參數(shù)資料
型號: TPS40101RGET
廠商: TEXAS INSTRUMENTS INC
元件分類: 穩(wěn)壓器
英文描述: 1.3 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC24
封裝: PLASTIC, QFN-24
文件頁數(shù): 21/37頁
文件大?。?/td> 774K
代理商: TPS40101RGET
www.ti.com
Pre-Bias Operation
Remote Sense
SLUS726 – SEPTEMBER 2006
Some applications require that the converter not sink current during startup if a pre-existing voltage exists at the
output. Since synchronous buck converters inherently sink current some method of overcoming this
characteristic must be employed. Applications that require this operation are typically power rails for a multiple
supply processor or ASIC. The method used in this controller, is to not allow the low side or rectifier FET to turn
on until the output voltage commanded by the start up ramp is higher than the pre-existing output voltage. This
is detected by monitoring the internal pulse width modulator (PWM) for its first output pulse. Since this controller
uses a closed loop startup, the first output pulse from the PWM does not occur until the output voltage is
commanded to be higher than the pre-existing voltage. This effectively limits the controller to sourcing current
only during the startup sequence. If the pre-existing voltage is higher that the intended regulation point for the
output of the converter, the converter starts and sinks current when the soft-start time has completed.
The TPS 40100 is capable of remotely sensing the load voltage to improve load regulation. This is accomplished
by connecting the GND pin of the device and the feedback voltage divider as near to the load as possible.
CAUTION:
Trace Length Considerations
More than a few inches of trace length between the GND pin of the device and the load GND can lead to
significantly increased pulse width jitter. As a starting point, the GND pin connection should be no further than
six inches from the PGND connection. The actual distance that starts causing erratic behavior is application and
layout dependent and must be evaluated on an individual basis. If the controller exhibits output pulse jitter in
excess of 25 ns and the GND pin is tied to the load ground, connecting the GND pin closer to the PGND pin
(and thereby sacrificing some load regulation) may improve performance. In either case, connecting the
feedback voltage divider at the point of load should not cause any problems. For layout, the voltage divider
components should be close to the device and a trace can be run from there to the load point.
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相關代理商/技術參數(shù)
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