C1608X7R1C473K [NSC]

Evaluation Board provides the design engineer with a fully functional; 评估板提供了设计工程师提供一个功能齐全


型号：	C1608X7R1C473K
厂家：	National Semiconductor
描述：	Evaluation Board provides the design engineer with a fully functional 评估板提供了设计工程师提供一个功能齐全
文件：	总10页 (文件大小：1211K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

National Semiconductor

Application Note 2066

Eric Lee

LM25119 Evaluation Board

September 28, 2010

ed to the J6 (OUT2+) and J5 (OUT2-/GND). Be sure to

choose the correct connector and wire size when attaching

the source power supply and the load.

Introduction

The LM25119EVAL evaluation board provides the design en-

gineer with a fully functional dual output buck converter, em-

ploying the LM25119 Dual Emulated Current Mode Syn-

chronous Buck Controller. The evaluation board is designed

to provide both 3.3V and 1.8V outputs over an input range of

6.0V to 36V. Also the evaluation board can be easily config-

ured for a single 3.3V, 16A regulator.

SOURCE POWER

The power supply and cabling must present low impedance

to the evaluation board. Insufficient cabling or a high

impedance power supply will droop during power supply ap-

plication with the evaluation board inrush current. If large

enough, this droop will cause a chattering condition during

power up. During power down, insufficient cabling or a high

impedance power supply will overshoot. This overshoot will

cause a non-monotonic decay on the output.

Performance of the Evaluation

Board

•

Input Voltage Range: 6.0V to 36V

Output Voltage: 3.3V (CH1), 1.8V (CH2)

Output Current: 8A (CH1), 8A (CH2)

Nominal Switching Frequency: 230 KHz

Synchronous Buck Operation: Yes

Diode Emulation Mode: Yes

An additional external bulk input capacitor may be required

unless the output voltage droop/overshoot of the source pow-

er is less than 0.5V. In this board design, UVLO setting is

conservative while UVLO hysteresis setting is aggressive.

Minimum input voltage can goes down with an aggressive

design. Minimum operating input voltage depends on the out-

put voltage droop/overshoot of the source power supply and

the forced off-time of the LM25119. Refer to the LM25119

datasheet for complete design information.

Hiccup Mode Overload Protection: Yes

External VCC Sourcing: No

Powering and Loading

Consideration

When applying power to the LM25119 evaluation board, cer-

tain precautions need to be followed. A misconnection can

damage the assembly.

When using an electronic load, it is strongly recommended to

power up the evaluation board at light load and then slowly

increase the load. If it is desired to power up the evaluation

board at maximum load, resistor banks must be used. In gen-

eral, electronic loads are best suited for monitoring steady

state waveforms.

PROPER BOARD CONNECTION

AIR FLOW

The input connections are made to the J1 (VIN) and J2 (RTN/

GND) connectors. The CH1 load is connected to the J3

(OUT1+) and J4 (OUT1-/GND) and the CH2 load is connect-

Prolonged operation with high input voltage at full power will

cause the MOSFETs to overheat. A fan with a minimum of

200LFM should be always provided.

30126101

FIGURE 1. Typical Evaluation Setup

301261

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QUICK START-UP PROCEDURE

LOAD TRANSIENT

STEP 1: Set the power supply current limit to at least 20A.

Connect the power supply to J1 and J2.

Figure 3 shows the transient response for a load of change

from 2A to 6A on 3.3V output. The upper waveform shows

output voltage droop and overshoot during the sudden

change in output current shown by the lower waveform.

STEP 2: Connect one load with an 8A capacity between J3

and J4. Connect another load with an 8A capacity between

J6 and J5.

STEP 3: Set input voltage to 12V and turn it on.

STEP 4: Measure the output voltages. CH1 should regulate

at 3.3V and CH2 should regulate at 1.8V.

STEP 5: Slowly increase the load current while monitoring the

output voltages. The outputs should remain in regulation up

to full load current.

STEP 6: Slowly sweep the input voltage from 6.0V to 36V

while monitoring the output voltages. The outputs should re-

main in regulation.

