LMH6611 Datasheet, PDF (26/42 Pages) Intersil Corporation – PowerWise® Single Supply 345 MHz Rail-to-Rail Output Amplifiers

LMH6611, LMH6612
SNOSB00K – NOVEMBER 2007 – REVISED OCTOBER 2013
www.ti.com
Figure 70. LMH6611 and ADC121S101 Layout
SINGLE-ENDED TO DIFFERENTIAL ADC DRIVER
The single-ended to differential ADC driver in Figure 68 utilizes an LMH6612 dual op amp to buffer a single-
ended source to drive an ADC with differential inputs. One of the op amps is configured as a unity gain buffer
that drives the inverting (IN−) input of the op amp U2 and non-inverting (IN+) input of the ADC121S625. U2
inverts the input signal and drives the inverting input of the ADC121S625. The ADC driver is configured for a
gain of +2 to reduce the noise without sacrificing THD performance. The common mode voltage of 2.5V is set up
at the non-inverting inputs of both op amps U1 and U2. This configuration produces differential ±2.5 V_PP output
signals, when the single-ended input signal of 0 to V_REF is AC coupled into the non-inverting terminal of the op
amp and each non-inverting terminal of the op amp is biased at the mid-scale of 2.5V. The two output RC anti-
aliasing filters are used between both the outputs of U1 and U2 and the input of the ADC121S625 to minimize
the effect of undesired high frequency noise coming from the input source. Each RC filter has the cutoff
frequency of approximately 22 MHz.
V⁺
INPUT
10 PF
560:
560:
V⁺
0.1 PF 10 PF
-
LMH6612
+
U1
V⁺
560:
560:
33:
560:
560:
V⁺
0.1 PF 10 PF
-
LMH6612
+
U2
220 pF
V⁺
0.1 PF 10 PF
ADC121S625
33:
220 pF
Figure 71. Single-Ended to Differential ADC Driver
26
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: LMH6611 LMH6612