THS3215 Datasheet, PDF (22/71 Pages) Texas Instruments – THS3215 650-MHz, Differential to Single-Ended DAC Output Amplifier

THS3215
SBOS780A – MARCH 2016 – REVISED APRIL 2016
www.ti.com
8 Parameter Measurement Information
8.1 Overview
The THS3215 comprises three blocks of high-performance amplifiers. Each block requires both frequency-
response and step-response characterization. The midscale buffer and OPS use standard, single-ended I/O test
methods with network analyzers, pulse generators, and high-speed oscilloscopes. The differential to single-
ended input stage (D2S) requires a wideband differential source for test purposes. All ac characterization tests
were performed using the THS3215 evaluation module (EVM). The THS3215EVM offers many configuration
options. For most of the D2S-only tests, the OPS was disabled. Figure 67 shows a typical configuration for an ac
frequency-response test of the D2S.
The THS3215EVM includes unpopulated, optional, passive elements at the D2S inputs to implement a
differential filter. These elements were not used in the D2S characterization, and the two input pins were
terminated to ground through 49.9-Ω resistors. DC test points are provided through 10-kΩ or 20-kΩ resistors on
all THS3215 nodes. Figure 67 also shows the output network used to emulate a 200-Ω load resistance (R_LOAD)
while presenting a 50-Ω source back to the D2S output pin. The R3 (= 169 Ω) and R4 (= 73.2 Ω) resistors
combine with the 50-Ω network analyzer input impedance to present a 200-Ω load at VO1 (pin 6), The
impedance presented from the input of the network analyzer back to the D2S output (VO1, pin 6) is 50-Ω. The
16.5-dB insertion loss intrinsic to this dc-coupled impedance network is removed from the characterization
curves. VREF (pin 14) was connected to GND for all the tests.
TP_IN+
VREF
14
R5
J1
10 k
Vin+
R1
50
From LMH3401
EVM
50
R2
J2
Vin-
10 k
R6
100
+IN
50
2 x1
+
250
500
3 x1
±IN
TP_VO1
R7
10 k
J3
R3
169
6
D2S_OUT
50-
Measurement
System
VO1
73.2
50
R4
TP_IN-
Figure 67. D2S Input and Output Interface Showing 50-Ω Differential Input, and 200-Ω R_LOAD at VO1
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