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Construction of Mobile Internet Devices Power Analysis

In Electronic Infomation Category: C | on April 13,2011

Mobile Internet Device (MID) is a kind of electronic mobile devices, enabling customers to carry their "mobile world." It provides high-quality portable video device and LXT908LE datasheet and full page Web browsing experience, so that users can take full advantage of mobile broadband to get the optimized Web browsing experience.

MID system block diagram is shown below.


system block diagram of Figure 1 MID

The entire program to CPU core, with peripheral devices such as audio and LXT908LE price and video and LXT908LE suppliers and storage, together constitute the MID system. Of its parts correspond to the power system as shown below:


Figure 2 MID corresponding to various parts of the systems power supply system

The entire power system starting from the AC-DC adapters, application:

A charge management unit (6.6-8.4V1A, two lithium batteries),

B RTC (with 3.3V LDO output voltage),

C USB & DVI unit (12V/9V to 5V, can be used to achieve high-voltage synchronous buck DC-chip),

D LCD module (5V step-up to achieve 10-15V),

E CPU (5V Synchronous Buck to 3.3V),

F Bluetooth and storage units (5V Synchronous Buck realized),

G Audio & Video Codec Unit (5V LDO achieved by)

See from the power system, AC-DC, after the output, 12V 5V switch the interface of the entire power system of the most important part, a direct impact on its stability and efficiency of multiple units behind it. It should be high voltage (considering margin, voltage 15V or more appropriate), can be too large current (1.5A or more) and high-efficiency power supply solutions. Microelectronics Co., Ltd. Wuxi core friends

for this application, launched a high-voltage DC-DC buck chip AP2952.

AP2952 is a monolithic synchronous buck regulator rectifier, which integrates on-resistance 130m? The MOSFET, can be very wide input voltage range (4.75V-18V) to provide the load capacity of 2A. Current mode control to make it a good transient response and single-cycle current limiting. Adjustable soft-start time to avoid the opening moments of the impact of current, in the standby mode, the input current is less than 1uA.

AP2952 and packaged as SOP8 SOP8-PP, while providing a compact system solution that can minimize external components.

Key features

2A output current

input voltage range of 4.75 to 18V

130m within the integrated power MOSFET

output tuning range of 0.925V to 15V

efficiency up to 95%

Adjustable soft start time

the external use of low ESR ceramic capacitors can guarantee its stability

a fixed 450kHz frequency

Each cycle is limited streaming capabilities

has under-voltage protection function

cooling capacity and strong SOP8 SOP8-PP package

Internal block diagram of the


internal block diagram of Figure 3

12V 5V transfer program (using the AP2952 power management chip)


Figure 4 12V 5V transfer program (using the AP2952 power management chip)

1) FB-side resistance


Where Vfb = 0.925V (built-EA), Vout = 5.0V, take R2 = 10K (recommended typical value), calculated by the above formula R1 = 44.2K.

2) SW end of the inductor L1 of the value


Where fs = 450KHz, Vout = 5V, Vin = 12V,

IL = IL * r, r for the current ripple ratio, taking r = 0.4 (reference to the U.S. Sanjaya Maniktala compiled the "master switch power" (Peoples Posts and Telecommunications Press) p. 52 "rs Best Value" section), the

IL = IL * r = 1.5A * 0.4 = 0.6A

Substituted into the formula L can be L = 10.8uH, take L to 10uH.

3) Comp feet R3 C3 values, recommended the RC circuit 6.8K and 3.9nF compensation

4) GND chip to side

5) BS side (High-side Gate Boost input), 0.01uF capacitor connected to the SW side

6) Input voltage 12V directly to the IN side, then 100K resistors connected to the EN terminal.

Test the efficiency of the curve as shown, 12V Input 5V 1.5A when the output efficiency of up to 90%.


Figure 5, the efficiency of the test graph

Addition to MID application, AP2952 for DVB, Notebook, and DSP power supply high voltage DC-DC converter circuit. AP2952 almost started batch applications, superior performance and unique high-pressure technology for high-voltage DC-DC is committed to power management engineers to provide a new choice.

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