How do integrated switch controllers improve system energy efficiency?

Efficient use of resources is essential to achieving sustainable development goals. We can use resources efficiently in many ways. A simple way is to turn off electronic devices when not in use to avoid unnecessary energy consumption. Another effective way is to achieve efficient and reliable design by implementing energy-saving mechanisms.

Switching controllers, especially those that can act as battery freshness seals, are a powerful aid in achieving these goals. Such controllers disconnect the entire circuit from the battery when it is not in use, helping to extend battery life and conserve energy. This not only prolongs the shelf life of the product, but also minimizes standby power consumption, reducing unnecessary battery discharge and thus reducing energy waste.

The following sections describe how these controllers help save energy through their operating modes, integrated features, and robustness.

A common problem with consumer electronic devices is that off-the-shelf products often run low on batteries, requiring recharging or replacement before use. This represents inefficient use of energy and a compromised user experience.

To address this issue, efficient battery-powered devices employ low-power loss circuits or use battery freshness seals. A battery freshness seal is a function of the switch controller that prevents battery discharge by disconnecting the battery from the downstream circuitry until it is connected after receiving a circuit enable signal (e.g., from a button), as shown in Figure 1. This circuit operating mode is often referred to as shipping mode or standby mode, with the latter being more general and the former being used specifically to describe the state of a product before it is used for the first time.

However, even with a battery seal, the battery will slowly drain, causing system efficiency to suffer. The extent of the drain depends on the circuit’s standby power consumption. Devices with lower power consumption can help solve this problem. For example, push-button controllers with battery seals, such as the new MAX16169, have a standby current rating of only a few nanoamps, as shown in Figure 1.

When the button is pressed, the battery is connected to the load. In the example of Figure 1, the battery is connected to a microcontroller (MCU), a secure digital (SD) module, and a global positioning system (GPS) module. In addition, the sleep mode in the MAX16163/MAX16164 can also help to further extend battery life. These devices periodically turn the system on and off at specific times, waking up the devices in the system periodically, and then entering sleep mode again after they complete their tasks. This feature is very useful for wireless monitoring applications such as the Internet of Things (IoT) where devices run intermittently, and can improve overall efficiency by reducing power consumption during standby. Figure 2 shows how power consumption is reduced in sleep mode, that is, the SLEEP_TIMER state; when the battery is connected to the system (as shown in Figure 1), the ACTIVE_STATE appears.

Best practices in PCB manufacturing include responsible resource management. This includes taking steps to reduce invisibility, which means using fewer, smaller, and lighter electronic components in power supplies. This can be accomplished by selecting devices that include multiple functions in a single package, thereby reducing the size of the required PCB and, in turn, reducing the energy consumption of the final product manufacturing. For example, the MAX16150 and MAX16169 in Figure 3 combine load switch and button debounce functions, while the MAX16163/MAX16164 also add timing functions. Note that the block diagrams of the MAX16150 and MAX16169 are very similar.

In addition, the traditional method usually uses a real-time clock, load switch, and button controller to implement it, which is improved by the integrated solution in Figure 4. The MAX16163/MAX16164 integrated solution can not only reduce the solution size by 60%, but also extend the battery life by 20% while maintaining the same functionality.

Incorporating electrostatic discharge (ESD) protection circuits into integrated circuits is critical to ensuring the reliability of circuits in harsh environments. These circuits need to operate continuously and stably, so adequate protection is required to resist external surges. System designers evaluate the anti-static performance of products through ESD test methods, such as the human body model (HBM) method for device-level ESD testing and the IEC 61000-4-2 model for system-level testing.

Device-level ESD testing is designed to ensure that ICs are not damaged by electrostatic discharge during the manufacturing process. HBM simulates a scenario where a charged human body contacts the IC, discharging potentially damaging ESD through the IC to ground. System-level ESD testing is designed to ensure that devices can withstand transient events, including lightning protection, under operating conditions in a variety of real-world applications. To meet this requirement, released products must undergo rigorous testing in accordance with the IEC 61000-4-2 ESD standard, simulating actual transient conditions. Although both HBM and IEC 61000-4-2 ESD test methods simulate scenarios where a charged human body discharges into an electronic system, the IEC 61000-4-2 standard differs from device-level ESD in many ways.

Table 1 shows that the peak current in the HBM test is 1/5.6 of the pulse current in the IEC 61000-4-2 test. In terms of the number of strikes, the device-level HBM test only requires one positive strike and one negative strike, while the system-level IEC 61000-4-2 requires the IC to pass at least 10 positive strikes and 10 negative strikes. This means that in order to achieve the corresponding IEC 61000-4-2 rating, system engineers should consider using devices with much higher HBM ratings. For example, a system with an HBM ESD rating of +15 kV (such as the MAX16150) may meet the IEC 61000-4-2 rating requirement of ±2 kV. Similarly, devices with a +40 kV HBM ESD rating (such as the MAX16163/MAX16164 and the new MAX16169) can help achieve ±6 kV IEC 61000-4-2 compliance.

Table 1. Comparison of peak currents for HBM and IEC 61000-4-2 ESD test methods

The higher the ESD rating, the more resistant the device is to harsh environments. This not only effectively reduces field operation interruptions and improves system reliability, but also reduces the possibility of failure, thereby reducing the cost of frequent product replacement. Analog Devices' switch controllers and battery freshness seals use ESD protection structures on all pins to prevent electrostatic discharge during handling and assembly. In addition, an additional layer of protection is designed at the switch input. The high HBM ESD rating of these seals helps system designs meet the IEC 61000-4-2 standard.

To continue to improve energy efficiency, it is necessary to use devices that can reduce energy waste throughout the process from factory production to field operation. This article describes how ADI's push button switch controllers and battery freshness seals can help reduce energy waste through standby and sleep modes; how to save production energy and reduce PCB size through integrated functions; and how to improve field robustness through higher ESD ratings.