In the design of the electronic product, the DC-DC converter is a frequently used power chip. The DC-DC converter is mainly divided into three types of boost (boost), Buck (buck), Boost-Buck (lifting down pressure), and engineers will use the corresponding circuit design.
In DC-DC selection, we need to consider numerous design indicators. For example, the most direct is the range of DC-DC converter input voltage, the working environment is 5V or 12V DC input or industry-wide 36V or 48V DC input, directly determine if the chip is appropriate; there is a more important indicator is chip The maximum load current, to estimate the power consumption according to the design of the circuit, and ensure that the DC-DC converter can provide the largest load current. Of course, the output voltage range of the DC-DC converter, efficiency, switching frequency and even the area of the circuit, etc. are all measured factors.
Today, the panel engineer recommends a DC-DC converter that is ideal for a large current working environment such as a power supply design, from the Fan2306 from the FairchildFairchild semiconductor.
FAN2306 belongs to the FAN23xx series in the Fairchild Tinybuck regulator, with high efficiency, high load characteristics, and conversion efficiency reaches 96%. The FAN2306 supports a wide voltage input range of 4.5V to 15V and can provide a continuous load current of 6A. It is precisely because the large current output makes the FAN2306 are ideal for servers, desktop computers, set-top boxes, and game consoles.
FAN23xx series regulator
This love board engineer gets not only Fan2306 synchronous bucklers, but also the power evaluation board FebFan2306_lva based on this buck product.
FAN2306 DC-DC buckler
Synchronous buckler FAN2306 system principle block diagram
FAN2306 is an efficient integrated TinyBuckTM synchronous buck regulator with the following features:
Voltage input range 4.5V ~ 15V, voltage output range 0.6V ~ 5.5V
More than 96% efficiency, sustainable load current of up to 6A
The on-resistance RDS of the anti-pulder MOSFET is only 5.46 ~ 9.67MΩ
Support light load PFM mode, ultrasound mode, low cut-off current, thermal shuttle function
Adjustable frequency range: 200kHz ~ 1.5MHz, adjustable soft start time
Generally speaking, the efficiency of the switching power supply and high load, while the load is lowered to a certain valve value. The high efficiency of FAN2306 is not only to say its maximum efficiency of more than 96%, but there is also a very high conversion efficiency in the case of light load (the specific energy efficiency of the FAN2306 synchronous buck can be refer to the figure below). For example, the left side below can see if the output 5V is in high load (output current 2a), the conversion efficiency is over 95% or more; until the light load condition (tens of MA level) conversion efficiency is maintained for more than 90%.
FAN2306 efficiency in different states
The FAN2306 is mainly to reduce the efficiency of low load when the switching frequency can be reduced by pulse frequency modulation (PFM) mode under light load conditions. In addition, the FAN2306 also has an ultrasound mode that holds the switching frequency over the audible range by minimum frequency clamping.
Fan2306 has some other features, for example it is a synchronous buckler, we know that synchronization is more efficient than asynchronous buck compared to asynchronous bucklers. The output of the buffer uses MOSFET instead of an asynchronous rectifier diode, which refers to the MOSFET of the output terminal to maintain a certain phase relationship, which is called synchronous buck. This is not only efficient, and the on-resistance is smaller.
There is also an adjustable adjustable, such as the fan2306 supports soft boot, change the size of the switching frequency and the on-time of the switching frequency, and the soft start pin SS (Soft-start) changes the DCDC soft start by changing the size of the external capacitance value. Time, it can prevent the surge of the current from the surge and overshoot damage to the output voltage.
Overall, FAN2306 can provide high load currents of up to 6A, more than 96% efficiency, is a high efficiency, high-load DC-DC converter. At the same time, it has most common functions of synchronous buck DC-DC.
Power evaluation board Febfan2306_lva
After saying, FAN2306 synchronous Tinybuck regulator, let's take a power evaluation board FebFan2306_lva, the power evaluation board size is 7cm * 7cm, 4-layer PCB board process, front, and the back side two parts can just divide the entire power assessment board into two Some functional circuits:
Power evaluation board Febfan2306_lva
The positive PCB is mainly based on the 1.2V output circuit design of the FAN2306 buck chip. The switching frequency is 500kHz. Here, it will be explained, although this buck chip can output an output voltage range of 0.6V to 5.5V and a switching frequency of 200 ~ 1500kHz. Range, but in the FebFan2306_LVA power evaluation board, 1.2V voltage regulatory output and 500 kHz fixed switching frequency, we can also see from above, FAN2306 antihypertensive has a very small package size (5.5mm * 5mm) Even in the design of the entire circuit, there is no size of a inductor.
