When is a multichannel power supply more convenient than a single-channel power supply?
Are you creating a device that has both digital and analog circuitry or bipolar circuitry? If so, a multichannel supply is the more convenient power source. Triple-channel power supplies typically have two higher voltage channels for analog circuits (to power multi-voltage circuits or to create bipolar power supplies for testing bipolar analog circuits) and a third channel intended to power a digital circuit. The voltage for this third channel is typically 10V or less (for testing digital circuits operating at 5V or less). Pay close attention to how the power supply’s vendor specifies that channel. Some supplies have fixed (i.e., non-programmable) voltage output channels, which are often 5V channels. However, if the application requires testing digital circuitry that operates at 3.3V or 1.8V, a programmable third channel is essential.
Does your DUT require individual isolated power supply sections? If so, you will either need to configure multiple isolated supplies (which can be both expensive and less convenient to operate) or buy a multichannel supply. However, be aware that multichannel units can either have isolated outputs or they can have output channels that are tied to a common point on their low side. When the channels are connected with the same common point, they aren’t suitable for powering circuits that are isolated from each other. For example, medical monitoring devices have circuits that are in direct contact with patients. Those circuits use a reference point that is isolated from the earth ground-based circuitry on the power line side of the device. This is also true for devices that use opto-isolators to create separate, independent common reference points for different analog circuits or analog and digital circuits. For these applications (Figure 1), look for multichannel supplies with isolated outputs.
Do you need tracking functionality? During circuit development, it’s essential to confirm the circuit operates within its performance specifications over its defined voltage operating range. Multichannel supplies with tracking functionality offer a convenient way to test a bipolar circuit by linking both channels (a positive-configured output and a negative-configured output) so they change synchronously with each other (Figure 3). Although some multichannel power supplies can track only with both channels outputting voltages of the same magnitude, newer offerings, such as the Keithley models 2220-30-1 and 2230-30-1, allow tracking with a variable ratio between the two channels.
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Keithley’s Application Note, Ensuring that Power Supply Performance Meets Your Requirements.