Figure 5-7: Power switch & thermostat driver frontplaneand module detached
Description:
The SWTDR controlled power switch is devoted to be used with conventional thermal test chips where a resistor serves as dissipator. In this case an external DC power supply has to be used and the T3Ster equipment is responsible only for the fast switching on/off of the current. The ratings of the built-in electronic switch are 50V and 2A - thus dissipation-step values can be realized up to 100W. With a power booster unit (placed in a separate box) this range can be extended to 50V and 20A, that means up to 1000W (on special request a power driver unit with even higher ratings can be ordered). For details on the power booster unit refer to section 7.5.
Figure 5-8: Functional scheme of the SWTDR circuitry
Using the controlled switch, the voltage is measured by the 4-wire method (Figure 5-8). Both the current and voltage on the switch are measured by two internal A/D converters in the measurement units of the SWTDR and are read by the computer.
Figure 5-9: Using the SWTDR module for standard measurements
The SWTDR module has two 25 pole D SUB connectors, JP1 for measurement control and JP2 for thermostat control.
In Figure 5-9 a typical measurement (up to 50 V 2 A) with no external power driver is shown. Numbers in italic correspond to pin numbers on JP1 (see also Table 5-A). Unconnected pins have no role in standard measurements.
| Pin | Signal | Description |
|---|---|---|
| 1 | GND | See Figure 5-9 |
| 2 | Gate drive | |
| 3 | Gate in | |
| 4 | Force L | |
| 5 | Isense H | |
| 6 | Isense L | |
| 7 | Sense L | |
| 8 | Sense H | |
| 9 | GND | |
| 10 | Force L | |
| 11 | Force L | |
| 12 | Force H | |
| 13 | Force H | |
| 14 | Force H | |
| 15 | Force H |
Table 5-A: JP1 connector, measurement control 25 pole D SUB female
| Pin | Signal |
|---|---|
| 1 | DGND |
| 2 | D1 |
| 3 | D3 |
| 4 | D5 |
| 5 | D7 |
| 6 | D9 |
| 7 | D11 |
| 8 | Thstate A |
| 9 | D0 |
| 10 | D2 |
| 11 | D4 |
| 12 | D6 |
| 13 | D8 |
| 14 | D10 |
| 15 | Thstate B |
Table 5-B: JP2 connector, thermostat control 25 pole D SUB male
The external thermostat has an autonomous control. Programmed temperature values are sent to the thermostat in 12 bit data words (D0 to D11), two bits are sent back to the SWTDR unit representing the presence and status of the thermostat (Thstate A and Thstate B). The pinout of JP2 is summarized in Table 5-B.
The SWTDR module contains a DVM unit consisting of a differential input attenuator and an A/D converter. An external analogue signal can be connected to the DVM input and can also be processed in the computer. This input serves mainly measuring the voltage on the dissipating element in several measurements. The input connector may vary in different appliance models.
The DVM input is differential, this means the outer barrel of the connector should not be connected to a grounded point if not explicitly prescribed in the Application Notes.
The DVM unit has the following specification:
The SWTDR module also controls the external power booster unit through the signals of JP1.
The SWTDR module is provided with a 3-state panel-switch: OFF/PC/ON. The electronic switch is controlled by the PC only if this panel-switch is in PC state. This way the ON or OFF states can also be manually switched, depending on the required measurement arrangement.
LED indicators on the front panel show the actual switch state: the red light indicates the ON while the green light indicates the OFF state of the switch.