TK65428MTL/428 查看數據表（PDF） - Toko America Inc

零件编号

产品描述 (功能)

生产厂家

TK65428MTL/428

STEP-DOWN CONVERTER WITH BATTERY MONITOR

Toko America Inc  

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

New microprocessors are earnestly addressing this power issue by reducing the voltage. Battery manufacturers are

waking up right before the end of the century with the introduction of the “polymer electrolyte battery” which allows for higher

volumetric and gravimetric densities. Furthermore, these types of batteries come with much better form factors.

Unfortunately the wireless transmit and receive section of the portable system is very sensitive and requires very clean

analog voltages to keep a clean reception and transmission. This RF requirement reigns over the power management

section of the system and creates a dilemma to the system engineer. How do you extend the battery life with “efficient

switchers” when they are so “dirty” in performance compared to “linears”?

The industry has made attempts to get away from a sole linear system shown in Fig. 10 by considering a “PWM” switcher

in front of the linear as shown if Fig. 11.

The system of Fig. 10 has the advantage of very clean voltages for the RF section, but lacks high efficiency. Specifically

as the processor voltage drops and the battery makers refine the Li-Polimer battery (which ranges from 2.7V min to 4.2V

max).

The system of Fig. 11 has the advantage of high efficiency followed by clean RF due to the linears, but lacks the ability

to turn off (turn on) fast when the system is in standby operation. This is specifically due to the PWM architecture which

uses Continuous Conduction Mode (CCM) to build up the current in the coil.

WIRELESS PORTABLE SYSTEM USING PWM SWITCHER TO IMPROVE EFFICIENCY

Enable A

Power

Amp

Enable B

µ Controller

Enable A

Enable B

Enable C

Enable C

FIGURE 11: PWM Switcher embedded to improve wireless system efficiency

September 1999 TOKO, Inc.

Page 21

Share Link: