Texas Instruments LM3248 Manuale utente

Using the LM3248 Evaluation Module

User's Guide

Literature Number: SNAA196

September 2013

All trademarks are the property of their respective owners.

Apps

Processor

VCC_PA

1.8V Logic

FB_

BUCK

BOOST BUCK

SW_

BUCK

PVIN_

BUCK

OUT_

BOOST

SW_

BOOST

SGND_

BOOST

BYPASS

CONTROL

ENABLE BOOST_

GATE MODE

PGND

PVIN_

BOOST

DGND

ACB

SGND_

BUCK

VDD_

BOOST

VDD1_

BUCK

VCON

VDD2_

BUCK

1.5 H

1.0 H10 F

10 F

1 F Low ESL

VBATT

2.7V to 5.5V

1 nF

ACB

BGND

User's Guide

SNAA196–September 2013

LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter

Evaluation Module

1 Introduction

The LM3248 evaluation module is a working demonstration of a PWM/PFM Boost-Buck DC/DC converter

designed to provide efficient utilization of battery power for 2G/3G/4G and 3GPP/LTE RF subsystems.

The LM3248 incorporates a step-up (Boost) and a variable output step-down (Buck) DC-DC converter.

The Boost converter provides the RF power subsystem the capability to operate at lower battery voltages

as well as increased PA linearity and transmit power margins over a wider battery voltage supply range.

This application note contains information specific to the evaluation board. For device details and electrical

characteristics, please refer to the LM3248 data sheet. If you are considering using the LM3248 in a

system design, please see the "PCB Layout Considerations" section of the device data sheet.

2 Operating Conditions

The device will operate under the following conditions:

• VIN range: 2.7V to 5.5V

• VOUT Range: 0.4V to 4.0V

• IOUT range: 0A to 2.5A

3 Package

The LM3248 is available in a 30-bump (0.4 mm pitch) lead-free DSBGA package.

4 Typical LM3248 Boost-Buck Application Diagram

2LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module SNAA196–September 2013

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LM3248 Bill of Materials

5 LM3248 Bill of Materials

Designator Qty. Description Manufacturer Mfr Part Number Supplier 1 Supplier 2

BOOST_OUT, Standard Banana Jack,

3 Keystone 6091 Digi-Key

BUCK_OUT, VBATT Insulated, Red

CAP, CERM, 10µF, 6.3V,

C1, C7, C8 3 Samsung CL05A106MQ5NUNC Digi-Key

±20%, X5R, 0402

CAP, CERM, 4.7µF, 10V,

C10 1 MuRata GRM155R61A475M See Mfr.

±20%, X5R, 0402

CAP, CERM, 0.22µF, 6.3V,

C14 1 TDK C0603X5R0J224M Digi-Key Mouser

±20%, X5R, 0201

CAP, CERM, 3300pF,

C16, C19 2 TDK C0402X5R0J332K020BC Digi-Key

6.3V, ±10%, X5R, 01005

CAP, CERM, 1µF, 10V,

C18 1 Samsung CL03A105MP3NSNC Digi-Key

±20%, X5R, 0201

CAP, CERM, 1µF, 10V,

C2 1 Taiyo Yuden LWK107BJ105MV See Mfr.

±20%, X5R, 0306

CAP, CERM, 0.01µF, 6.3V,

C20 1 TDK C0603X5R0J103K Digi-Key Mouser

±10%, X5R, 0201

CAP, CERM, 100pF, 25V,

C3 1 MuRata GRM033R71E102KA01D Digi-Key Arrow

±10%, X5R, 0201

CAP, TANT, 470µF, 10V,

C5, C6 2 ±10%, 0.04Ω, 7260-38 Kemet T495E477K010ATE040 Digi-Key

SMD

CAP, CERM, 1000pF, 25V,

C9, C34 2 MuRata GMR022R71E102KA01D Digi-Key Farnell

±10%, X7R, 0201

GND, GND_BST, Standard Banaka Jack,

3 Keystone 6092 Digi-Key

GND_BUCK Insulated, Black

Machine Screw, Roun, #4- B&F Fastener

H1, H2, H3, H4 4 40 x 1/4, Nylon, Philips NY PMS 440 0025 PH Digi-Key

Supply

panhead

Standoff, Hex, 0.5"L #4-40

H5, H6, H7, H8 4 Keystone 1902C Digi-Key

x 1/4, Nylon

Inductor, Shielded, Metal

L1 1 Composite, 1µH, 2.6A, Toko 1276AS-H-1R0N See Mfr.

