Texas Instruments LMH9235 User manual

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LMH9235 Evaluation Module
User's Guide
SBOU242–May 2020
LMH9235 Evaluation Module
This document outlines the basic steps and functions that are required to ensure the proper operation and
quick setup of the LMH9235RRL-EVM. This document also includes a schematic diagram, a bill of
materials (BOM), printed-circuit board (PCB) layouts, and test block diagrams. Throughout this document,
the abbreviations EVM, LMH9235 EVM and the term evaluation module are synonymous with the
LMH9235RRL-EVM, unless otherwise noted.
Contents
1 Description.................................................................................................................... 2
1.1 Features.............................................................................................................. 2
1.2 General Usage Information........................................................................................ 2
2 EVM Overview ............................................................................................................... 4
2.1 Schematic............................................................................................................ 4
2.2 PCB Layers.......................................................................................................... 5
2.3 LMH9235 EVM Bill of Material.................................................................................... 7
2.4 Stack up and Material.............................................................................................. 8
3 Test Setup Diagrams........................................................................................................ 8
3.1 S-Parameter Test Setup........................................................................................... 8
3.2 Noise Figure Test Setup........................................................................................... 9
3.3 Two-Tone OIP3 Test Setup...................................................................................... 10
List of Figures
1 Single Tone Setup for Gain and Output P1dB........................................................................... 2
2 LMH9235 EVM Schematic ................................................................................................. 4
3 Top Layer..................................................................................................................... 5
4 Layer 2 ........................................................................................................................ 5
5 Layer 3 ........................................................................................................................ 6
6 Bottom Layer................................................................................................................. 6
7 LMH9235 EVM Stack-up (Units in Mils) .................................................................................. 8
8 S-Parameter Test Setup.................................................................................................... 8
9 Input PCB Trace Loss vs Frequency...................................................................................... 9
10 Output PCB Trace Loss vs Frequency ................................................................................... 9
11 Noise Figure Test Setup.................................................................................................... 9
12 OIP3 Test Setup............................................................................................................ 10
List of Tables
1 LMH9235 EVM BOM........................................................................................................ 7
Trademarks
Isola is a registered trademark of Isola USA Corporation.
All other trademarks are the property of their respective owners.

(J3)
LMH9235
+3.3-V Single Bench
Power Supply
+3.3 V
GND
(J2)
LMH9235RRLEVM
(J1)
(J5)
DMM
(Measure Current)
123
Jumper
1.8 V
(J4)
RF Signal Generator
Spectrum Analyzer
Marki BAL-0010
or similar
0°
180°
2:1, Zo = 50 Ÿ
Zo(diff) = 100 Ÿ
3-dB pad
3-dB pad
3-dB pad
3-dB pad
FLFHGHz
Frequency Support:
FL±FH= 3.3±3.8 GHz
Zi(se) = 50 Ÿ Zo(diff) = 50 Ÿ
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LMH9235 Evaluation Module
1 Description
The LMH9235 evaluation module (EVM) is used to evaluate the LMH9235 device, which is a single-ended
input to differential output RF gain block amplifier available in a 2 × 2-mm2, 12-pin RRL package. The
device is well-suited to support requirements for the next generation 5G m-MIMO active antenna system
while interfacing with the input of transceiver. The EVM is designed to quickly demonstrate the
functionality and performance of the LMH9235 device in the 3.3-GHz to 3.8-GHz receive frequency band
with 700 MHz of 1-dB bandwidth.
By default, the board is set up for 50-Ωsingle-ended input matching and 100-Ωdifferential output
matching for easy interface with 50-Ωtest equipment. The EVM is ready to connect to a +3.3-V power
supply, signal source, and test instruments through the use of onboard connectors.
1.1 Features
• Operates on a single +3.3-V supply.
• Designed for a single-ended 50-Ωinput matching and 100-Ωdifferential output matching interface.
• Simple interface to the inputs and output through onboard SMA connectors.
• Power down option available onboard using a jumper connector.
Figure 1. Single Tone Setup for Gain and Output P1dB
1.2 General Usage Information
This section provides general usage information for the LMH9235 EVM. See Figure 1 for a general single
tone setup diagram as a reference point for the following instructions. Some components such as supply
bypass capacitors and power down reference voltage generation circuits are omitted in Figure 1 for clarity.
1. Recommended power up sequence:
a. Before connecting the power-supply cables to the EVM, set the DC output power supply to +3.3 V.
b. Set the current limit of the DC output power supply at 150 mA.
c. Making sure the supply is turned off, connect the power supply cables to the J1 connector of the
EVM.
d. Now turn on the DC power supply of VCC = +3.3 V. The supply current (IQ) drawn from the power
supply should be approximately 80 mA.
e. If the supply current is low, ensure that the device is not disabled by shorting the jumper
connection for J5 between 2 and 3 header pins.
2. Power-down option:

