Texas Instruments LM3248 User manual

Using the LM3248 Evaluation Module
User's Guide
Literature Number: SNAA196
September 2013
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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
10 F
1 F Low ESL
VBATT
2.7V to 5.5V
FB
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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www.ti.com 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
3
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LM3248 Evaluation Module Photo www.ti.com
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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www.ti.com 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.
5
SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module
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Turn-off Sequencing www.ti.com
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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www.ti.com 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
7
SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module
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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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www.ti.com LM3248 Evaluation Board Layout
Figure 9. Stackup
9
SNAA196–September 2013 LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module
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0306
1µF
C2
10µF
0402
C8 2.2µF
C11
DNI
1.6x2mm
1.5µHL3
3.2x1.0x2.5mm
1µHL1
PGND
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
C4
PGND
C5
SGND_BUCK
C3
ATB1
E1
ENABLE
D1 DGND E3 SGND_BOOST B2
PVIN_BOOST
A2 PVIN_BOOST
A3
VDD_BOOST
A1
VCON
D2
N/C
D3
ATB2
F1
PGND
F3
U1
LM3248
VBATT
GND
GND_BUCK
BOOST_OUT GND_BST
GND
GND
GND
ATB0
ENABLE
ATB1
ATB2
ATB2
470µF
C6
4.7µF
0402
C10
GND
GND
SW_BUCK
FB_BUCK
VOUT
VBATT
SW_BOOST
BG
MODE
ENABLE
ATB0
ATB1
GND
GND
0201
0.22µF
C14
PGND
GND
0603
0
R5
1
2 3 4 5
VOUT
0603
0
R1
100pF
0201
C3
1000pF
0201
C9
0402
10µF
C1
10µF
0402
C7
1 2
DNI FB1
DNI
1000pF
0201
C34
GND
0201
0.01µF
C20
GND
GND
GND
GNDGND
GNDGND
GND
GND
GND
GND
GND
GNDGND
GND
BG
MODE 499
0201
R6
499
0201
R7
499
0201
R3
01005
3300pF
C16
GND
1µF
0201
C18
01005
3300pF
C19
2.2µF
0402
C21
DNI
4.7µF
0402
C17
DNI
0
DNI
0402
R2
1
2
OUT_BST
1 2
LBST
1 2
ACB
1
2
VCON_S
1 2
LBUCK
470µF
C5
BUCK_OUT
1 2
BST_OUT
1
2
SW BST
1
2
PVIN BST
1
2
ATB0
1
2
SW BUCK
1
2
BKOUT
1
2
BG
1
2
MODE
1
2
VCON
1
2
EN
1
2
ATB2 1 2
ATB1
(Default:
Cuttable
short circuit)
(Default: Cuttable short circuit)
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15
17
19
16
18
20
P1
5103309-5
1 2
FB2
DNI
499
0201
R4
LM3248 Evaluation Module Schematic www.ti.com
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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