A crucial part in this kind of system is manostat of switch of step-down type DC-DC, it can obtain inferior power supply voltage efficiently from taller voltage, if obtain the power supply voltage of 1V from 4.5 V. As manostat, its must maintain constant tension, and can make quickly to inputting the change of the change of voltage and load current answer. The article has discussion framework admirable stabilized voltage function and efficient with the good point that responds quickly.

 

Switch manostat is analysed
 

Graph 1 show the representative application circuit that gave ADI company ADP2102, this is low occupy converter of step-down of synchronous commutate of sky comparing, 3 MHz. ADP2102 has fixed output voltage and adjustable a variety of configuration that output voltage. Here joins ADP2102 fixed output voltage is configured, by the input of 5.5 V voltage produces 300mA, 0.8 V to output voltage. Give out next the applied give typical examples with output adjustable voltage.

 

Graph 1. Use ADP2102 generates 0.8 V output by 5.5 V input

 

Here explains the working principle of this circuit will simply: The component that exports DC voltage presses as referenced as the interior in error amplifier source to compare, compare the output of the output of error amplifier and voltaic sampling amplifier next, with trigger of drive only stable state. Trigger of only stable state is in stable state of of short duration inside the time cycle that decides by VOUT/VIN. Trigger of only stable state makes the door above accuses transistor to guide, the electric current in inductance L1 greatens gradually. When the stable state of of short duration of trigger of only stable state ends, transistor ends, the voltaic taper in inductance L1. In by most Xiaoguan stops time timer and the smallest (“ cereal is worth ” ) after the time-interval with affirmatory electric current, trigger of only stable state is sparked again. The only stable state inside chip sparks the make a present of before timer uses input tension, make the frequency that keeps constant when stable state.

 

The frequency that this oscillation decides with inaccuracy (it is 3MHz about) undertake continuously, but the transient state that can answer circuit and load below essential condition changes and deviate this frequency, so that output voltage to keep constant, and make the average of inductance electric current holds the voltaic cost that in output laden place needs.

 

The method that above paragraphs describes is relatively novel. Come for years, the main method that DC-DC alternates is method of electric current of constant frequency peak value, be in when this method in converter of step-down type DC-DC when implementation, its return modulation of the edge after be being called. What actor or actress to its the assessment of defect and above paragraphs are described is the detailed description that concerns this method, constant guide a converter of mode of electric current of time cereal value, ask article of referenced and other technology.

 

ADP2012 still is had owe press the closedown function, soft function that start, overheat to protect function and short circuit to protect a function, and have the feedback precision of ±1% . This framework can make advocate of switch guide a time is small to 60 Ns or lower.

 

Graph 2 show the typical weaveform that gave different condition to fall. Graph 2a is shown went out to be in ILOAD=600mA, voltage reduces VOUT=0.8V from VIN=5.5V when low occupy sky comparing. If the place in the graph is shown, below the switch frequency of 3MHz, what can obtain 45 Ns is the smallest guide a time.

 

Graph 2b is shown gave load current dash forward when adding 300mA, load current and inductance electric current are undee.

 

Graph 2c is shown gave load current dash forward when decreasing 300mA, load current and inductance electric current are undee.

 

Graph 2d is shown went out to be in occupy sky comparing to be 50% when nonexistent second harmonic oscillation, and when electric current of use peak value must be being designed when mode control, try to consider. When occupy sky comparing to be more than or be less than 50 ％ , likewise nonexistent second harmonic oscillation.

 

Graph 2a.VIN= 5.5 V, VOUT= 0.8 V, the smallest guide a time =45 Ns

 

Graph 2b. Dash forward add laden transient state to answer (ILOAD= 300 MA)

 

Graph 2c. Dash forward decrease laden transient state to answer (ILOAD= 300 MA)

 

Graph 2d. Occupy sky comparing = 50% , VIN= 3.3 V, VOUT= 1.8 V, ILOAD= 300 MA

 

The dynamic voltage in DSP application adjusts

 

In the portable application of use DSP, offer the kernel voltage of DSP and I/O voltage by switch converter normally, what this needs to use batteries power supply to apply is efficient DC-DC converter. The manostat that offers kernel voltage must the clock rate trends that can be based on processor changes voltage to perhaps change voltage according to the instruction trends of software. Additional, the small size of integral solution as much important.

 

What describe here is, in the application of batteries power supply the in-house manostat of processor of lieutenant general Blackfin® changes for exterior efficient manostat, in order to improve efficiency of systematic power supply. And, here still introduced to be used at the control software of exterior manostat.

 

Dynamic power source manages

 

The power comsumption of processor and working voltage (VCORE) square becomes direct ratio, and with working frequency (FSW) into direct ratio. Accordingly, reduce frequency to be able to make linear of dynamic power comsumption drops, and reduce kernel voltage to be able to make index of dynamic power comsumption falls.

 

In sensitive to power comsumption application, when DSP only simple monitoring system activity perhaps awaits exterior spark when signal, in maintain frequency of clock of the change below the circumstance with power supply constant tension, this is very useful to reducing power comsumption. However, in the application of high-powered batteries power supply, change frequency only and cannot remarkable and managing electric energy. Voltage of kernel of OK and ordinal change mixes Blackfin processor and the other DSP that have function of advanced report source control frequency, from this can the for love or money all realizes best batteries to use.