0.062Ω, 3225

Inductor, Shielded, Metal

L3 1 Composite, 1.5µH, 1.6A, Toko 1285AS-H-1R5M See Mfr.

0.144Ω, 2016

Header (shrouded) 100 mil, TE

P1 1 5103309-5 Digi-Key Mouser

10x2, TH Connectivity

R1, R5 2 RES 0Ω, 5%, 0.1W, 0603 Vishay-Dale CRCW06030000Z0EA Digi-Key Farnell

RES, 499Ω, 1%, 0.05W,

R3, R4, R6, R7 4 Vishay-Dale CRCW0201499RFKED Digi-Key Mouser

0201

LM3248 Boost-Buck DC- Texas

U1 1 LM3248TME T.I.

DC Converter Instrument

Emerson

Connector, RF Co-ax, 50Ω,

VOUT 1 Network 135-3701-201 Digi-Key Mouser

6GHz, Vertical, TH Power

ACB, ATB0, ATB1,

ATB2, BG, BK UT,

BST_OUT, EN, lBST, L Header, TH, 100mil, 2x1,

BUCK, MOD, 17 Gold-plated, 230mil above Samtec, Inc. TSW-102-07-G-S Digi-Key

OUT_BST, PVIN BST, insulator

SW BST, SW BUCK,

VCON, VCON_S CAP, CERM, 2.2µF, 6.3V

C11 1 MuRata DNI Digi-Key Mouser

±20%, X5R, 0402

CAP, CERM, 4.7µF, 10V

C17 1 MuRata DNI Digi-Key

±20%, X5R, 0402

SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module

LM3248 Evaluation Module Photo

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CAP, CERM, 2.2µF, 6.3V

C21 1 MuRata DNI Digi-Key

±20%, X5R, 0402

RES, 0Ω, 5%, 0.063W,

R2 1 Dale DNI Digi-Key

0402

(Not installed) 3.5A Ferrite

FB1, FB2 2 Bead, 60Ω@ 100MHz, TDK MPZ1608S600A Digi-Key Mouser

SMD

6 LM3248 Evaluation Module Photo

Figure 1. LM3248 Evaluation Board

4LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module SNAA196–September 2013

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Connecting to the LM3248 Evaluation Module

7 Connecting to the LM3248 Evaluation Module

NOTE: All of the control signals (BOOST_GATE (“BG”), MODE, ENABLE (“EN”) and VCON) can be

accessed on the bank of test access points just above connector P1, as shown in Figure 1.

The pins next to each of the silkscreened signal names are all grounded, with the exception

of the one labeled “VCON_S.” The pins with silkscreened dots indicate the active signal pins.

1. LM3248 EVM Jumper Settings

• The LBST, L BUCK & ACB 0.1” center slide-on jumpers located on the back side of the LM3248

Evaluation Board must be installed for proper operation. See Figure 8 for locations on back side of

EVM.

• The OUT_BST shunt on the top side of the LM3248 Evaluation Board adjacent to the

BOOST_OUT banana jack is not required for normal operation, but must be in place if this banana

jack is used for monitoring the Boost Output voltage.

2. Connect the EN pin signal source with the signal source set to 0V.

3. Connect the VBATT supply to the red (+) and black (ground) banana connector pins on the left side of

the module.

4. Connect the other control signals (BOOST_GATE, MODE, and VCON) to the evaluation module,

making sure the signal sources are first set to 0V.

NOTE: BOOST_GATE is a logic level signal (see the LM3248 data sheet) which represents the TTI

frame interval. A pulse or function generator should be used to drive this pin, but should be

configured to drive a high impedance load so that the level seen on the instrument panel is

the same as that measured into a high-Z load (50Ωmode will put out 2X the indicated

voltage when driving a high-Z load). Set the period to 2G=4.616 ms, 3G=10 ms or 4G=1 ms,

and the pulse width to 45 µs, to emulate the corresponding intervals that the boost "bias"

circuits need to run in these respective modes.

5. Connect the load (resistor, electronic load , or PA module) to the BUCK_OUT red (+) and GND_BUCK

black (ground) banana jacks.

