This test board contains two TJA1100 ethernet tranceivers, the first device is the DUT(Device under Test) and the second one is a reference device. Both devices are controlled via a graphical interface(GUI). Via this interface pinstraping, register controll and MII comunication can be executed. For stand alone controll every device has an mictrocontroller, the executed secuence can be programmed via the GUI. Multiple register settings can be exectuted, via the GUI supply currents and outout voltages can be measured of both devices.

Both TJA1100 devices are controlled via a microcontroller, this microcontroller contains a MII and I2C interface.
Via an I2C bus de microcontroller will comunicate with the USB PC interface. The board is supplied via a 12V mains adapter, the 12 V is directly used vor TJA1100 battery supply. An DC/DC buck converter will generate 33 out of the 12V, a lliniair regulator will take care of the 5V VCC. All TJA1100 supplies are monitord via an highside current monitor, the I/V translation is converted via an 16 bit ADC. The current measurement of both devices can be done via PC software, its easy to cdompare differences in current between DUT and reference device. TJA1100 has a configuration option called pinstrapping, via pinstrapping TJA1100 can be configured with a e.g phy address. On board is a 512kb EEPROM, thi smemeory contains configuration data during software start-up, also it can contain MII sequences so the board can be used stand alone(without PC connection).

Toplevel scheamtic of TJA1100 functional test board.

The board is supplied via a standar mains to 12V adapter. The DC/DC converter has an switchable ON/OFF led. For some measurements it is necessary to switch of all on board LED’s. The 5k6 resistor is the feedback ratio and will determine the output voltage.

For DCDC converter a TI TSP5430 is used. This buck converter will generate the 3V3 supply for DUT and refererence device. The VCC 5V supply comes directly from the 12V supply via a liniair regulator. The VCC current is low and therfore also the dissipation so a heatsink is not needed.

For current measurent a series resistor is added in the supplyline. The voltage drop is measured via an INA214 high side current monitor. The IN214 amplifier has a gain of 100 to keep the Vdrop lof. The I/V conversion is measured by a 16 bit ADS1115 Analog to digital converter. Both TJA1100 has a current measurent circuit so values can be compared to check for abnormalties.

The TJA1100 INH output is used to controll perepherals, mostly powersupply units. The INH output is a switch inside TJA1100 to the battery pin. Depending on the mode the INH pin is switched to battery or just floating, this pun can be used to switch on/off supply units that is not used during low power mode. Current out of this pin will be additional current into the battery pin(Vbat). To minimize this current INH is monitored ia an LED switched via two MOS transistors, the LED current will now pulled out of Vbat(supply entrance of current monitor). The gate-source protection D1 is in cade the Vbat voltage will exceed 15V.

Both TJA1100 devices have a microcontroller, the microcontroller is used to translate bytes via I2C bus into MMI. MII is a two wire interface so the shared MDIO is bufferd via a 74UP1GT125 tri-state buffer and connected to a seperate input/output pin of the microcontroller. The added conectors ore used for debugging/test and flashing the controllers.
The dipswitch is used to run a MII sequence programmed in the EEPROM. The setting sill determine the executed sequence so the device can be analyze in a defined setting.

The wake pin has two functions, to wake up the device in low power mode or to controll an LED, depending on TJA1100 configuration. As LED output the pin is an open drain and low active. LED D5 will monitor the LED/Wake pin , Q6 is needed to switch all LED’s off during some analysis. If the pin is configured as a Wake-up pin the pin will be toggled via buffer U24A, if not used this buffer will be tri-state. For EN and RSTN pin there is the same construction, the LED’s will no be only monitoring the status of these pins.

To wire up two devices a termination is placed on the board as decriped in TJA1100 application note.

Pinstrapping is used to configere TJA1100 e.g. phy address. Pinstrapping means that certain multi purpose pins are pulled low or high during booting of TJA1100. Bootup is only done durring power up the device, therefore battery and 3V3 supply can be switched off and on to reboot and reconfiger TJA1100. Because of mulipurpose use of these pins a Tri state buffer is used with 10k series resistane. The buffer is needed to disable output pins after pinstrapping, the resistor is needed to limit the load during data communication. Other output pins are used to control the LED’s, wake and others .