These factors need to be considered when building a DPS system that meets specific application requirements!

These factors need to be considered when building a DPS system that meets specific application requirements!

[Introduction]Device power supply (DPS) ICs have flexible voltage drive and current drive capabilities to provide dynamic test capabilities for automatic test equipment (ATE). When the load current is between two set current limit values, the DPS IC can be used as a voltage source; when the set current limit value is reached, the DPS IC can be smoothly converted into a precision current source.

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 1. Schematic diagram of the MAX32010

Figure 1 shows the simplified architecture of the MAX32010 ADI device power supply. Switches FIMODE, FVMODE and FISLAVEMODE select different modes such as FV (voltage drive), FI (current drive) and FI slave selection, while switches HIZF and HIZM select MV (measure voltage) and MI (measure current) modes, respectively. Combined with an external sense resistor, the RANGEMUX supports multiple current ranges, RA (1.2A), RB (20mA), RC (2mA), and RD (200µA). Custom current ranges can be designed by changing the sense resistor value using the formula RSENSE=1V/IOUT. With the CLEN switch and ICLMP and VCLMPDAC, the user can also set the programmable voltage and clamp current.

This article begins with two important considerations when designing a device power IC in a system, range change glitch and efficiency. The article then details some considerations for building a DPS system that meets specific application requirements.

range change glitch

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 2. Comparing scope change glitches between ADI and the competition

Let’s look at the first consideration, the problem of glitches caused by changing the measurement range. When the ATE performs DUT tests, the system may need to change the current range for different tests. IDDQ or quiescent current measurements usually require the lowest current range and are used to measure smaller current values. Voltage spikes or glitches when moving to the lowest current range can not only affect the measurement, but can also damage the DUT. Glitch-free range changes protect the DUT and validate testing. When tested with a 270pF load capacitance, ADI’s DPS was able to perform this transition very smoothly without any glitches, as shown in Figure 2. If no load capacitor (0pF) is used, a transition will occur in 20µs with a ramp rate of 25mV/20µs. This transition produces much smaller glitches than competing products do when transitioning. The competitor DPS had a glitch of 159mV in microseconds. As a result, ADI’s DPS performance is 536% higher than the range change performance of competing products without causing any damage to the DUT.

Device Power Efficiency

These factors need to be considered when building a DPS system that meets specific application requirements!

Table 1. Competitive Analysis of Device Power Efficiency

Device power efficiency is the second most important consideration when selecting a DPS IC, as this factor directly affects the cost and reliability of the system. Higher efficiency leads to greater cost savings, greater reliability, and generally longer system life. A less efficient DPS produces more heat; more heat means more losses, and the failure rate of components in the system becomes higher.

The formula for calculating the power efficiency of a device is, Efficiency = Power Out / Power In.

As shown in Table 1, ADI’s DPS supplies more current (1.2A) with higher efficiency (58.33%) compared to the current supplied by the competitor’s DPS (1A). ADI’s DPS efficiency is 11% higher than Competitor 2’s DPS IC and 155% higher than Competitor 1’s DPS IC.

Now, let’s consider some aspects of building a DPS system to meet specific application requirements.

How to meet custom load current requirements in DPS

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 3. Selecting Custom Load Current Using Sense Resistor

Each ATE has custom load current requirements for each device under test (DUT). The MAX32010 allows a custom range to be selected by changing only 1 sense resistor value. The RANGEMUX in the MAX32010 selects one of the following current ranges: RA (1.2A), RB (20mA), RC (2mA), or RD (200µA). Select the sense resistor value by using the formula RSENSE=1V/IOUT. For example, the load current requirement is 5mA; 5mA is the custom load current, which belongs to range B. To choose the correct RSENSE: RSENSE=RB=1V/5mA=200Ω.

How to increase output current

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 4. Configuring Parallel DPS for Higher Output Current

In many cases, the current required by the DUT may be higher than what a single DPS chip can provide. As shown in Figure 4, additional currents in excess of 1.2A can be achieved by paralleling multiple DPS devices. Both devices remain in FI mode, doubling the current. For example, connecting two 7V, 1.2A devices in parallel can achieve a 7V, 2.4A output current.

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 5. 50% Duty Cycle Pulse Test Output of the MAX32010

To improve the output drive current capability of DPS, another method is pulse output. Pulse testing is a viable option if the current requirement is only for a short period of time, as shown in Figure 5. For example to test the IV characteristics of the DUT. By changing the duty cycle of the FI turn-on time, a pulse test can be performed. In this test, the DPS mode was set to FI mode 50% of the time and to “high impedance” mode the other 50% of the time. Depending on the DUT current requirements, the duty cycle may vary. We performed this experiment on the MAX32010IC and the results are as follows:

Maximum output current = 1.436A, duty cycle up to 50%

How to choose the right cooler for your DPS system

In order to obtain a reliable and stable system, the correct choice of heat sink is necessary. The following example shows a step-by-step guide to selecting the correct heat sink for the MAX32010.

Step 1: Get the relevant dimensions of the package. A package thermal analysis aids in selecting the correct heat sink. It is important to know the area of ​​the exposed pad for heat dissipation.

Step 2: Obtain the PCB thermal properties to calculate the boundary conditions for θJA. Calculate power consumption, taking into account all methods of heat dissipation (conduction, convection, and radiation).

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 6. Temperature distribution of MAX32010 package with heat sink

Step 3: When calculating the temperature distribution of the package, the heat sink base area and the speed of the heat sink fan are two important variables. Remember that the junction temperature of the IC should be kept below the thermal shutdown temperature. Our analysis using still air shows that keeping the junction temperature below 140°C for the MAX32010 requires a heat sink with a base area of ​​30.48mmx30.48mm, a thickness of 5mm, and a heat sink length of 15mm.

These factors need to be considered when building a DPS system that meets specific application requirements!

Figure 7. Thermal Analysis of the MAX32010

Step 4: Airflow and heat sink material play an important role in keeping the IC’s junction temperature below 140°C. Our analysis shows that temperature performance can be significantly improved by increasing the airflow over the copper heat sink by 1m/s.

in conclusion

This article provides guidelines for selecting device power (DPS) ICs in automatic test equipment (ATE) systems. These considerations will help customers select a DPS IC based on their specific ATE system. A system-level architecture capable of meeting the output current and thermal requirements of an ATE system is also described.

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