Designers of battery-powered medical devices, wireless sensors, RFID tags, intrinsically safe devices, and consumer electronics require low-noise power sources as well as precision measurement capability. So, too, do engineers characterizing new low power semiconductor devices. That’s according to Bob Green, senior market development manager at Keithley Instruments.
To help meet the challenges such engineers are facing, Keithley Instruments Inc. today introduced the Series 2280S precision measurement, low noise, programmable DC power supplies.
Green outlined how products have evolved to make instruments like the 2280S Series useful in their design. A key spec, of course, is battery life, and Green pointed out that a Galaxy 1 phone offered 75 hours of standby power. The S4, in contrast, offers 370 hours. Operating modes have become more efficient as well. He pointed out that an Android 4.4 offered 345 minutes of Wi-Fi browsing; the Android L offers 471 minutes. And medical devices have evolved to make power a key consideration as well. The 1950s era pacemaker, worn outside the body, has given way to implantable devices for which battery life is critical.
While devices like cellphones and pacemakers have low-power sleep modes, they may draw considerable current when active. An LTE phone in sleep mode may draw 38 mA in sleep node but 580 mA when active, Green said, and an implantable defibrillator may draw 0.5 µA in sleep mode but a 5,000,000-µA pulse when active.
In addition to cellphones and defibrillators, low-power design challenges extend to deep brain neurostimulators, gastric stimulators, cochlear implants, and insulin pumps as well as tablets, RFID tags, GPS devices, and wireless entry devices.
In all cases, designers must answer two questions, Green said. First, is the standby current low enough to meet power life specifications? And second, is the stimulation current within specification to minimize power consumption? Answering these questions can require performing low-current measurements with filtering over many power-line cycles, and it can require synchronized pulse measurements over a very short period of time—with fast response to load changes.
Green said that unlike conventional power supplies, the Series 2280S power supplies are also sensitive measurement instruments with the speed and dynamic range essential for measuring standby current loads and load current pulses.
Instrument specs
Series 2280S supplies can output up to 192 W of low-noise, linear regulated DC power. The Model 2280S-32-6 can output up to 32 V at up to 6 A, and the Model 2280S-60-3 can output up to 60 V at up to 3.2 A.
Unlike conventional power supplies, Series 2280S supplies can make voltage and current read-back measurements with up to 6½ digits of resolution for maximum precision or as low as 3½ digits for greater speed. Voltage output measurements can be resolved down to 100 µV. Load currents from 100 nA to 6 A can be monitored with high accuracy. Four load-current measurement ranges (10 A, 1 A, 100 mA, and 10 mA) support measuring full-load currents, standby-mode currents, and small sleep-mode changes precisely.
For monitoring fast-changing and pulse-like load currents, Series 2280S supplies can capture dynamic-load currents as short as 140 μs to monitor load currents easily in all operating modes for determining total power consumption of the device. They also support measuring each state of a power-up load sequence and a power-down sequence. Measurements as fast as 2,500 readings per second make it possible to characterize and test the current draw at each of the start-up states.
Series 2280S users who need to test devices or systems with high in-rush currents can program the voltage output’s rise time to slow the voltage ramp and avoid voltage overshoot, which could potentially damage the DUT. Voltage fall time is also programmable to prevent a fast ramp down of the output voltage.
The 2280S includes 4.3-inch thin-film-transistor (TFT) screen. Source settings and other key information appear next to the measurement readings, reducing the chances of operator confusion and test errors. Soft-key buttons combine with a navigation wheel to provide an intuitive user interface with shallow, easy-to-navigate menus. The icon-based main menu simplifies configuring tests.
The power supplies’ graphing function simplifies monitoring the stability of the load current, capturing and displaying a dynamic load current, or viewing a start-up or turn-off load current. These power supplies can store up to 2,500 measurement points and compute statistics on the stored data. Statistical calculation options include average, maximum, minimum, peak-peak, and standard deviation.
Series 2280S supplies are equally suited for bench-top and automated testing. The built-in List Mode function simplifies testing a design over its operating voltage range automatically or studying how the design responds to DC output changes. Up to nine lists of sequenced voltage levels can be created and saved with up to 99 distinct voltages in each list. A single trigger will automatically execute the list once or multiple times. To minimize test times in automated systems, an external trigger input allows hardware synchronization and control by other system instruments.
In addition to built-in automated features, Series 2280S power supplies feature KickStart Instrument Start-up Software, which makes it easy and quick to set up automated acquisition of large amounts of data.
GPIB, USB, and LXI LAN interfaces offer additional options for programming and controlling Series 2280S supplies. The LXI Core compliant LAN interface and built-in web page support remote control and monitoring, so test engineers can always access the power supply and view measurements.
A choice of front- or rear-panel terminals enhances connection flexibility. For maximum voltage accuracy, rear panel, four-wire remote sensing ensures that the output voltage programmed is the level actually applied to the load.
Model 2280S- 32-6 (32 V, 6 A) and Model 2280S-60-3 (60 V, 3.2 A) each cost $1,990.