Keithley 2032 Power Supply WP free download

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WHITE PA P E R Power Supply Transient Response Considerations When Testing Portable Wireless Devices Kevin Cawley Keithley Instruments, Inc. Introduction Designers of today's portable, battery-powered electronic equipment, such as cellular telephones, pagers, two-way radios, personal digital assistants, and other communication devices are constantly striving to provide greater functionality and higher speed in smaller packages. At the same time, they want to offer longer operating periods between recharges. As desirable as these capabilities are from the consumer's perspective, they pose new challenges for device manufacturers' production test engineers. For example, the trend toward lower voltage circuitry and longer operation between recharges are driving efforts to decrease in the minimum battery voltage at which a device will operate (before it automatically turns itself off to prevent damage.) With device power levels remaining the same or increasing, operating currents are increasing. Therefore, to conserve power, today's portable electronics typically operate in pulse fashion and most devices enter the "idle" mode when not being used. This requires the device to switch quickly into "operate" mode to perform a function and then go back to idle mode when not immediately needed. For example, a cellular phone that's not being used will be in stand-by mode, then switch itself on to transmit, then switch back to standby. During these transitions from one mode to another, it's not uncommon for the load on the battery to change from tens of milliamps to several amps in just 20 to 50 microseconds. This means that test systems must include power supplies Keithley Instruments, Inc. capable of responding quickly to transient load changes. 28775 Aurora Road Cleveland, Ohio 44139 (440) 248-0400 Fax: (440) 248-6168 www.keithley.com A G r e a t e r M e a s u r e o f C o n f i d e n c e Pulse Operation In Cellular Phones To maximize the cellular phone industry's message capacity (the number of user