Max, 2308-2-00-80-00-00-07-0

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