EN5337QI-E - ENPIRION - Datasheet.Live

EN5337QI Evaluation Board Application Note

August 2008 V1.0

Enpirion EN5337QI 3A DCDC Converter

w/Integrated Inductor Evaluation Board

Introduction

Thank you for choosing Enpirion, the source for Ultra small foot print power

converter products!

• The EN5337QI features integrated inductor, power MOSFETS, Controller,

a bulk of the compensation Network, and protection circuitry against

system faults. This level of integration delivers a substantial reduction in

footprint and part count over competing solutions. However, the evaluation

board is not optimized for minimum footprint; rather for engineering ease

of evaluation through programming options, clip leads, test points etc.

• The EN5337QI features a customer programmable output voltage by

means of a resistor divider. The resistor divider allows the user to set the

output voltage to any value within the range 0.75V to (VIN-VDROPOUT). The

evaluation board, as shipped is populated with a 4 resistor divider option.

The upper resistor is fixed (150kΩ) and has a phase lead capacitor (27pF)

in parallel. One of 4 lower resistors is selected with the jumper option for

output voltages of 1.0V, 1.2V, 1.55V and 2.5V. We recommend the user to

retain the upper resistor and capacitor values and change only the lower

resistor to program the output to the desired voltage.

• This device has no over-voltage protection feature. We strongly

recommend the customer to ensure the feedback loop is truly closed

before powering up the device especially if the load can not withstand the

input voltage.

• The input capacitor is a 10V rated 2X10uF X5R MLCC. The output filter

section is populated with 1 x 10uF and 1 x 47uF, 6.3V rated X5R MLC

capacitors to achieve the required ~50uF of output capacitance. This

combination of output caps yields very low ESR and hence low output

ripple. A single 47uF capacitor may be substituted if minimizing footprint

is important. The Soft-start capacitor is a small 10V rated 15nF X5R

MLCC.

• Pads are available to add an additional input capacitor and there are a

total of 5 pads to accommodate the output capacitor(s). This allows for

evaluation of performance over a wide range of input/output capacitor

combinations.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

• Clip on terminals are provided for ENA, SS, POK, VIN and VOUT. Other

test points are also made available.

• A jumper is provided for controlling the Enable signal. Enable may also be

controlled using an external switching source by removing the jumper and

applying the enable signal to the middle pin and ground.

• A jumper is also provided to connect a resistor load to POK pin. This

jumper is especially useful to measure the disable current and eliminates

having to subtract the current drawn by this load.

• Foot print is also provided for a SMA connector to SYNC input. The SYNC

input allows the device switching to be phase locked to an external clock

signal. This external clock synchronization allows for moving any offending

beat frequency to be moved out-of-band. A swept frequency applied to this

pin results in spread spectrum operation and reduces the peaks in the

noise spectrum of emitted EMI.

• Numerous test points are provided as well as banana plugs for input and

output connections. Input / Output ripple are best measured at test points

J12 / J11. The switching waveform may be viewed between test points

labeled SW and GND.

• The board comes with input decoupling and reverse polarity protection to

guard the device against common setup mishaps.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

Quick Start Guide

of the

Figure 1 shows a top view evaluation board.

WARNING: complete steps 1 through 4 before applying power to the

EN5337QI evaluation board.

STEP 1: Set the “ENABLE” jumper to the Disable Position.

Figure 2: Shows POK & Enable Jumpers Disable

Position

(POK jumper as shown connects pull-up resistor to VIN.

Enable jumper shown in DISABLE position.)

STEP 2: Connect Power Supply to the input power connectors, VIN (+) and

GND (-) as indicated in Figure 1 and set the supply to the desired voltage. The

device disable current may be measured in this configuration.

CAUTION: be mindful of the polarity. Even though the evaluation board

comes with reverse polarity protection diodes, it is rarely a good idea to

reverse the input polarity.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

STEP 3: Connect the load to the output connectors VOUT (+) and GND (-), as

indicated in Figure 1.

STEP 4: Select the output voltage setting jumper. You may also set the POK

jumper to include the POK load if POK signal monitoring is intended. The only

time to disable POK is when measuring the absolute Disable current.

Figure 3: Output Voltage selection jumpers

Jumper shown selects 1.2V output

(Jumper positions from left are: 2.5V, 1.55V, 1.0V and 1.2V)

STEP 5: Apply VIN to the board and move the ENABLE jumper to the enabled

position. The EN5337QI is now powered up! Various measurements such as

efficiency, line and load regulation, input / output ripple, load transient, drop-out

voltage measurements may be made at this point. The over current trip level,

short circuit protection, under voltage lock out thresholds, temperature coefficient

of the output voltage may also be measured in this configuration.

STEP 5A: Power Up/Down Behavior – Remove ENA jumper and connect a

pulse generator (output disabled) signal to the middle pin of ENA and Ground.

Set the pulse amplitude to swing from 0 to 2.5 volts. Set the pulse period to

10msec. and duty cycle to 50%. Hook up oscilloscope probes to ENA, SS, POK

and VOUT with clean ground returns. Apply power to evaluation board. Enable

pulse generator output. Observe the SS capacitor and VOUT voltage ramps as

ENA goes high and again as ENA goes low. The device when powered down

ramps down the output voltage in a controlled manner before fully shutting down.

The output voltage level when POK is asserted /de-asserted as the device is

powered up / down may be observed as well as the clean output voltage ramp

and POK signals.

GND

Ext. Enable

Figure 4: Means to Pulse Enable

STEP 6: External Clock Synchronization / Spread Spectrum Modes: In order

to activate this mode, it may be necessary to a solder a SMA connector at J8.

