Now, the majority expenses class and the motion application’s battery are based on the lithium ion technology, like lithium ion, lithium ion polymer battery and so on. This kind of battery has the outstanding capacity performance, and has the 3.3V~4.2V voltage range, this permission realizes the effective power source management with 3V fixed power source’s IC in the system.
Needs to continue along with the IC voltage to reduce makes the operating time to lengthen, now many systems also need the multi-power sources and the more complex power source management function. In order to satisfy these requests, the designers are also familiar with from many suppliers select each kind of ready-made low integrated power source management part, so that rapidly develop products. Often compound circuit’s power source subsystem only contains or two power sources and some discrete component (for example low pressure manostat LDO and the voltage dropping converter).
Certain system designs (are specially portable electronic installation) complex increase, means need more controls, but the designers should consider how to cause the efficiency optimization, does not use the function depending on the closure and when the multi-power sources move guarantees stable and the correct work.
Like this used many discrete components to be already insufficient. Follows is designing complex increase, needs to adopt the system-level method to design the power source management subsystem, in the voltage produces with in the constant voltage basic function, increases the complexity. Depending on increases other component to the existing part set, may satisfy requests like this, moreover does not increase the cost and the PCB area.
Eliminates consideration high integration beyond consideration, but must consider the support program needs entire performance. The viewpoint which manages from the power source, the request considered much the power source management subsystem stipulated function, integrated all functions, but does not affect the technical performance. For example, the typical hand-hold application has the lithium ion power source, the control major function processor, the memory, the exterior peripheral device (for example demonstration), the memory expands (for example SD either the MMC card) and some module function (for example data conversion or sensor connection). Such system acts according to each function the difference, needs some different power sources. The processor usually needs two power source - - one to use in the core nucleus the low voltage (in order to save power loss) and uses in the connection other component’s high voltage. The analogue function needs the high voltage to guarantee the operating region, or provides the powerful output driving force, but along with the demonstration size and complex increase, demonstrated that the driver needs the high voltage.
The integrated power source management subsystem should consider other questions include:
· connection system’s method: Uses the mechanical switch or the electronic method? How does the connection connect the controller (model example is double function switch, it power source and other functions unifies in together).
· battery supply outside field (undervoltage or pressure).
· each power source’s sorting: A multi-voltage’s question is needs first to drive the overvoltage the power source, by against IC block system.
whether · the permanent drive’s power source does need the dormancy function.
· does not remove the battery closure system.
May aim at these questions to use the standard component, like POR (circular telegram replacement) the electric circuit, the battery monitor IC and PLD (programmable logical component). However, the system increases the part to be able to increase the cost and to increase the PCB area.
Power source management subsystem IC
Power source management subsystem IC(PMIC) can integrate more functions, it is in the simple functional device (for example low pressure manostat LDO or the switch switch) and complex system chip IC (contains power source management and so on many functions) between.
PMIC (Figure 1) the goal is provides the core function for the lithium ion power supply portable application, provides the effective work for the biggest battery life. The core function usually is the high efficiency voltage dropping switch and certain low quiescent current LDO.
In canonical system’s PMIC is shown in Figure 2, needs to pay attention to several different exterior question. For example, the power source management needs with the battery (is generally directly single lithium ion power source) the connection, but works time has the controller to produce and to control certain system power source. The system (does not have controller in the simple, but needs many power sources), will add an appropriate battery voltage and enables the signal to start the component, will drive all manostats. PMIC may continue to work, or has the wrong condition until the user with the ONKEY pin shutdown component (for example low battery voltage).
Looked from the control and the programmable viewpoint that are more about the stable output voltage’s choice, the flexibility is bigger. Through the special pin, with the simple control interface to the micro controller is one kind of simple choice, with controls comprehensively through the I2C main line, may provide the programmable output voltage.
Usually, PMIC contains certain LDO manostat, the DC-DC voltage dropping switch and other functions.
The LDO voltage manostat is the power source management system management system’s center section, can other IC produce stably, the low noise supply voltage for the system. The LDO important performance parameter is power source rejection ratio (PSRR) and the quiescent current, the latter immediate influence standby time. Each manostat’s quiescent current as if is small, but in the system will have many manostats and other functions adds will increase 10 or 20 times, this will become very big.