Waveforms

SOFT START

When applying power to the LM25119 evaluation board a

certain sequence of events occurs. Soft-start capacitors and

other components allow for a linear increase in output volt-

ages. The soft-start time of each output can be controlled

independently. Figure 2 shows the output voltage during a

typical start-up with a load of 0.5Ω on the 3.3V output, and

0.33Ω on the 1.8V output, respectively.

30126103

Conditions:

Input Voltage = 12VDC

Output Current 2A to 6A

Traces:

Top Trace: 3.3V Output Voltage, Volt/div = 100mV, AC coupled

Bottom Trace: Output Current Amp/Div = 2A

Horizontal Resolution = 0.5 ms/div

FIGURE 3. Load Transient Response

OVER LOAD PROTECTION

The evaluation board is configured with hiccup mode over-

load protection. The restart time can be programmed by C11.

Figure 4 shows hiccup mode operation in the event of an out-

put short on CH1 output. One channel may operate in the

normal mode while the other is in hiccup mode overload pro-

tection.

30126102

Conditions:

Input Voltage = 12VDC

0.5Ω Load on 3.3V output

0.33Ω Load on 1.8V output

Traces:

Top Trace: 3.3V Output Voltage, Volt/div = 1V

Bottom Trace: 1.8V Output Voltage, Volt/div = 1V

Horizontal Resolution = 1 ms/div

FIGURE 2. Start-up with Resistive Load

30126104

Conditions:

Input Voltage = 12VDC

Output Short on 3.3V

Traces:

Top Trace: SW voltage on CH1, Volt/div = 10V

Bottom Trace: Inductor Current Amp/div = 10A

Horizontal Resolution = 20 ms/div

FIGURE 4. Short Circuit

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EXTERNAL CLOCK SYNCHRONIZATION

Performance Characteristics

A TP1 (SYNC) test point has been provided on the evaluation

board in order to synchronize the internal oscillator to an ex-

ternal clock. Figure 5 shows the synchronized switching op-

eration. Each channel operates 180 degrees out of phase

from the other.

Figure 7 shows the efficiency curves. The efficiency of the

power converter is 90% at 12V with full load current. Monitor

the current into and out of the evaluation board. Monitor the

voltage directly at the input and output terminals of the eval-

uation board.

30126105

Conditions:

Input Voltage = 12VDC

8A on 3.3V output

8A on 1.8V output

Traces:

Top Trace: SYNC pulse, Volt/div = 5V

Middle Trace: SW voltage on CH1, Volt/div = 10V

Bottom Trace: SW voltage on CH2, Volt/div = 10V

Horizontal Resolution = 1 µs/div

30126107

FIGURE 7. Typical Efficiency vs Load Current

FIGURE 5. Clock Synchronization

SHUTDOWN

Figure 6 shows the shutdown procedure by powering off the

source power. When UVLO pin voltage is less than 1.26V, the

switching stops and soft-start capacitors are discharged by

internal switches.

30126106

Conditions:

Input Voltage = 12VDC

0.5Ω Load on 3.3v output

Traces:

Top Trace: Input Voltage, Volt/div = 10V

Middle Trace1: 3.3V Output, Volt/div = 2V

Middle Trace2: VCC, Volt/div = 5V

Bottom Trace: SS voltage, Volt/div = 5V

Horizontal Resolution = 20 ms/div

FIGURE 6. Shutdown

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EXTERNAL VCC SUPPLY & VCC DISABLE

Board Configuration

External VCC supply helps to reduce the temperature and the

power loss of the LM25119 at high input voltage. By populat-

ing D3 and D4, VCC can be supplied from an external power

supply. Use TP3 as an input of the external VCC supply with

0.1A current limit. R36, R35 and C45 should be populated

with proper value when the voltage of the external VCC is

smaller than 7V. The voltage at the VCCDIS pin can be mon-

itored at TP2. To prevent a reverse current flow from VCC to

VIN through the internal diode, the external VCC voltage

should always be lower than VIN.

