參數(shù)資料
型號(hào)： TPS40051QPWPRQ1
廠商： TEXAS INSTRUMENTS INC
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
封裝： PLASTIC, HTSSOP-16
文件頁(yè)數(shù)： 3/35頁(yè)
文件大?。?/td> 498K
代理商： TPS40051QPWPRQ1
TPS40050Q1
TPS40051Q1
TPS40053Q1
SGLS219A NOVEMBER 2003 REVISED MAY 2008
www.ti.com
11
APPLICATION INFORMATION
Once the soft-start is initiated, the UVLO cicruit must see a total count of seven cycles in which the ramp duration
is longer than the clock cycle before an undervoltage condition is declared. (See Figure 4).
UDG02132
Clock
PWM RAMP
PowerGood
VIN
UVLO Threshold
1 2 3 4 5 6 7
1 2
Figure 4. Undervoltage Lockout Operation
Some applications may require an additional circuit to prevent false restarts at the UVLO voltage level. This
applies to applications which have high impedance on the input voltage line or which have excessive ringing
on the VIN line. The input voltage impedance can cause the input voltage to sag enough at start-up to cause
a UVLO shutdown and subsequent restart. Excessive ringing can also affect the voltage seen by the device
and cause a UVLO shutdown and restart. A simple external circuit provides a selectable amount of hysteresis
to prevent the nuisance UVLO shutdown.
Assuming a hysteresis current of 10% IKFF, and the peak detector charges to 8 V and VIN(min) = 18 V, the value
of RA is calculated by:
R
A +
R
KFF
(8
* 3.5)
0.1
V
IN(min) * 3.5
+ 565 kW ^ 562 kW
CA is chosen to maintain the peak voltage between switching cycles. To keep the capacitor charge from
drooping 0.1-V, or from 8 V to 7.9 V.
C
A +
(8
* 3.5)
R
A
7.9
f
SW
The value of CA imay calculate to less than 10 pF, but some standard value up to 470 pF works adequately.
The diode can be a small signal switching diode or Schottky rated for more then 20 V. Figure 5 illustrates a typical
implementation using a small switching diode.
The tolerance on the UVLO set point also affects the maximum duty cycle achievable. If the UVLO starts the
device at 10% below the nominal start up voltage, the maximum duty cycle is reduced approximately 10% at
the nominal start up voltage.
(4)
(5)
相關(guān)PDF資料
PDF描述
TPS40051PWP 0.2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
TPS40050PWP 0.2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
TPS40050PWPG4 0.2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
TPS40051PWPR 0.2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
TPS40053PWPG4 0.2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
相關(guān)代理商/技術(shù)參數(shù)
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TPS40052PWPR 功能描述:DC/DC 開(kāi)關(guān)控制器 Wide Input Sync Buck Cntrlr w/DDR trking RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
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