DCDC电源的Tracking功能

只看该作者 · 2017-12-9 20:15

在BUCK DCDC主控IC上，很多都有一个TR/SS引脚，tracking与软启动的引脚。
软启动可以理解，tracking是什么功能。

2万 · 2017-12-10 11:53

In applications with a large amount of output capacitors, higher VOUT, or other special requirements, the soft-start
time can be extended by connecting an external capacitor CSS from SS/TRK pin to AGND. Extended soft-start
time further reduces the supply current required to charge up output capacitors and supply any output loading.
An internal current source (ISSC = 2.2 μA) charges CSS and generates a ramp from 0 V to VFB to control the
ramp-up rate of the output voltage. For a desired soft-start time tSS, the capacitance for CSS can be found by
......

http://www.ti.com.cn/cn/lit/ds/symlink/lm76003.pdf

看样子就是启动加电容

2万 · 2017-12-10 12:11

tracking应该就是跟踪的意思。
有些稳压电源，正负输出的，负输出和正输出同步跟踪的，用于特定场合，保证电源正负电压一样。
有些复杂系统，电源有多路：
电流大的数字电源，采用DC/DC电路，比如CPU的数字电源：
电流小的模拟电源，比如传感器和CPU的模拟电源；
系统要求二者电源电压一致，就是上面的跟踪这个概念。

只看该作者 · 2017-12-10 15:25

gx_huang 发表于 2017-12-10 12:11
tracking应该就是跟踪的意思。
有些稳压电源，正负输出的，负输出和正输出同步跟踪的，用于特定场合，保证 ...

LT8611，单路输出，datasheet也没有针对tracking做过多的描述。

2万 · 2017-12-10 19:58

LT8611数据手册写的很清楚，输出电压，上电时，FB不起作用，是和软启动/输出跟踪脚的电压有关。
Output Tracking and Soft-Start Pin. This
pin allows user control of output voltage ramp rate during
start-up. A TR/SS voltage below 0.97V forces the LT8611
to regulate the FB pin to equal the TR/SS pin voltage. When
TR/SS is above 0.97V, the tracking function is disabled
and the internal reference resumes control of the error
amplifier. An internal 2.2μA pull-up current from INTVCC on
this pin allows a capacitor to program output voltage slew
rate. This pin is pulled to ground with an internal 230Ω
MOSFET during shutdown and fault conditions; use a series
resistor if driving from a low impedance output. This pin
may be left floating if the tracking function is not needed.