INTERLEAVED BUCK OPERATION FOR SINGLE 3.3V

16A OUTPUT

The evaluation board is designed to be easily converted to a

3.3V, 16A single output regulator with the interleaved opera-

tion. Proper electronic load connection is shown in Figure 8.

Connecting the electronic load at the center of shorting bar is

recommended to prevent a voltage difference between CH1

and CH2 output. In order to produce a single 3.3V output with

16A maximum output current, populate R21 and R22 with

0Ω resistor and open R6, C15 and C14. The electronic load

should have over 16A capability to test the interleaved oper-

ation.

LOOP RESPONSE

TP5 and TP6 (TP7 and TP8) have been provided in order to

measure the loop transfer function of CH1 (CH2). Refer to

AN-1889 for detail information about the loop transfer function

measurement.

30126108

FIGURE 8. Load Connection for Single Output

30126109

FIGURE 9. Loop Response Measurement Setup

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Evaluation Board Schematic

30126110

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TABLE 1. Bill of Materials

Part

Value

Package

Part Number

Manufacturer

C1,C2,C3,C4,C5,C32,

C35,C36,C37,C38,C39

,C40,C41,C42

2.2 µF, 50V, X7R

1210

C3225X7R1H225K

TDK

C6,C7,C25,C29

C8,C10,C14,C16

1µF, 16V, X7R

100pF, 50V, C0G

0.47µF, 50V, X7R

0.47µF, 25V, X7R

0.047µF, 16V, X7R

6800pF, 25V, C0G

820pF, 50V, C0G

680µF, 6.3V

0603

0805

0603

Φ10

C1608X7R1C105K

C1608C0G1H101J

UMK212B7474KG

TDK

Taiyo Yuden

Murata

TDK

C11,C18,C19

C12,C13

GRM188R71E474KA12

C1608X7R1C473K

C1608C0G1E682J

C15,C17

TDK

C20,C21

C1608C0G1H821J

APXA6R3ARA681MJC0G

TDK

C22,C26

NIPPON CHEMI-

CON

C23,C24,C27,C28

22µF,10V, X7R

1000pF, 50V, X7R

1000pF,100V, C0G

1210

0603

0805

C1210C226K8RAC

C1608X7R1H102K

C2012C0G2A102J

Kemet

TDK

C30,C31

C33,C34

TDK

C43,C44,C45,C46,C47

3.9 ohm, 5%

52.3k, 1%

0805

0603

CRCW08053R90JNEA

MCR10EZHF5232

Vishay

Rohm

Vishay

15k, 1%

MCR03EZPFX1502

CRCW060322K1FKEA

22.1k, 1%

R5,R16,R21,R22,R35,

R36,R37

R6,R7

36.5k, 1%

0603

0805

CRCW060336K5FKEA

CRCW080510R0JNEA

Vishay

R8,R9,

R23,R24,R29,R30,

R31, R32

10 ohm, 5%

R10,R12

R11

6.98k, 1%

2.21k, 1%

5.49k, 1%

34k, 1%

0805

CRCW08056K98FKEA

MCR10EZHF2211

MCR10EZHF5491

CRCW060334K0FKEA

MCR03EZPJ000

Vishay

Rohm

R13

0805

Rohm

R14,R15

R17

0603

Vishay

0 ohm

0603

Rohm

R18,R20

R25,R26

R27,R28

D1,D2

0.008 ohm, 1W, 1%

5.1 ohm, 1W, 1%

0 ohm, 5%

60V, 1A

0815

RL3720WT-R008-F

ERJ-1TRQF5R1U

MCR10EZPJ000

Susumu

Panasonic-ECG

Rohm

2512

0805

SOD123F

PMEG6010CEH

NXP

D3,D4

L1,L2

6.8µH, 18.5A

40V, 58A

18.2x18.3

PowerPAK SO-8

LLP32

7443556680

SI7884BDP

LM25119

7693

Q1,Q2,Q3,Q4

Vishay

NSC

J1,J2,J3,J4,J5,J6

TP1,TP2,TP3

TP5,TP6,TP7,TP8

15A

Keystone

5002

Φ10

1040

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PCB Layout

30126111

30126115

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30126112

30126113

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30126114

30126116

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