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LMH9235 Evaluation Module
a. Short terminals 1 and 2 on J5 to put the LMH9235 device in its power down state. The supply
current (IQ) drawn should be < 15 mA.
3. Single tone measurement setup recommendation:
a. Connect an RF signal generator to input J3 SMA connector.
b. The RF signal generator used must support 3.3-GHz to 3.8-GHz signal frequency for testing out
the LMH9235 EVM.
c. When measuring the EVM for single tone distortion products, TI recommends using an RF band
pass filter (not shown in Figure 1) between the signal source and J3 SMA input.
d. The LMH9235 device input is tuned to 50-Ωmatching impedance in the 3.3-GHz to 3.8-GHz
frequency band of operation. To minimize signal reflections due to impedance mismatch, TI
recommends using an attenuator pad of approximately 3-dB to 6-dB between the source and J3
SMA input.
e. The EVM outputs are fully differential (or 180° out-of-phase) at J2 and J4 SMA connectors.
Although the LMH9235 device output is internally matched to 50-Ωdifferential impedance, the
onboard discrete L and C components transform the differential output impedance to 100-Ωin the
3.3-GHz to 3.8-GHz frequency band. See Table 1 for the discrete L and C component values used
on the LMH9235 EVM.
f. When connecting to a spectrum analyzer single-ended input, the differential signal out of the EVM
should be converted to a single-ended signal using a passive balun as shown in Figure 1.
g. It is recommended to use a balun which operates in the same frequency band as the LMH9235
device to avoid any setup issues. Also, using an attenuator pad of approximately 3-dB to 6-dB is
recommended at the three terminals of the passive balun for 50-Ωmatching between the EVM
output and spectrum analyzer input.
h. Lastly, it is recommended to properly characterize and account for the insertion loss of RF coaxial
(coax) cables, attenuator pads, and passive baluns to measure accurate gain and power levels for
the device.
4. Matching or tuning options:
a. Solder mask has been removed along the RF signal paths and VCC path allowing an easy method
to slide surface mount components along these traces for optimal tuning.
b. The device differential output is tuned for 100-Ωdifferential impedance in the 3.3-GHz to 3.8-GHz
frequency band using discrete L and C components. The trace impedance is calculated by the
stack-up configuration as given in Section 2.4. See Table 1 for the L and C component values
used on the LMH9235 EVM.

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LMH9235 Evaluation Module
2 EVM Overview
This section includes the schematic diagram, a bill of materials (BOM), PCB layer prints, and EVM stack-
up information.
2.1 Schematic
Figure 2 shows the LMH9235 EVM schematic.
Figure 2. LMH9235 EVM Schematic

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2.2 PCB Layers
Figure 3 through Figure 6 illustrate the PCB layers for this EVM.
Figure 3. Top Layer
Figure 4. Layer 2

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Figure 5. Layer 3
Figure 6. Bottom Layer

