Texas Instruments LMH9226RRL-EVM, Руководство пользователя, Страница: 3 / 16

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3 SBOU237 – December 2019
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LMH9226 Evaluation Module
a. Short terminals 1 and 2 on J5 to put the LMH9226 device in its power down state. The supply
current (I
Q
) 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 2.2-GHz to 3-GHz signal frequency for testing out the
LMH9226 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 LMH9226 device input is tuned to 50- Ω matching impedance in the 2.2-GHz to 3-GHz
frequency band of operation. To minimize signal reflections due to impedance mismatch, TI
recommends using approximately 3- to 6-dB attenuator pad 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 LMH9226 device output is internally matched to 50- Ω differential impedance, the
onboard discrete L and C components transform the differential output impedance to 100- Ω in the
2.2-GHz to 3-GHz frequency band. See Table 1 for the discrete L and C component values used
on the LMH9226 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 balun which operates in the same frequency band as the LMH9226
device to avoid any setup issues. Also, use of an approximate 3- to 6-dB attenuator pad is
recommended at the three terminals of the passive balun for 50-
Ω matching 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- Ω differential impedance in the 2.2-GHz to 3-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 LMH9226 EVM.