 

The stabilized voltage of the dynamic voltage in processor of ADSP-BF53x series Blackfin comes true by internal tension controller and exterior MOSFET normally. The advantage of this method depends on, can will odd voltage (VDDEXT) bring to bear on DSP subsystem, the needs kernel tension that gets from MOSFET (VDDINT) . It is OK to pass in-house register software controls kernel voltage, control MIPS in order to facilitate, and control specific power consumption finally, realize best battery life from this.

 

To implement plan of Blackfin interior stabilized voltage thoroughly, need diode of an exterior MOSFET, Xiao Te radical, big inductance and many output capacitor, this solution price is relatively high, efficiency is very poor however, and the PCB that take up board the area is opposite bigger, this designed personnel to bring very big contradiction to the system, in compositive manostat need uses big inductance and capacitor, the portable equipment that goes against consumer place hope as far as possible miniaturization. The efficiency of controller of this compositive stabilized voltage is relatively inferior, it is 50%~70% only normally, accordingly this method not quite apply to power supply of high-powered hand-held batteries to apply.

 

Exterior stabilized voltage

 

Devise a method through converter of new-style DC-DC switch, can improve the efficiency of itself of law of Blackfin collect set prescription 90% or taller. And, the size of exterior component can be reduced when using exterior manostat.

 

Still can use a variety of dynamic voltage to adjust (DVS) control program, include switch resistor (its can come true by DAC in certain circumstance) with wide modulation of arteries and veins (PWM) (its can realize as same as in-house method precision) . Use which kinds of program no matter, its must can change stabilized voltage n through software control. Manostat of afore-mentioned interiorly of method of stabilized voltage control are compositive, and must come true in exterior stabilized voltage through adscititious parts of an apparatus.

 

The article described synchronous DC-DC of two kinds of use ADP2102 the method of voltage of kernel of converter adjustment DSP, move below low clock speed when processor when, can go to kernel voltage dynamicly from 1.2 V adjustment 1.0V.

 

Converter of synchro switch of ADP2102 high speed is in by the batteries voltage power supply of 2.7V~5.5V when, can make kernel report depress arrives 0.8 V. Its are constant guide the voltaic mode control that tells time and 3MHz switch frequency offerred admirable trends to answer, very tall efficiency and outstanding source regulation and laden regulation. Taller switch frequency allows a system to use super- small-sized and multilayer inductance and capacitor of pottery and porcelain. ADP2102 uses 3 Mm×3 Mm LFCSP to enclose, managing space, need only 3 or 4 exterior component. And the function that ADP2102 includes to perfect, such as all sorts of safe features, if owe,press protection of closedown, short circuit and overheat protection.

 

Graph 3 show the circuit that gave implementation DVS. ADSP-BF533 EZ-KIT Lite® is evaluated board the 3.3 V power source that go up is power supply of step-down converter ADP2102, use exterior resistor voltage divider R1 and R2 are the output voltage set of ADP2102 1.2 V. The GPIO of DSP brings a foot to be used at choosing needs kernel voltage. Change feedback resistance can adjust inside the limits in 1.2 V~1.0 V kernel voltage. Pass as shunt-wound as R2 resistor R3, n channel MOSFET can revise voltage divider. Compare at R3, the RDSon of IRLML2402 is lesser, it is 0.25 Ω only. The GPIO voltage of 3.3 V is used at the grid of drive MOSFET. Better to obtain transient state performance improves laden regulation, need CFF of container of the feed before joining.

 

Graph 3. Use exterior MOSFET and Blackfin PWM control to undertake the dynamic voltage of ADP2102 is adjusted

 

To double n switch, general applied requirement is:

 

DSP kernel voltage (voltage of kernel of VOUT1) = 1.2 VDSP (= 3.3 V of voltage of input of VOUT2) = 1.0 V outputs voltaic = 300 MA

The component that uses tall block value presses resistor to be able to fall power loss to lowest. Feed contains the effect that reduces facial expression of bar leakage of electricity in switch process before. Through using lesser feedback resistor is mixed bigger before capacitance of make a present of can make be caused in this transient process rush too or next developing the smallest, but this is cost with additional power comsumption.

 

Graph 4 show gave output VOUT of voltage of voltaic IOUT, output and control voltage VSEL. When VSEL is low n, output voltage is 1.0 V, when VSEL is tall n, output voltage is 1.2 V.

 

Graph 4. Pass the feedback resistor below MOSFET adjustment

 

A kind of simpler method can create two when be used at DVS different tension, its use control voltage VC to go to voltaic infuse through another resistor in feedback network. Adjust control voltage occupy sky comparing to be able to change its average DC n. Because this uses a control,voltage and resistor can adjust output voltage. The value that the formula below uses at computational resistor R2, R3 and VC_LOW of n of control voltage extent and VC_HIGH.

 

 (1)

 

 (2)

 

To VOUT1= 1.2 V, VOUT2= 1.0 V, VFB= 0.8 V, VC_LOW= 3.3 V, VC_HIGH =0 V, with R1= 49.9 Kohm, r2andR3 can be calculated as follows

 

 (3)

 

 (4)

 

This method produced more flowing shift. Unlike MOSFET switch method, can any control voltage of drive resistor load all can be used at this plan, and the control signal source that MOSFET switch method can use at drive capacitance load only. This method can apply to any output to voltage is combined and output load current. Accordingly, adjust kernel voltage according to need, can reduce the power comsumption of DSP. Graph 5 show the shift between the two output voltage that went out to use method of infuse of this electric current.

 

Graph 5. VC of use control voltage undertakes the dynamic voltage of ADP2102 is adjusted

 

Graph 6. Through controlling the feedback resistor below voltage adjustment