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We are using trying to program an SPI device, but we have a repeated problem – persistent power shutdown to the SPI target device.

Here is a summary of our procedure:

1. Connect the Level Shifter Board with the target chip to the Cheetah SPI Host Adapter, and connect the Cheetah adapter to the USB port of the host computer.
2. Verify the Cheetah host adapter is powered on.
3. Execute the Flash Center Software
4. Run a short test to verify the target device is working correctly.
5. Load the file to the Cheetah host adapter for programming the target device.
6. Run the Flash Center Software to program and verify the target device.

This is the consistent failure:

• During the last step, programming and verifying the target device, power for the target device shuts down.

Our questions:

1. How likely is insufficient power through the USB cable the cause of this persistent shut down?
2. How can we ensure sufficient power is provided to the Level Shifter Board and the target device?
3. Are there other factors to consider?

Thank you for your questions! Persistent power shutdown is a major issue. In the following subsections, checkpoints are listed that could identify and resolve the problem.

Power Delivered through USB Cable

In most cases, using the correct USB cables for devices do not cause power issues. The exceptions:

• The contact of the USB cables to the connectors may be weak or contaminated. In this case, make sure the connectors of the cables and all the equipment are clean and firmly attached.
• To determine if power delivered through a USB cable is insufficient or compromised, connect an external power hub and compare the results.

Effects of Speed and Cables

Although not a power issue, this is another factor to consider with cables.

The Level Shifter Board has been verified to operate up to 18 MHz when shifting to 1.2 V, and up to 20 MHz when shifting to 3.3 V. When operating at higher speeds, shorter cables are recommended to maintain signal integrity. NOTE – the exact bit rate at which the Level Shifter Board can operate per signal level can vary with the conditions of the system setup.

Alternate Power Sources

A Cheetah adapter could be used with an external bus-powered hub that is rated to output 100 mA per port. The Cheetah adapter draws about 125 mA, and reports itself as a low-powered device. The Cheetah adapter can be connected to a bus-powered hub, provided less than 100 mA are being drawn from each of the other ports of the hub. Power consumption per device should be verified. In most cases, other devices connected to the power hub draw less than 100 mA each.

In the case other devices are drawing maximum power from the power hub ports, connect the Cheetah adapter directly to the USB power of the computer, or use a self-powered hub.

The Level Shifter Board draws 6 mA when configured to power the target device. This does not include the effect of the target device. For more information, refer to the section Power Consumption in the Level Shifter Board User Manual.

We hope this answers your questions. Additional resources that you may find helpful include the following:

• Cheetah SPI Host Adapter User Manual
• Flash Center Software User Manual
• Level Shifter Board User Manual
• SPI Background

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.