Alternately the input clock signal leads may be directly soldered to the through

holes of J8 as shown below.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

GND

Ext. Clock

Figure 4: SMA Connector for External Clock Input

Power down the device. Move ENA into disable position. Connect the clock

signal as just indicated. The clock signal should be clean and have a frequency in

the range of 4.5 to 5.5MHz; amplitude 0 to 2.5 volts with a duty cycle between 20

and 80%.

With SYNC signal disabled, power up the device and move ENA jumper to

Enabled position. The device is now powered up and outputting the desired

voltage. The device is switching at its free running frequency. The switching

waveform may be observed between test points SW and GND. Now enabling the

SYNC signal will automatically phase lock the internal switching frequency to the

externally applied frequency as long as the external clock parameters are within

the specified range. To observe phase-lock connect oscilloscope probes to the

input clock as well as to the SW test point. Phase lock range can be determined

by sweeping the external clock frequency up / down until the device just goes out

of lock at the two extremes of its range.

For spread spectrum operation the input clock frequency may be swept between

two frequencies that are within the lock range. The sweep (jitter) frequency

should be limited to 10kHz. The radiated EMI spectrum may be now measured in

various states – free running, phase locked to a fixed frequency and spread

spectrum.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

C10

TP4

C11

J10

TP5

0805

TP3

TP2

J11

J12

C12

0402

TP17

TP18

TP17 & TP18 are

used for special

testing. They are

not labeled on PCB.

PVIN FB1

GND OUT GND IN

C13

TP12

TP15

TP6TP7

TP13

TP14

POK

AVIN

ENA

TP8

TP9TP10

TP11

TP16

POK

ENA

VOUT

VIN

U2 D1

PVIN

VOUT

Add short across R6

when all other

routing is completed

C16 J13

C17

J14

XFB

EAOUT

XFB EAOUT

EN5337Q

NC(SW)

NC3

NC4

VOUT

NC(SW)

PGND

VIN

PGND 25

VDDB 24

BTMP 23

PG 22

VIN 21

VIN 20

NC(SW) 38

NC(SW) 37

NC(SW) 36

NC(SW) 35

NC(SW) 34

AVIN 33

AGND 32

XFB 31

SS 30

EAOUT 29

POK 28

ENA 27

SYNC 26

R8 C14

C15

0805

1206/0805

0805

1206/0805

1206

SYNC

1206/0805

TP1

0402

Figure 5: EN5337 Evaluation Board Schematic

Output Voltage Select

Programming the Output Voltage.

The EN5337QI output voltage is programmed using a simple resistor divider

network. Figure 6 shows a schematic view of the resistor divider configuration.

The EN5337QI output voltage is determined by the voltage presented at the XFB

pin. The voltage is set by way of a resistor divider between VOUT and AGND with

the midpoint going to XFB. A phase lead capacitor is also required across the

upper resistor – the one between VOUT and XFB.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

XFB

CSS

VOUT

POK

PGNDAGND

PVIN

AVIN

VOUT

VIN

22µF~50uF

Figure 6: VOUT resistor divider network and Phase lead Details.

RA =150kΩ, CA = 27pF

)75.0( *75.0 VVOUT RAV

RB −

Test Recommendations

Recommendations

To guarantee measurement accuracy, the following precautions should be

observed:

1. Make all input and output voltage measurements at the board using the

test points provided. This will eliminate voltage drop across the line and

load cables that can produce false readings.

2. Measure input and output current with series ammeters or accurate

shunt resistors. This is especially important when measuring efficiency.

3. Use a balanced impedance probe tip to measure switching signals to

avoid noise coupling into the probe ground lead. Output ripple and load

transient deviation are best measured at J11.

4. The board includes a 5.6k pull-up for the POK signal and ready to

monitor the power OK status. The POK signal may be viewed at clip

lead marked POK.

5. A 15nF soft-start capacitor is populated on the board for ~1msec soft-

start time.

6. The over-current protection circuit typically limits the maximum load

current to approximately 1.5X the rated value – viz. 4.5A.

7. DERATING: The evaluation board may not be operated with maximum

power dissipation (input power – output power) beyond a certain

temperature (see derating graph.) for extended periods of time. The

device will shut down when the internal junction temperature exceeds

~150°C.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

Input and Output Capacitors

The input capacitance requirement is 2X10uF for the EN5337QI. Enpirion

recommends that a low ESR MLC capacitor be used. The voltage rating should

rated high enough to provide adequate margin for your application. There is a

pre-tinned pad for one additional 1210 capacitor to experiment with input filter

performance.

The output capacitance requirement is approximately 50uF of capacitance. The

EN5337QI-E evaluation board comes populated with 1 x 10uF 0805 and 1 x

47uF 1206, 6.3V MLC capacitors. The 2 parallel capacitors provide reduced ESR

and hence lower output ripple voltage. If a minimum footprint configuration is

desired, a single 47uF MLC capacitor can be used.

NOTE: Capacitors must be X5R or X7R dielectric formulations.

NOTE: Please refer to product datasheet for specific recommendations.

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EN5337QI Evaluation Board Application Note

August 2008 V1.0

Contact Information

Enpirion, Inc.

685 Route 202/206

Suite 305

Bridgewater, NJ 08807

Phone: 908-575-7550

Fax: 908-575-0775

Enpirion reserves the right to make changes in circuit design and/or

specifications at any time without notice. Information furnished by Enpirion is

believed to be accurate and reliable. Enpirion assumes no responsibility for its

use or for infringement of patents or other third party rights, which may result

from its use. Enpirion products are not authorized for use in nuclear control

systems, as critical components in life support systems or equipment used in

hazardous environment without the express written authority from Enpirion.

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