Figure 5-1: Transistor driver unit frontplane
Description:
The TRNDR unit contains two programmable drive circuits. The controlled, programmable voltage source unit switches between two programmed voltages. The switching time of the electronic switch is about 1ms. The controlled, programmable current source switches between a programmed current value and zero. The switching time is about 1ms for switching off and slightly worse for switching on. Switching times can be longer if the DUT has longer own electrical transient times.
These two units can be used if the sensor/actuator on the thermal test chip is a BJT or a power MOSFET. In this case the current source provides a constant emitter (source) current. The controlled voltage source provides the UCB (UDG) voltage. The dissipation step is IE*DUCB, according to the maximum values in Figure 5-2 DPmax @ 20W can be achieved with this module. With a power booster unit (placed in a separate box) the current range can be extended to 20 A and so DPmax @ 200W can be achieved.
Both power driver units are provided with a 3-state panel-switch, marked LOW/PC/HIGH for the voltage source and OFF/PC/ON for the current source. The electronic switches (see Figure 5-2) are controlled by the PC only if this panel-switch is in PC state. This way the previously programmed voltage and current levels can be steadily set for these sources, depending on the required measurement arrangement.
LED indicators on the front panel show which actual voltage/current setting appears on the output. Green lights indicate LOW or OFF state while red lights indicate HIGH or ON state.
Figures 5-3 shows the safe operating area (SOA) of the programmable voltage source at an ambient temperature of 25ºC and below. For higher temperatures the maximum current load should be reduced as follows:
Imax = 2 - 0.04(Tamb -25)
(currents in amperes, temperatures in centigrades)
Figure 5-2: Controlled sources of the TRNDR unit
The safe operating area of the programmable current source unit is presented in Figure 5-4. As it can be deduced from the diagram the driven current output goes to ± 6 V if left open. For higher temperatures the maximum current load should be reduced as calculated by the formula above.
When using the TRNDR unit always check first the device characteristics sheets for maximum device ratings. Check the measurement circuitry thoroughly before starting the measurement.
NOTE: Do not short UCB source for more than 10 seconds if T3Ster is operated above 25ºC!
For all suggested measurement arrangements the operating software supervises the programmed voltage/current values and prohibits the violation of these safety limits.
Figure 5-3: The safe operating area for the voltage source (Tamb
< 25ºC)
Figure 5-4: The safe operating area for the current source (Tamb
< 25ºC)
For enabling measurements on n-type and p-type devices UCB can be programmed between ±10.24 V. IE appears on one of the connectors only, i.e. IE+ provides the current flowing out and IE- provides current sinking. The other IE connector goes to a high impedance state. (A typical application for using IE+ is measuring p-type devices, while IE- is typically used for n-type devices).