The back surface of the PCB is mainly transient generator circuit, which is used to test the state in which the FAN2306 buck chip is in very rapid transient load environments. The transient generator circuit is mainly through the LM555 timer, the adjustable resistor, the gate driver FAN3226T and Two MOSFET FDMS7658AS for output, the adjustable resistor is used to adjust the frequency and duty cycle of the timer to adjust the load output state of the transient circuit.
The addition of the transient generator circuit can affect the efficiency test of the evaluation board for the buck chip FAN2306, so there is a hop on the front of the FebFan2306_lva power evaluation board to set whether the evaluation board is to be added to the transient generator circuit load, when you only want to test When Fan2306 buck chip is efficient, disconnecting transient generator circuit jumps is not bilateral choice.
The top needle distribution on the evaluation board is the necessary signal foot for the normal operation of the FAN2306 buck, such as enable pin signal, bias voltage input signal, which will be used in the actual experience below.
Introduction to the basic theoretical knowledge of the Febfan2306_LVA power assessment board and the FAN2306 antihypertensive, and then look at how the board is actually powerful. The panel engineer has done some power-on preparations based on the resources available for hand:
A digital power supply as an evaluation board FebFan2306_lva 4.5V ~ 15V power supply input
A 10V bias power supply for 5V and 3.3V voltages can be provided as a power supply evaluation board FebFan2306_lva, and 3.3V enable power
A two-channel oscilloscope test evaluation board enables the relationship between the signal and the output voltage signal
To observe the highest efficiency of the FAN2306 buck chip, before evaluating the board, you can remove the pavilion of the onboard transient generator (removing the transient generator circuit), and the post-power test, the observed waveform is as follows Shown in the figure
Schematic diagram of enabling foot and output voltage waveform
Blue is a 3.3V enable voltage input waveform, and the yellow waveform is a 1.2V output voltage at the time of no load. In this test, we provide 5V bias voltages and 3.3V enable voltages for the power evaluation board, respectively. Also, the normal operation of the FAN2306 buckler can be implemented by pulling the enable pin to the VCC pin.
In fact, the Febfan2306_LVA evaluation board reserved the test station solder joint (such as VSW, Vout) in several positions, some unfortunately these original devices did not patch, no way, in these test points When testing, you have to manually operate, as shown below, and the panel engineer tests open the correction wave VSW in an air-up condition.
Test no-load case vsw
Timer adjustment in transient load circuit
Closing the transient load trip of the power evaluation board, at which time the timer has been working, you can view the frequency and duty cycle of the timer output through the timer frequency test point, see the figure below.
Test timer output frequency
The output frequency of the two resistors in the back of the FEBFAN2306_LVA evaluates the output frequency of the board, and the following figure is the waveform when the 500kHz frequency output is adjusted.
Adjust the frequency of the timer
Why adjust the timer output frequency? The fundamental purpose is to adjust the load change of the transient generator. However, the transient circuit ultimately forms the output and the most critical step, can you think of? This allows the panel engineer to sell a little clearance first, which will be announced in a later evaluation article.
summary
This article mainly introduces Fairchild Semiconductor Power Evaluation Board FebFan2306_LVA and the basic hardware resources of the FAN2306 Tinybuck regulator and the first-time power-up trial of board cards. It is not difficult to see that the FAN2306 antihypertensive is high efficiency, high load characteristics are extremely strong in the terminal market. Competitiveness. This article only uses the oscilloscope to simply test the signal output waveform of the power supply evaluation board, familiar with the method of use of the power supply evaluation board, and in the next evaluation, the online engineers will be fully loaded (6a) through the instrument of the electronic load and other instruments (6A) and the instantaneous Signal output status in the case of load, so stay tuned!
Reference
FAIRCHILD Semiconductor FAN2306 Synchronous Buckle Data
Febfan2306_lva Power Evaluation Board Information
Fairchild semiconductor online power supply design tool
Original declaration: This article is originally created by the panel network, declined!
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