8 Turn-on Sequencing

1. After insuring that ENABLE, BOOST_GATE and MODE pins are all at 0V, turn VBATT ON, and then

turn ON the ENABLE, BOOST_GATE and MODE signals (MODE=LOW for 3G/4G, HIGH for 2G). For

best accuracy, measure VBATT across the "PVIN BST" test points on the bottom of the EVM.

2. Turn on and adjust VCON to obtain the desired BUCK OUT voltage level (VCON = VOUT/2.5), which,

for best accuracy, is measured across the "BK OUT" test points on the bottom side of the EVM.

SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module

Turn-off Sequencing

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9 Turn-off Sequencing

1. Switch ENABLE, BOOST_GATE and VCON to 0V.

2. Turn off VBATT supply.

10 Bottom Layer Test and Jumper Pairs

The signals below may be monitored by attaching scope probes or clip leads to the corresponding pins.

The dotted pin is the signal. The adjacent (undotted) is the ground pin.

Test Points:

• PVIN BST - Boost input node (VBATT connection)

• SW BST - Boost switch node

• BST_OUT - Boost output node

• SW BUCK - Buck switch node

• BK OUT - Buck output note

Jumpers (see Figure 8 for locations):

• LBST - Boost inductor jumper

• L BUCK - Buck inductor jumper

• ACB - ACB jumper

6LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module SNAA196–September 2013

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LM3248 Evaluation Board Layout

11 LM3248 Evaluation Board Layout

Figure 2. Top Layer Figure 3. Bottom Layer

Figure 4. Mid Layer 1 Figure 5. Mid Layer 2

SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module

0.1 inch jumpers

are installed here

LM3248 Evaluation Board Layout

www.ti.com

Figure 6. Mid-Layer 3 Figure 7. Mid Layer 4

Figure 8. Bottom Layer (Mirrored)

8LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module SNAA196–September 2013

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LM3248 Evaluation Board Layout

Figure 9. Stackup

SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module

0306

1µF

10µF

0402

C8 2.2µF

C11

DNI

1.6x2mm

1.5µHL3

3.2x1.0x2.5mm

1µHL1

PGND

GND GND

PGND

4ampmax

PGND

SW_BOOST B3

VDD2_BUCK F2

FB_BUCK E2

ACB F4

PVIN_BUCK E4

OUT_BOOST A4

VDD1_BUCK C2

SW_BOOST B4

SW_BOOST B5

OUT_BOOST A5

PVIN_BUCK E5

ACB F5

SW_BUCK D4

SW_BUCK D5

BOOST_GATE B1

MODE C1

PGND

SGND_BUCK

ATB1

ENABLE

D1 DGND

E3 SGND_BOOST

PVIN_BOOST

A2 PVIN_BOOST

VDD_BOOST

VCON

N/C

ATB2

PGND

LM3248

VBATT

GND

GND_BUCK

BOOST_OUT GND_BST

GND

ATB0

ENABLE

ATB1

ATB2

470µF

4.7µF

0402

C10

GND

SW_BUCK

FB_BUCK

VOUT

VBATT

SW_BOOST

MODE

ENABLE

ATB0

ATB1

GND

0201

0.22µF

C14

PGND

GND

0603

VOUT

0603

100pF

0201

1000pF

0201

0402

10µF

0402

1 2

DNI FB1

DNI

1000pF

0201

C34

GND

0201

0.01µF

C20

GND

GNDGND

GND

GNDGND

GND

MODE 499

0201

499

0201

499

0201

01005

3300pF

C16

GND

1µF

0201

C18

01005

3300pF

C19

2.2µF

0402

C21

DNI

4.7µF

0402

C17

DNI

0402

OUT_BST

LBST

ACB

VCON_S

LBUCK

470µF

BUCK_OUT

BST_OUT

SW BST

PVIN BST

ATB0

SW BUCK

BKOUT

MODE

VCON

ATB2 1

ATB1

(Default:

Cuttable

short circuit)

(Default: Cuttable short circuit)

1 2

3 4

5 6

7 8

9 10

11 12

13 14

5103309-5

1 2

FB2

DNI

499

0201

LM3248 Evaluation Module Schematic

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12 LM3248 Evaluation Module Schematic

10 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module SNAA196–September 2013

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