LMH2832 Datasheet, PDF (18/46 Pages) Texas Instruments – LMH2832 Fully Differential, Dual, 1.1-GHz, Digital Variable-Gain Amplifier

LMH2832
SBOS709A – JULY 2016 – REVISED JULY 2016
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8.6 Pulse Response, Slew Rate, and Overdrive Recovery
For time-domain measurements, the standard EVM is driven through an impedance transformation pad and a
balun again to convert a single-ended output from the test equipment to the differential inputs of the LMH2832.
The differential outputs are directly connected to the oscilloscope inputs, with the differential signal response
calculated using trace math from the two separate oscilloscope inputs.
8.7 Power-Down
The standard EVM is used for this test by completely removing the shorting block on jumper JPD. A high-speed,
50-Ω pulse generator is used to drive the PDx pin that toggles the output signal on or off depending upon the
PDx pin voltage.
8.8 Crosstalk, Gain Matching, and Phase Matching
The standard EVM is used for these tests with both channels enabled. For gain and phase matching, the
responses of both channels are measured on a network analyzer and the gain and phase values are compared.
For crosstalk, a single channel is driven with a signal on the network analyzer when the other channel is
measured.
8.9 Output Measurement Reference Points
The LMH2832 has two on-chip, 10-Ω output resistors on each channel. When matching the output to a 100-Ω
load, the evaluation module (EVM) uses an external 40-Ω resistor on each output leg to complete the output
matching. The inclusion of on-chip output resistors creates two potential reference points for measuring the
output voltage. The first reference point is at the internal amplifier output (OUT_AMP), and the second reference
point is at the externally-matched 100-Ω load (OUT_LOAD). The measurements in the Electrical Characteristics
table and in the Typical Characteristics section are referred to the (OUT_AMP) reference point unless otherwise
specified. The conversion between reference points is a straightforward correction of 3 dB for power and 6 dB for
voltage, as shown in Equation 1 and Equation 2. The measurements are referenced to OUT_AMP when not
specified.
VOUT_LOAD = (VOUT_AMP – 6 dB)
(1)
POUT_LOAD = (POUT_AMP – 3 dB)
(2)
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