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參數(shù)資料
| 型號： | SP6690EB |
| 英文描述： | Evaluation Board Manual |
| 中文描述： | 評估板手冊 |
| 文件頁數(shù)： | 4/16頁 |
| 文件大?。?/td> | 270K |
| 代理商： | SP6690EB |
4
Date: 05/25/04
SP6690 Micro Power Boost Regualtor, Series White LED Driver Copyright 2004 Sipex Corporation
+
-
4
Q1
Q2
R3
R4
R2
R1
X1
Shutdown
Logic
250ns
ONE-SHOT
CLEAR
X2
+
-
SET
DRIVER
52.5mV
0.15
GND
2
1
5
3
SW
POWER
TRANSISTOR
DISABLE
VIN
SHDN
FB
FUNCTIONAL DIAGRAM
THEORY OF OPERATION
General Overview:
Operation can be best understood by referring to
the functional diagram above and the typical
application circuit on the front page. Q1 and Q2
along with R3 and R4 form a band gap refer-
ence. The input to this circuit completes a feed-
back path from the high voltage output through
a voltage divider, and is used as the regulation
control input. When the voltage at the FB pin is
slightly above 1.22V, comparator X1 disables
most of the internal circuitry. Current is then
provided by capacitor C2, which slowly dis-
charges until the voltage at the FB pin drops
below the lower hysteresis point of X1, about
6mV. X1 then enables the internal circuitry,
turns on chip power, and the current in the
inductor begins to ramp up. When the current
through the driver transistor reaches about
350mA, comparator X2 clears the latch, which
turns off the driver transistor for a preset 250nS.
At the instant of shutoff, inductor current is
diverted to the output through diode D1. During
this 250nS time limit, inductor current decreases
while its energy charges C2.
At the end of the 250ns time period, driver
transistor is again allowed to turn on which
ramps the current back up to the 350mA level.
Comparator X2 clears the latch, it’s output turns
off the driver transistor, and this allows delivery
of L1’s stored kinetic energy to C2. This switch-
ing action continues until the output capacitor
voltage is charged to the point where FB is at
band gap (1.22V). When this condition is
reached, X1 turns off the internal circuitry and
the cycle repeats. The SP6690 contains circuitry
to provide protection during start-up and while
in short-circuit conditions. When FB pin volt-
age is less than approximately 300mV, the switch
off time is increased to about 1.2uS and the
current limit is reduced to about 70% of its
normal value. While in this mode, the average
inductor current is reduced and helps minimize
power dissipation in the SP6690, the external
inductor and diode.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP6690EK | Micro Power Boost Regulator Series White LED Driver |
| SP6690ER | Micro Power Boost Regulator Series White LED Driver |
| SP6690EU | Evaluation Board Manual |
| SP6690EK1 | CAP CERM .5PF 25V NP0 0201 |
| SP6691 | Micro Power Boost Regulator Series White LED Driver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP6690EK | 制造商:Exar Corporation 功能描述:Driver, Other |
| SP6690EK/TR | 制造商:Exar Corporation 功能描述:Driver, Other |
| SP6690EK1 | 制造商:Exar Corporation 功能描述:Driver, Other |
| SP6690EK1/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Micro Power Boost Regulator Series White LED Driver |
| SP6690EK-L | 制造商:Exar Corporation 功能描述:BOOST REG WHITE LED DRIVE 6690 |
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