Using MTM for USB Hub Functional Board Level Test

2015 October 23
Using MTM for USB Hub Functional Board Level Test

Not only do we make Manufacturing Test Modules (MTM), we also use them to test our own products. Using BrainStem® MTM modules to make a functional board level test system is incredibly simple. For the USBHub2x4, MTM allows us to make a test system that requires no external test equipment without compromising on test coverage!

The USBHub2x4 is a programmable USB 2.0 hub capable of switching on and off USB power and data lines independently. It also supports USB Battery Charging Specification 1.2 (BC 1.2), which means each port can supply up to 2.5A to a downstream device. That means the hub can deliver 50W of power, so our functional test system needs to test that the power system in the hub can actually do that. Additionally, the functional test system:

  • Automatically detects Device Under Test [DUT] insertion and starts the test sequence
  • Checks for shorts on all power rails
  • Controls and monitors input power to the DUT
  • Measures base system current before firmware loading
  • Measures total system current under maximum load, and thus checks power system efficiency
  • Runs a "burn-in" test which draws the maximum designed load during the whole test sequence
  • Loads firmware to the microcontroller
  • Checks all LEDs are installed and functional
  • Measures 5V and 3.3V rails, and precision analog 3.3V rail
  • Verifies USB Vbus rail measurements
  • Verifies all downstream USB ports turn on and off independently
  • Verifies both upstream USB ports are functional
  • Measures DUT board temperature rise during burn-in (also a secondary effiiciency check)

The test system is built using an MTM-IO-Serial module and an MTM-USBStem module. With just a cheap, "wall-wart" 12V power supply and one USB cable, the entire test system can be set up in less than one minute. The MTM modules are inserted into a custom test-point carrier board (TPCB) which has only minimal circuitry, making it incredibly cheap to produce. Since the MTM modules are all protected against ESD, over-voltages and short-circuits, the TPCB needs only a "burn-in" resistor and a fan to dissipate the 50W.

To learn more about MTM and building scalable, low-cost, robust manufacturing test systems, contact us.