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Texas Instruments: achieving a more compact power solutions

In Electronic Infomation Category: R | on July   10, 2011

This article details the latest developments in the power circuit. The paper also describes several devices, Yue Ming circuit packaging technology advances in architecture and IR2110PBF datasheet and how to promote more compact power solutions.

Of different functions into one chip is a PDA, portable navigation systems (GPS) and IR2110PBF price and smart phones and IR2110PBF suppliers and other portable products, trends. Just a few years ago, applications of each group will need a separate power supply converters, battery-powered products but with the increasingly complex functions, power supply design have begun to change, the integration of products required in various power together has become a trend, in addition to the processor power required, there are Bluetooth modules, wireless network module and screen and other features also need a separate power supply. In such applications, the power supply can be divided into several:

· Other functions with embedded power supply chips, such as CODEC, ADC, audio amplifiers and chargers

· A single chip to provide all the power

· Modules dedicated power converter

This article describes the last two solutions. Functional modules used in the design of a dedicated power converter has several advantages: First, position the board easier to arrange the parts as they can be placed directly on the processor power or wireless network module next target. Second, the circuit board layout easier, because the signal is not across the whole board. In addition, the power supply and other circuits will also minimize the coupling between, this GPS module or phase-locked loop (PLL) and so the sensitivity of the power of particular importance.

This approach for the solution based on existing product development plans follow-up is also good, because when the engineer to change the product design, they can be confined to changes in the functional module level - designed to upgrade only need to modify the function part, other circuits remain unchanged; contrast, if the application is only one power chip, engineers must spend more to meet the new requirements of the spirit to the design. Because shortening product development time has become critical to the success of such methods is clearly the power supply has a considerable edge.

To provide this solution, power chip must meet several requirements. First, there must be a variety of devices to provide the necessary power, and its size must be minimized to avoid taking up too much board space. Second, these chips should be very easy for different needs with different solutions. Texas Instruments (TI) of the TPS6502x and TPS6505x series are examples of these devices specifically for the handheld devices applications processor to provide power. The different series of processors have different needs, they also have exclusive models of the chip to support the individual or individual family of processors and applications.

In general, the application will be required to use battery power to a large range of output current to maintain high efficiency, all components of the operation must be optimized for the quiescent current. The so-called quiescent current is the chip does not provide any output current in the case, the output voltage required to maintain the current, the parameters of Bi Xu Zhang Shijian application in standby mode is very important. Low quiescent current standby time not only to extend the application of DC power converter output current under the low efficiency is also greatly affected.

DC buck converter power converter efficiency will be affected by three factors: the output current is large, the efficiency of the main power switch from the internal impedance of the decision, so the low impedance of the operating range is very important. For a fixed frequency pulse width modulation (PWM) buck converter, the duty cycle is the ratio of input to output voltage decision. Output voltage is very small, the internal bottom of the switch (NMOS) on-time will be far more than the upper switch (PMOS); If the output voltage is high, it becomes the top switch on a long time. Therefore, if assume that all input voltage converters are the same, the designer should be the goal for the converter output voltage to the size and impedance selector switch; general, portable applications in lithium-ion battery voltage range from approximately 4.2V to 3.0 V, the future may also be further reduced to 2.5V.

When the output current 10-200mA range, the main power source is no longer switch resistance, but by the power switch gate charge and determine the efficiency of inductive power. Control the output current using the switching frequency operation in this important range of skills to maintain high efficiency, this approach known as pulse frequency modulation (PFM). PFM will provide essentially fixed to the output of power: the output current is large, relatively high switching frequency, output current low switching frequency is reduced, thereby reducing switching power. Converter output current is very low, due to the fixed-power quiescent current to determine the overall efficiency mentioned earlier.

TPS6502x and TPS6505x family the best of all devices are low-power design, it can be to a large range of voltage and current to provide the highest conversion efficiency. Table 1 TPS502x series of profiles, the device includes three of buck converters, which provide system voltage, memory voltage, and processor core voltage; They also contain two low dropout linear regulator (LDO), responsible for providing power to the phase-locked loop (PLL) and SRAM or other processor modules. There are many features of these devices not listed in the table, for example, battery backup support, I2C interface and reset functions.

Table 1: TPS6502x Series Overview 1-3

converter output voltage can be adjusted by an external resistor divider, LDO voltage from two digital input pin settings. In addition, all switches and two LDOs output voltage through the I2C interface settings.

If the application processor requires more power, can also choose TPS6505x series. The device consists of two buck converters and four high power supply rejection ratio (PSRR) of the LDO. LDO can supply power to the modules that require low noise, such as PLL, GPS modules or wireless network module. TPS6505x series of packages is small, and only few external components, it can design the minimum power supply solutions. TPS6505x series in a compact 4x4 mm QFN package, lead pitch of 0.4 mm, and up to 32 the total number of pins. So many pins and the bottom of the cooling pad QFN package, so that excellent thermal performance TPS6505x series into a highly integrated solution.

Figure 1: TPS65052 structure diagram

Figure 1 is a block diagram of TPS65052. The device is designed to support Samsung Electronics (Samsung) application processor, they need to 1.0V core voltage low-power mode, the normal mode of operation requires 1.3V voltage. In order to minimize external components, this device will provide a buck converter output voltage to 3.3V fixed I / O use, the converter 2 is responsible for providing the core voltage, and the output voltage can be set to 1.0V or 1.3V specific settings, as DEFDCDC2 digital input pin on the status of, so no external components to set the voltage step-down converter. LDO is true, the device will interpret the internal forms such as 4 DEFLDO1 to DEFLDO4 the state of digital input pins, and then interpret the results according to set LDO output voltage. LDO in the 4 groups, 3 groups with independent input voltage pin, an acceptable anywhere between 1.5-6.5V input voltage. The LDO can accept different power supply, in which a group can be battery, the other from the buck converter can be 1 or any of the available power within the system. Engineer should choose the lowest input voltage LDO, which can optimize the design to achieve high efficiency. This series of other devices through an external resistor divider can set the output voltage, to ensure more flexibility in application design. Table 2 is the TPS6505x series of options.

Table 2: TPS6505x series of options

Addition to step-down converter and LDO addition, TPS6505x series also includes a comparison with a 100ms delay device, when it found that the input voltage reaches the 1V threshold, will be in the drain Reset signal output pins have open; In addition, it set the comparator pin movement through the lag time. Designer as long as the comparator output is connected to any one of the converter or LDO enable pin, will be able to start when the voltage exceeds a critical value of the LDO or the converter. TPS6505x allows designers only a very small chip, and can create 6 different power supply and processor reset signal.

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