The VDLM 1710X3801 fulfils the requirements of many diverse applications.
By Timur Uludag, Product Manager for the MagI3C Power Division at Würth Elektronik.
The current trend in the field of DC/DC power modules has been moving away from specialization and toward a “generalist” approach. This means that the power modules no longer have just one standout feature that they need for use in a specific application, but instead have a bouquet of features, thereby making them appealing for a wide range of applications.
Non-isolated miniaturized DC/DC converter power modules are used in a wide variety of applications that are deployed in a wide range of environments, including security and surveillance, smart home systems, and medical equipment. Each application has specific requirements for the supplying DC/DC converter. The main requirements for these types of converters can be summarized into the following four categories:
• Wide input voltage range.
• Adaptive switching behavior.
• High efficiency.
• Power sequencing.
Let’s consider some of these aspects in a little more detail.
Wide input voltage range
The input voltage range of the aforementioned applications extends from a 5V point-of-load (PoL) supply via a 12V intermediate voltage, generated in the device itself, for a direct connection to the 24V DC bus.
Each rail voltage has its own tolerance range. If one were to use a separate DC/DC converter for each rail voltage, the respective design would have to be conceived, configured, tested, checked for EMI conformity, built, and logistically handled.
The VDLM series 171013801, 171023801 and 171033801 come with an input voltage range from 3.5V to 38V. This makes these power modules suitable to cover all common voltage rails.
Adaptive switching behavior
Many applications can benefit from DC/DC converters with the ability to address varying power demands. For example, a measurement application has a higher power demand while taking a measurement and a lower power demand between measurements.
- Light load, in which the application operates in idle or standby mode (reduced energy consumption).
- Full load, in which the application operates under nominal conditions (normal energy consumption).
Pulse-width modulation (PWM) and pulse- frequency modulation (PFM) are techniques used to represent analog signals using only two levels (0 and 1). PWM maintains a constant frequency while varying the duty cycle of the 0 and 1 values, while PFM maintains the same duty cycle while varying the frequency. PWM is widely used in most industrial power supplies. This mode is satisfactory for these types of industrial applications that work in heavy loadconditions for most of their operating lifetime. By comparison, in light load conditions, PFM offers improved efficiency Both of these modes are supported by the 1710X3801, with any transitions between modes Different switching behaviour under different load conditions—PWM mode under full load (Left) and PFM mode under light load (right) occurring automatically depending on the current value of the load current.
Influence of efficiency
How does the efficiency of a power module affect an application that is supplied by a battery? An example with a 2,800 milliampere-hour (mAh) battery illustrates the importance of high efficiency for battery life.
Example calculation:
- Battery with 2,800mAh capacity.
- Application load current of 10mA.
- Output voltage power module of 1.8V.
Assuming three different DC/DC converters with efficiencies of 20%, 45%, and 85%, the lifetime of the battery would be 112, 264, and 480 hours, respectively. To look at this another way, the battery duration of a system using a DC/DC converter with 85% efficiency will be extended by more than 400%. The 171013801 features a peak efficiency up to 96%.
Power losses and thermal derating
Another impact of higher efficiency, especially relevant in space- constrained applications, is a lower temperature rise of the converter. The figure on the next page illustrates the derating comparison between a low-dropout regulator (LDO) and a VLDM 171013801.
In particular, it shows the negative influence of the power dissipation on the output current capability of the LDO (the LDO used in the comparison is rated for VIN = 40V and IOUT = 1A).
Due to the low efficiency of the LDO, the derating happens pretty early, being only capable of supplying 0.1A instead of 1A. In contrast, the VDLM 171013801 has no derating up to 105°C, with an output current of 1A for VIN = 24V to VOUT = 5V. Running at high temperatures results in less reliability, additional design effort, and increased cost due to things like heat sinks.
Power sequencing
In systems with the demand for multiple rail voltages like microcontroller units (MCUs) and digital signal processors (DSPs), the voltages must be applied in a defined time sequence.
The figure to the lower right illustrates three voltages— shown as V1, V2, and V3—that need to be applied to the load (e.g., a DSP) in a defined time sequence.
To realize this type of power sequencing, the power module needs two features that support this:
- Enable feature: This sets the converter to start switching when the threshold is reached.
- Power Good feature: Once VOUT reaches a certain threshold (e.g., 90%), the PG pin transitions to a high state.
One size fits all
In this context, the phrase “one size fits all” refers to one DC/ DC power module solution that fulfils the requirements of many applications. The VDLM 1710X3801 supports this strategy in two ways. First, the pure performance data covers many applications, from the low-power range to the mid-power range, whether it is a PoL application or a 24V DC bus application.
- VIN = 3.5V to 38V.
- IOUT = up to 3A.
- VOUT = 0.85V to 13V.
- LGA-12EP package.
Second, the use of an integrated power module that can be easily inserted into an application as a ready- made solution provides a remedy here. The VDLM 1710X3801 power module comes fully tested in all areas that are essential for a DC/DC converter.