參數(shù)資料
型號: PTB78560AAZ
廠商: TEXAS INSTRUMENTS INC
元件分類: 電源模塊
英文描述: 1-OUTPUT 30 W DC-DC REG PWR SUPPLY MODULE
封裝: ROHS COMPLIANT, DIP11
文件頁數(shù): 9/27頁
文件大小: 643K
代理商: PTB78560AAZ
www.ti.com
Sequenced Power Up with POL Modules
Overview
Auto-Track Features
SLTS249 – JUNE 2005
The main output from the PTB78560x converters is VOBus. In power sequencing applications, VOBus is used as
the intermediate supply voltage for powering one or more downstream nonisolated power modules that
incorporate Auto-Track1. The output voltage from Auto-Track compliant modules can be sequenced using a
control input called Track. The Track input directly controls the output of a module from zero to its set-point
voltage. The control is on a volt-for-volt basis, and allows multiple modules to follow a common analog signal
during power-up events.
The Track signal attempts to start rising when the nonisolated modules are first powered from VOBus. However,
for proper sequencing, the voltage must be held at ground potential for at least 20 ms (40 ms for 12-V input
modules) after VOBus is in regulation. This is necessary to allow time for the nonisolated modules to complete
their power-up initialization. The Track pin of each PTB78560x converter has an internal open-drain transistor
that automatically holds the Track signal at ground potential to comply with this requirement.
The PTB78560B (1.8 V to 3.6 V) has a VOSeq output. VOSeq is internally derived from VOBus and regulated to
the same set-point voltage. It has the added feature of being controlled by the Track input. During power up, this
output can sequence with the outputs of the nonisolated modules powered from VOBus.
Figure 26 shows a block diagram of the converter Auto-Track features. The components shaded are only
present in the PTB78560B. During power up, VOBus rises promptly, after the converter is connected to a valid
input source and its output is enabled. VOSeq (PTB78560B) is the Auto-Track compatible output that is
controlled by the voltage presented at the Track terminal. The control is active from 0 V up to a voltage just
below the VOBus output. Between these limits, the voltage at VOSeq follows that at the Track terminal. Once the
Track voltage is at the VOBus voltage, raising it higher has no further effect. The voltage at VOSeq cannot go
higher than VOBus, and if connected to +Sense, it regulates at the set-point voltage.
2
The Track input to the PTB78560x series of converters include a pullup resistor (RTRK) to VOBus, and a 1-F
capacitor (CTRK) to -Sense. These components are standard on all Auto-Track compatible modules. They form
an R–C time constant that cause the Track voltage to rise when the internal MOSFET is turned off. The
unity-gain relationship between VOSeq and the Track input is the same as all other Auto-Track compliant
outputs.3 The VOSeq output also follows a compatible external ramp waveform applied to the Track pin.
4, 5 The
internal MOSFET is designed to hold the Track voltage at ground potential for the required period after the
VOBus output is in regulation.
17
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相關代理商/技術參數(shù)
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