SNLA239C Application note

SNLA239C May 2021 – December 2023 DP83867CR , DP83867CS , DP83867E , DP83867IR , DP83867IS , DP83869HM

2.2.1.2 Peak Voltage

Purpose: To ensure correct PHY transmitter output voltage levels.

Pass Condition: Voltage Levels are to be within:

Equation 1.

0.67 V < P e a k V o l t a g e A < 0.82 V

Equation 2.

0.67 V < P e a k V o l t a g e B < 0.82 V

Equation 3.

\frac{P e a k V o l t a g e B - | A v e r a g e o f P e a k V o l t a g e A a n d B |}{|A v e r a g e o f P e a k V o l t a g e A a n d B|} \times 100 % < 1 %

Equation 4.

2 % < 100 % \times (1 - \frac{0.5 \times | A v e r a g e o f P e a k V o l t a g e A a n d B |}{| P e a k V o l t a g e C |})

Equation 5.

2 % < 100 % \times (1 - \frac{0.5 \times | A v e r a g e o f P e a k V o l t a g e A a n d B |}{| P e a k V o l t a g e D |})

Where Average of Peak Voltage A and B is defined as $\frac{P e a k V o l t a g e A + |P e a k V o l t a g e B|}{2}$ .

Specific Test Setup: Verify the correct test fixture connections. Note that some Ethernet compliance software can run Template and Peak Voltage Tests simultaneously.

Note: Some older versions of Ethernet compliance software use an incorrect formula for determining symmetry within 1% between Peak Voltage A and B. This can result in 2x the actual percent value, failing the test case. Hence any failing result needs to be double checked using (3).