TRF37A32_15 Datasheet, PDF (23/36 Pages) Texas Instruments – TRF37x32 Dual Down Converter Mixer With Integrated IF AMP

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TRF37A32, TRF37B32, TRF37C32
SLASE37A – MAY 2014 – REVISED DECEMBER 2014
8.3 Feature Description
8.3.1 Low Power Mode
Low power mode is enabled by setting the active-high LPM terminal to a logic high. The device contains an
internal pull-down to engage normal operation when the terminal is left unconnected or floating.
Low power mode reduces the bias current in the LO amplifier portion of the device and affects both channels.
Total current consumption is reduced 30% while lowering analog performance metrics.
8.3.2 Power Down
Each channel is powered down individually through the active-high PDA and PDB terminals. A logic high sets the
respective channel in power down. The device contains an internal pull-down to engage normal operation when
the terminal is left unconnected or floating.
Power down is implemented by removing bias in the IF amplifier. Operation of the opposite channel is not
affected when either channel is turned off. Turn-on and turn-off time is fast enough to serve in most TDD
applications.
1.2
1
0.8
0.6
Turn-Off
Turn-On
0.4
0.2
0
0
50
100
150
200
250
Time (nsec)
D001
Figure 74. Device power down turn-on and turn-off time
8.3.3 Single Ended RF Input
Each RF input is single-ended with a wideband internal balun to convert the input to a differential signal, as
shown in Figure 73. The center tap of the balun is internally grounded and is not available external to the device.
The RF input should be ac coupled to driving circuitry according to the chart in Table 1.
Table 1. RF Input AC coupling capacitor
Device
TRF37A32
TRF37B32
TRF37C32
Blocking Cap Value
20 pF
10 pF
10 pF
8.3.4 Single Ended LO Input
The LO input is single ended with an internal balun to convert the input to a differential signal. The LO drive path
includes a high frequency dual-mode oscillation inhibitor circuitry to ensure stable operation. For best operation it
is recommended to keep the LO drive level at 0 dBm or higher to ensure inhibitor circuit does not falsely engage.
At lower LO drive level, keep the LO power engaged to the device at power-up. At lower drive level the inhibitor
may engage within certain frequency bands when the LO power transitions.
At the extreme RF frequencies the LO input bandwidth will force operation to either high side injection (HSI) or
low side injection (LSI). Table 2 provides the operating range of the LO for each device.
Table 2. LO Input Frequency Operating Range
Device
TRF37A32
TRF37B32
Operating Range
600 - 1400 MHz
500 - 2900 MHz
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Product Folder Links: TRF37A32 TRF37B32 TRF37C32