PSRR is the interference level gauging, once has the constant voltage, PSRR still presented on the power line. If this kind of transient state cannot suppress, then they will present in the tonal range, will become the uncomfortable tonality. Other situation will be will increase to the RF signal modulation, this will possibly cause the false transmission, but will need other filter round trip to eliminate them.
To achieve the high PSRR, LDO error amplifier in the wide frequency band usually to have the bias electric current calibration, uses under the worst working condition calibrating the maximum output electric current. Fixed and has nothing to do with along with the bias with the electric current localization, this will cause the amplifier bias and the consumption the higher quiescent current which will request compared to the low electric current definite value. Based on this reason, the high performance LDO design usually needs to have the low power dormancy pattern, reduces under the low electric current definite value the low efficiency.
Dialog the Semiconductor Corporation’s patent solves this question unique method, is uses called that it Smart Mirror the LDO manostat’s design technique, this kind of manostat compared to other manostats which uses now has the better PSRR performance.
Smart the Mirror manostat mirror image returns to the bias producer’s output current definite value, causes the bias to drop along with the definite value reduces and gives the dynamic quiescent current control automatically (to see Figure 3). This method designs the manostat has high PSRR and the dynamic property in the wide current margin, this does not possess the condition (most high loading exception) to get down the bias design compromised consideration limit. Has the automatic auto-adapted bias control, eliminated the low power working pattern which and any user intervention switch needs to the low electric current definite value low power pattern.
Uses this technology to provide 10mA LDO usually to have 99% current efficiency, consumes the electricity to be lower than 20μA. Moreover, the power source suppresses in the high band width (217Hz) has the high performance.
Smart Mirror manostat’s PSRR is bigger than 80dB, was still higher than 60dB in 10KHz its PSRR.
Very high integration rate’s PMIC besides integrates many high performance LDO, usually includes the high efficiency programmable output voltage the voltage dropping switch, may choose alone LED driver, programmable battery charger, audio frequency driver and other functions.
The voltage dropping switch improved the circuit efficiency and reduced the power loss. The belt integrates switch’s DC-DC voltage dropping switch to be possible to provide the high electric current, the low voltage power source for the baseband electric circuit, with the synchronization and the asynchronous pattern, guaranteed that in the wide electric current definite value scope the efficiency, its power source efficiency is bigger than 90%. Obviously, this regarding moves handset’s standby time and the telephone conversation time is a impact.
Model application
Portable coal body broadcast machine
Needs the power source axle along with more systems, designs needs the power source axle along with more systems, designers’ duty becomes more complex, uses the simple power source management plan to become the overall system development cycle a key aspect.
Basic PMIC suits in the low power system, if the portable media broadcast machine (see Figure 2), this kind of system includes the digit and the analogue function generally, moreover, in the system uses the advanced micro controller or DSP, thus needs to separate core nucleus and peripheral device power source. In fact basic PMIC may use in uses the single lithium battery or 3 · 3V power source’s system, for example, many computer connections (for example PCMCIA, SD, MMC, Compact Flash and mini PCI).
PMIC provides the basic system-level power source management plan, can process on/OFF control, power source ordering and the battery monitoring, enables PMIC to become the complicated system’s core. May increase other function with the standard component (for example additional manostat or battery charge), enables the designers to dispose a complete system fast.
Motion hand-hold installment
Has high integration rate PMIC to be possible (for example the Intel PXA27× processor) and the correspondence processor provides all power source management function for the motion hand-hold installment in application processor (to see Figure 4).
In the system, PMIC provides the power source, the battery management and the effective design dormancy pattern function and supports obviously saves the power wireless Intel the SpeedStep technology.
The PMIC high integration rate and the equivalent discrete component plan compares, can obviously reduce overall system’s cost and the size. Using processor control and peripheral device function related overall system, but the communication controller highlights in the wireless communication part control.
May interlock using the processor and PMIC construct a belt to attach part’s effective electrical power system few.
Majority hand-hold system request by lowest power loss work, with the aim of maintaining the long operating time. Integrates PMIC to be possible to provide several kind of working patterns: The power source interrupt, on the electricity starts, the activation and the dormancy, has the small form factor as well as the smallest PCB area