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LMH9235 Evaluation Module
2.3 LMH9235 EVM Bill of Material
Table 1. LMH9235 EVM BOM
Common BOM
Item
#Designator Quantity Value Description Footprint Manufacturer Part Number
1 !PCB1 1 Printed Circuit Board Any AMPS094
2 C1 1 1 µF CAP, CERM, 1 µF, 10 V, ±20%,
X5R, 0201 0201 Samsung Electro- Mechanics CL03A105MP3NSNC
3 C2 1 0.01 µF CAP, CERM, 0.01 µF, 10 V, ±10%,
X7R, 0201 0201 MuRata GRM033R71A103KA01D
4 C3 1 0.1 µF CAP, CERM, 0.1 µF, 16 V, ±10%,
X5R, 0201 0201_033 MuRata GRM033C71C104KE14D
5 C5 1 22 pF CAP, CERM, 22 pF, 6.3 V, ±2%,
C0G/NP0, 0201 0201_033 MuRata GJM0335C0J220GB01D
6 J1 1 Terminal Block, 5.08 mm, 2×1, TH PhoenixContact_17157
21 Phoenix Contact 1715721
7 J2, J3, J4 3 SMA JACK 50 Ω, R/A, SMT Rosenberger_32K243-
40ML5 Rosenberger 32K243-40ML5
8 J5 1 Header, 100 mil, 3x1, Tin, TH CONN_PEC03SAAN Sullins Connector
Solutions PEC03SAAN
9 R1 1 2.49 kΩRES, 2.49 k, 1%, 0.063 W, AEC-
Q200 Grade 0, 0402 0402 Vishay-Dale CRCW04022K49FKED
10 R2 1 3.24 kΩRES, 3.24 k, 1%, 0.063 W, AEC-
Q200 Grade 0, 0402 0402 Vishay-Dale CRCW04023K24FKED
11 SH-J1 1 1×2 Shunt, 100 mil, Gold plated, Black SNT-100-BK-G Samtec SNT-100-BK-G
12 FID1, FID2,
FID3 0Fiducial mark. There is nothing to buy or mount. Fiducial10-20 N/A N/A
13 C4, C6 2 1.5 pF CAP, Film, 1.5 pF, 50 V, 0201
SMD 0201 AVX 02015J1R5PBSTR
14 L2 1 4.3 nH Inductor RF Chip Thin Film 4.3nH 3% 500 MHz 14Q-Factor 350 mA
400 mΩDCR 0201 Paper T/R 0201 Murata LQP03TN4N3H02D
15 U1 1 LMH9235IRRL, RRL0012A
(WQFN-12) RRL0012A Texas Instruments LMH9235IRRL
16 L1 0

(J3)
LMH9235
(J2)
LMH9235RRLEVM
(J4)
Vector Network Analyzer
Zo(diff) = 100 Ÿ
Zi(se) = 50 Ÿ
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LMH9235 Evaluation Module
2.4 Stack up and Material
The LMH9235 EVM is a 56-mil, 4-layer board whose material type is Isola®370HR. The top layer routes
the power, ground, and signals to and from the device. The signal impedance is targeted at 49.9 Ω. The
bottom 3 layers are ground layers.
Figure 7. LMH9235 EVM Stack-up (Units in Mils)
3 Test Setup Diagrams
This section includes general recommendations for S-parameter, noise figure, and two-tone OIP3 setup
while measuring the LMH9235 EVM.
3.1 S-Parameter Test Setup
Figure 8. S-Parameter Test Setup
Use the following guidelines for S-parameter measurement:
1. S-parameter measurement is typically done using a Vector Network Analyzer (VNA), as Figure 8
shows. For measuring the LMH9235 EVM, a 4-port VNA is recommended which can generate and
receive truly differential signals at the input and output ports.
2. Before connecting the RF coax cables to the LMH9235 EVM, you must calibrate the VNA along with
the cables using a calibration kit. This accounts for any cable losses in the S-parameter calculation at
the VNA and helps set reference impedance at the cable ends.
3. Make sure the frequency sweep and output power level from the VNA is set within the linear operating
range of the LMH9235 devices. The resolution bandwidth (RBW) and dynamic range of the VNA can
be adjusted to give optimum sweep time for the measurement.
4. It is important to account for onboard trace losses at the input and output pins of the device. De-
embedding of the input and output traces is recommended to improve the S-parameter measurement

