Tektronix TDSUSB2 User Manual

Reference Inrush Current
Inrush Current
Inrush Current is calculated by recording all the current values above the 100 mA current level throughout
the signal. This signal is integrated to get the total charge greater than 100 m A for all inrush regions in the
signal. This
is the charge in Coulombs and is calculated using the integral of:
idt
Where:
i is the current waveform above 100 mA.
Capacitance is calculated by using the equation:
Where:
C is the capacitance.
Q is the charge.
V is the voltage.
The supply voltage is one of the inputs to Inrush measurement.
Measurement Method
Inrush current is measured for a minimum of 100 milliseconds after attach. Attach is defined as voltage
rising to a valid level on the peripheral’s USB power line. Any current exceeding 100 mA
during the
100 ms interval is considered part of the inrush current event. The inru sh current is divided into regions. A
region is an interval where the current exceeds 100 mA until the time the current falls below 100 mA for at
least 100 μs. There can be multiple inrush regions during the 100 ms period. Pass/fail is determined by
the region having the highest charge.
182 TDSUSB2 Universal Serial Bus Measurements Package

Tektronix TDSUSB2 Specifications

General

Brand	Tektronix
Model	TDSUSB2
Category	Measuring Instruments
Language	English