Texas Instruments Evaluation Board for the LMV834 3.3MHz EMI Hardened Operation Amplifier. LMV834MTEVAL LMV834MTEVAL 데이터 시트
제품 코드
LMV834MTEVAL
Layout Considerations
5
Layout Considerations
The layout of the evaluation board requires some attention. For decoupling the supply lines, it is
suggested that 10 nF capacitors be placed as close as possible to the op amp. For single supply, place a
capacitor between V
suggested that 10 nF capacitors be placed as close as possible to the op amp. For single supply, place a
capacitor between V
+
and V
−
. For dual supplies, place one capacitor between V
+
and the board ground,
and a second capacitor between ground and V
−
. On the LMV831 evaluation board, the decoupling of the
negative pin V
−
is implemented by a capacitor between V
+
and V
−
. This is done for easy routing and to
keep connections to the pins short. Even with the LMV831/LMV832/LMV834's inherent hardening against
EMI, it is still recommended to keep the input traces short and as far as possible from RF sources. Then
the RF signals entering the chip are as low as possible, and the remaining EMI can be, almost, completely
eliminated in the chip by the EMI reducing features of the LMV831/LMV832/LMV834.
EMI, it is still recommended to keep the input traces short and as far as possible from RF sources. Then
the RF signals entering the chip are as low as possible, and the remaining EMI can be, almost, completely
eliminated in the chip by the EMI reducing features of the LMV831/LMV832/LMV834.
6
Measurement Procedure
The measurement procedure is the same for all test circuits. To measure the input referred offset voltage
shift needed for calculating the EMIRR, the following procedure can be used:
shift needed for calculating the EMIRR, the following procedure can be used:
1. Measure V
OUT
when the RF signal is off.
2. Measure V
OUT
when the RF signal is on.
3. Translate measured V
OUT
voltages to input referred voltages. Translation is one-to-one in this case
since the gain is one in the IN+ test setup.
4. Subtract the two measured input referred voltages.
5. Verify if the offset shift is above the noise level of the op amp setup and the op amp is not saturated. If
this is not the case choose another RF level and start the procedure again.
6. Calculate the EMIRR.
7. If needed, transform the results to an EMIRR based on a 100 mV
P
RF signal.
7
Measurement Results
To show the sensitivity of the IN+ pin, two types of measurement results are presented using the LMV831
evaluation board:
evaluation board:
•
The EMIRR as a function of the frequency of the applied signal. The level of the signal is set to the
standard level of 100 mV
standard level of 100 mV
P
(
−
20 dBV
P
).
•
The EMIRR as a function of the level of the applied signal. The frequency is set to four typical values:
400 MHz, 900 MHz, 1.8 GHz, and 2.4 GHz.
400 MHz, 900 MHz, 1.8 GHz, and 2.4 GHz.
7.1
EMIRR Vs. Frequency
shows the EMIRR versus frequency for the various temperatures. The measurement is
performed with a fixed RF level of
−
20 dBV
P
and a varying RF signal frequency. The frequency range is
10 MHz to 10 GHz.
2
AN-1867 EMIRR Evaluation Boards for LMV831/LMV832/LMV834
SNOA530A – October 2008 – Revised April 2013
Copyright © 2008–2013, Texas Instruments Incorporated