Demonstration of Operation Over Common-Mode Voltage Range

2-3

EVM Setup and Operation

When using a general-purpose signal generator with 50-

Ω output impedance,

make sure that the signal levels are between 0 V and 5 V with respect to J18,

device under test ground (DUT GND), designated as GND2.

Apply the driver input signal (D) to connector J8. Resistor R14 provides

termination impedance matched to a standard 50-

Ω output- impedance signal

generator.

At the driver outputs, the EVM comes with a 100-

Ω resistor (R5) installed

across the differential outputs, as well as resistors R15 and R16, which add

another 102

Ω across the differential outputs. The parallel combination of R5

with R15 and R16 creates a total load of about 50

Ω at the driver outputs.

Figure 2 - 3. Configuration for Driver Evaluation

W11

R14

51

J8

Input Signal

TP4

W17

P3

U2

7

4

Jumper

6

1

3

2

W4

Driver

Enable

W3

Receiver

Enable

Jumper

Signal Source

With 50

Ω

Output

50

Ω Cable

R5

100

Ω

R18

51

Ω

R16

51

Ω

R16

51

Ω

R17

51

Ω

Driver

Output

The input/output characteristics of the driver can be observed by probing TP4

(driver input) and either P3 or W17 (driver output). In addition to the

single-ended outputs (with respect to GND2) and the differential outputs

available at P3 and W17, the common-mode output can be observed using

W11 as a test point.

2.2

Demonstration of Operation Over Common-Mode Voltage Range

A unique feature of the HVD2X family is the ability to operate with common-

mode voltages in the range from –20 V to 25 V. In order to demonstrate

SN65HVD22 operation over the extended range of common-mode voltage,

two EVMs are required. Figure 2 - 4 shows how two EVMs and three power

supplies can be used to induce a ground potential difference between EVM1

and EVM2.