LMH2832 Datasheet, PDF (19/46 Pages) Texas Instruments – LMH2832 Fully Differential, Dual, 1.1-GHz, Digital Variable-Gain Amplifier

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9 Detailed Description
LMH2832
SBOS709A – JULY 2016 – REVISED JULY 2016
9.1 Overview
Each channel of the LMH2832 consists of an input attenuator block followed by a fully differential amplifier that
has a gain of 30 dB. The attenuator has a range of 0 dB to –39 dB in 1-dB steps that is controlled by an SPI
interface. The two channels can be controlled independently using the digital interface including power-down and
bias settings. A separate analog power-down pin (PDA, PDB) is also included for each channel so that the
device can bet set to a low-power state without waiting for a serial write to a register. The internal registers also
include a power-on-reset (POR) that ensures the device starts in a known state after the power is reset.
9.2 Functional Block Diagram
INPA
150
INMA
PDA
CS
SCLK
SDI
SDO
PDB
INMB
150
INPB
1-dB Attenuator Steps:
0 dB to -39 dB
FDA
G = 30 dB
SPI
POR
Channel A Control Logic
Channel B Control Logic
1-dB Attenuator Steps:
0 dB to -39 dB
FDA
G = 30 dB
OUTPA
OUTMA
OUTMB
OUTPB
9.3 Feature Description
9.3.1 Analog Input Characteristics
The LMH2832 is a dual-channel device with two identical channels (A and B) that each have differential input
pins (INP and INM) that denote the positive and negative inputs, respectively. The inputs are expected to be ac-
coupled only, typically through a transformer or capacitor. The amplifier self-biases the input common-mode to
mid-supply for the maximum input voltage range. The inputs of the LMH2832 can only be driven differentially. For
single-ended input source applications, use a balun or fully differential amplifier (such as the LMH3401 or
LMH5401) that can convert single-ended to differential signals before the LMH2832.
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