LMH6517 Datasheet, PDF (15/34 Pages) National Semiconductor (TI) – Multi Standard, IF and Baseband, Dual, DVGA

LMH6517
www.ti.com
SNOSB19K – NOVEMBER 2008 – REVISED MARCH 2013
APPLICATION INFORMATION
The LMH6517 is a fully differential amplifier optimized for signal path applications up to 400 MHz. The LMH6517
has a 200Ω input and a low impedance output. The gain is digitally controlled over a 31.5 dB range from +22dB
to −9.5dB. The LMH6517 is optimized for accurate gain steps and minimal phase shift combined with low
distortion products. This makes the LMH6517 ideal for voltage amplification and an ideal ADC driver where high
linearity is necessary. The LMH6517 was designed for differential signal inputs only. Single ended inputs require
a balun or transformer as shown on the evaluation board.
V_CC
RF
200 ½ LMH6517
ADC
LO
6
GAIN 0-5
LATCH
Figure 40. LMH6517 Typical Application
5
OUT +
4
3
COMMON MODE
= 2.5V
2
1.25 V_P
1
OUT -
0
0 45 90 135 180 225 270 315 360
PHASE (°)
Figure 41. Output Voltage with Respect to the Output Common Mode
In order to help with system design TI offers the SP16160CH1RB High IF Receiver reference design board. This
board combines the LMH6517 DVGA with the ADC16DV160 ADC and provides a ready made solution for many
IF receiver applications. The SP16160CH1RB delivers an IF chain receiver sensitivity of -105 dBm, with a 9 dB
carrier-to-noise ratio in a 200 kHz channel, at 192 MHz input IF. With the digitally-controlled variable gain
amplifier (DVGA) set at a maximum gain of 22 dB, the sensitivity is limited primarily by the noise contribution of
the DVGA. In the presence of a strong blocker, with the DVGA gain set at 12 dB and blocker level kept at 1.6
dBm input to the ADC, the SP16160CH1RB board delivers sensitivity of -86 dBm. In this blocking condition, the
receiver sensitivity is determined by the ADC’s high spurious-free dynamic range (SFDR).
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