Ultra-small step-down DC/DC converter with integrated coil

As mobile phones , smart phones , portable game consoles, digital cameras, PNDs and other portable electronic products develop towards multi-functions and miniaturization, higher and higher requirements are placed on power management. Especially when powered by batteries , how to effectively use batteries and extend battery life has become the focus of everyone's attention. Therefore, power management must have the characteristics of miniaturization and high efficiency at the same time. DC/DC has high efficiency in energy conversion, but the external coil often takes up a large part of the space, which is not conducive to the miniaturization of products; the commonly used LDO is small in size, but the efficiency is not satisfactory. The XCL205/206/207 series products recently launched by Torex Semiconductor can solve this problem well.

XCL205/206/207 has the characteristics of DC/DC and the usage of LDO (Figure 1).

XCL205/206/207 is a step-down DC/DC converter and coil integrated IC. It installs the coil above the step-down DC/DC converter XC9235/36/37, while reducing the installation area and ensuring the various characteristics of the step-down DC/DC converter (Figure 2). In this way, XCL205/206/207 only needs two ceramic capacitors outside to have the high efficiency of the DC/DC converter and a simple circuit structure similar to LDO , making it possible to combine miniaturization and high performance of the product (Figure 1).

When the lithium battery input is 3.6V, as shown in Figure 1, in order to obtain an output of 1.8V, 300mA, the LDO needs to consume 300mA of battery current. When using MICRO DC/DC XCL205/206/207, only 183mA of battery current is consumed, saving battery energy and significantly extending the battery life.

To simplify production, the XCL205/206/207 series uses a simple structure to form a groove in the center of the coil when the DC/DC converter and the coil are made into one. The XC9235/XC9236/XC9237 series products are embedded in the groove and then bonded and fixed, thus solving the problem of rising costs caused by complex engineering. In addition, with this structure, the electrodes and IC pins above the coil can be directly mounted on the PCB, and the wiring of the DC/DC converter can be implemented on the PCB layout. At the same time, in order to control the total height of the coil and DC/DC converter within 1mm, the DC/DC converter adopts the newly developed USP-6EL packaging technology, with a height of only 0.4mm. The overall dimensions of the XCL205/206/207 are only 2.5mm×2.0mm, h=1.0mm, which is the smallest product in the world (Figure 3).

XCL205/206/207 adopts built-in switch tube synchronous rectification, with a maximum load current of 600mA, an operating voltage of 2.0V to 6.0V, and a fixed output voltage of 0.05V, which can be selected in the range of 0.8V to 4.0V. The switching frequency is 3MHz, and there are three types of operating modes to choose from: PWM control (XCL205), PWM/PFM automatic switching control (XCL206), and manual switching control (XCL207). It achieves fast response, low ripple and high efficiency in the entire load range from light load to heavy load (Figure 4), and the internal circuit stops working in standby mode, and the current consumption can be controlled below 1.0uA.

In addition, XCL205/206/207 has current limiting protection and undervoltage lockout (UVLO) functions. When the input voltage is less than 1.4V, the internal control circuit will be forced to stop working. It also has an output capacitor (CL) automatic discharge function. When the IC stops working, the internal switch is turned on to release the charge of the load capacitor CL, so that the output voltage quickly drops from a high level to the VSS voltage.