(J3)
LMH9235
(J2)
LMH9235RRLEVM
(J4)
ENR Diode
Spectrum Analyzer or
Noise Figure Analyzer
Marki BAL-0010
or Similar
0°
180
°
2:1, Zo = 50 Ÿ
Zo(diff) = 100 Ÿ
3-dB pad
3-dB pad
3-dB pad
3-dB pad
Zi(se) = 50 Ÿ
Frequency (MHz)
Trace Loss (dB)
3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
Frequency (MHz)
Trace Loss (dB)
3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000
-0.5
-0.4
-0.3
-0.2
-0.1
0
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LMH9235 Evaluation Module
that is representative of the device performance. Figure 9 and Figure 10 give typical input and output
trace losses measured on the LMH9235 EVM, respectively.
Figure 9. Input PCB Trace Loss vs Frequency
Figure 10. Output PCB Trace Loss vs Frequency
3.2 Noise Figure Test Setup
Figure 11. Noise Figure Test Setup
Use the following guidelines for Noise Figure (NF) measurement:
1. The traditional Y-factor method can be used for the NF measurement using a Noise Diode and a
spectrum analyzer (or a Noise Figure Analyzer), as Figure 11 shows.
2. While doing the measurement, take into account any RF cable losses to the EVM board. Any external
input attenuator added for matching will result in proportional NF degradation and must be calibrated
out in the measurement.
3. Also, onboard losses of the input traces at the device input pin must be factored into the NF
measurement.
4. If the device output loss is significant, it is important to factor the output loss into the NF measurement.
5. Using the Friis equation is helpful when calculating combined NF of the measurement setup, and then
back calculating the individual device noise figure.

(J3)
LMH9235
(J2)
LMH9235RRLEVM
(J4)
RF Signal Gen 1
Spectrum Analyzer
Marki BAL-0010
or Similar
0°
180
°
2:1, Zo = 50 Ÿ
Zo(diff) = 100 Ÿ
3-dB pad
3-dB pad
3-dB pad
3-dB pad
Zi(se) = 50 Ÿ
RF Signal Gen 2
Power Splitter/
Combiner
6-dB pad 6-dB pad
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3.3 Two-Tone OIP3 Test Setup
Figure 12. OIP3 Test Setup
Use the following guidelines for two-tone OIP3 measurement:
1. As Figure 12 shows, combine two signal generator outputs using an in-phase power splitter and
combiner. A 6-dB attenuator is recommended at the signal generator outputs to prevent the generators
from talking to each other and resulting in signal generator IMD3 spurs.
2. Set both the signal generator outputs to a power level and frequency spacing such that it would yield
the desired output power (POUT) at the device.
3. TI recommends that the output power level is within the linear operation range of the LMH9235 device.
For example, if the total desired output power at the device is 8 dBm, then set the signal generators
such that each of the fundamental output power results in 2 dBm per tone. However, if each output
tone is at 8 dBm instead, the amplifier linearity will degrade as a result of higher total composite output
power of 14 dBm at the device outputs. As a general rule, it is recommended to keep the total output
power level approximately 6 to 8 dB lower than the 1-dB compression point. Also, see the device data
sheet for the recommended output power levels supported by the device.
4. For the OIP3 test, the two tones can be spaced ±10 MHz with respect to the desired center frequency.
5. TI recommends setting the spectrum analyzer attenuation setting from 20 to 26 dB based on sweet
spot of the incoming input power level.
6. Keep spectrum analyzer RBW and VBW settings identical for main tone and IM3 products.
7. For output IP3 calculation, take into account combined losses at the desired frequency band between
the LMH9235 device output to the spectrum analyzer input. The combined power losses include loss
due to PCB output trace, RF coax cable, 0/180◦passive balun and any attenuator pad used for external
matching purposes. The calculated OIP3 is given in .
Output IP3 = (PIN_SA – IMD3) / 2 + PIN_SA + PLOSS
where,
• PIN_SA = Input power per tone into the spectrum analyzer
• PLOSS = Power loss from the device output to the spectrum analyzer input
• IMD3 = Higher power of the two inter-modulation distortion products recorded at either 2f1 – f2 or 2f2 – f1
8. The thing to note in is the PIN_SA + PLOSS = POUT which is the amplifier output power per tone.