POWER


Accurate Voltage Regulation at 24A By Frederik Dostal, power management expert, Analog Devices


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here are many different power supply ICs for a wide variety of applications. However, there are cases where a unique power supply is required. A device such as this was not available until recently. In the communication sector, such as optical transceivers, memory applications and industrial applications, very precisely controlled voltages can be required at high currents.


Use cases


Optical transceivers in particular require a unique power supply. Load transients must also be regulated quickly so that the supply voltage deviates only slightly from the nominal value. All in all, a challenging task for a power supply. Figure 1 shows the application of an optical transceiver in a communication system or data centre.


Usually, such applications have a special requirement for the accuracy of the supply voltage. The switch-mode power supply (SMPS) shown in Figure 1, which generates the voltage for the optical transceiver, works according to the buck principle. It has a DC accuracy of ±0.25 per cent over the entire permissible temperature range of –40°C to +150°C when the output voltage is set between 0.6V and 1.375V. The high temperature range is necessary because data centres have a very high power density and thus generate high losses despite highly efficient voltage converters. These increase the temperature of the circuit to very high values.


For accurate control, it is important to ensure high accuracy for load transients in addition to DC accuracy. These can be achieved with a fast control loop of the voltage converter and with many high- quality output capacitors. Since these capacitors are cost-intensive and take up space, attempts are made to speed up the regulation of the power supply IC. In the LT7176, as shown in Figure 2, this fast control is achieved by a controlled on-time valley current-mode control. Compared to


Figure 1


other solutions, an approximate 30 per cent reduction in the overshoot and undershoot of the output voltage can be achieved due to load transients.


For the lowest electromagnetic compatibility (EMC) interference and highest converter efficiency, Silent Switcher technology from Analog Devices is used. This enables fast switching transients with very low radiated emissions. The fast switching transitions lead to low switching losses of the SMPS and thus a high switching frequency of up to 3MHz with very high converter efficiency is possible.


To further reduce the output voltage ripple of the LT7176, there is an LT7176-1 version. This device is very similar, but offers two phase- shifted channels with the same maximum output current of 24A. However, two inductors are required for this solution. Such inductors, which need only be designed for half the power, are available with a lower overall height and can be helpful for applications that are limited in height.


In addition to accurate voltage regulation, high reliability of volt-age conversion is


important. Through a digital connection of the LT7176, the state of the input and output voltage, the input current, the temperature of the silicon, and other fault states can be queried. It is also possible to execute various settings of the device through the existing PMBus connection. This includes setting the output voltage, a current limit, switching on and off, soft start and soft stop, and many other parameters up to control loop compensation.


Figure 3 shows the graphical user interface LTpowerPlay, which is available free of charge from Analog Devices. This allows the circuit to be evaluated and various settings can be made.


Conclusion


Despite the many different switch-mode power supply ICs on the market, there are always applications where only something very unique can fully meet the requirements. The LT7176 and LT7176-1 present a new solution offering high output currents and control accuracy with low converter losses and low radiated emissions, as well as advanced


Figure 2 14


Figure 3 SEPTEMBER 2026 | ELECTRONICS FOR ENGINEERS


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