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SP7685EB 数据表(PDF) 4 Page - Exar Corporation

部件名 SP7685EB
功能描述  1.2A Buck/Boost Charge Pump LED Driver
PDF  13 Pages
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制造商  EXAR [Exar Corporation]
网页  http://www.exar.com
标志 EXAR - Exar Corporation

SP7685EB 数据表(HTML) 4 Page - Exar Corporation

  SP7685EB Datasheet HTML 1Page - Exar Corporation SP7685EB Datasheet HTML 2Page - Exar Corporation SP7685EB Datasheet HTML 3Page - Exar Corporation SP7685EB Datasheet HTML 4Page - Exar Corporation SP7685EB Datasheet HTML 5Page - Exar Corporation SP7685EB Datasheet HTML 6Page - Exar Corporation SP7685EB Datasheet HTML 7Page - Exar Corporation SP7685EB Datasheet HTML 8Page - Exar Corporation SP7685EB Datasheet HTML 9Page - Exar Corporation Next Button
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Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
© 2006 Sipex Corporation
FUNCTIONAL DIAGRAM
The SP7685 is a charge pump regulator
designed for converting a Li-Ion battery
voltage of 2.7V to 4.2V to drive a white LED
used in digital still camera Flash and Torch
applications. The SP7685 has two modes
of operation which are pin-selectable for
either Flash or Torch. Flash mode is usually
used with a pulse of about 200 to 300
milliseconds to generate a high intensity
Flash. Torch can be used continuously at a
lower output current than Flash and is often
used for several seconds in a digital still
camera “movie” mode.
The SP7685 also has two modes of opera-
tion to control the output current: the 1X
mode and 2X mode. Operation begins after
the enable pin EN receives a logic high, the
bandgap reference wakes up after 200μs,
and then SP7685 goes through a soft-start
mode designed to reduce inrush current.
The SP7685 starts in the 1X mode, which
THEORY OF OPERATION
acts like a linear regulator to control the
output current by continuously monitoring
the feedback pin FB. In 1X mode, if the
SP7685 auto detects a dropout condition,
which is when the FB pin is below the
regulation point for more than 32 cycles of
the internal clock, the SP7685 automati-
cally switches to the 2X mode. The SP7685
remains in the 2X mode until one of four
things happens: 1) the enable pin EN has
been toggled, 2) the Flash pin has changed
from high to low, 3) V
IN is cycled or,
4) a
thermal fault occurs.
The 2X mode is the charge pump mode
where the output can be pumped as high as
two times the input voltage, provided the
output does not exceed the maximum volt-
age for the SP7685, which is internally
limited to about 5.5V. In the 2X mode, as in
the 1X mode, the output current is regulated
by the voltage at the FB pin.
RSET BLOCK
6
RSET
RSET
RSET REF=
{
5
RSET
} x14μA
+
-
1.26V
+
-
BG REF
RSET REF
RESISTOR
TAPS
50mV
4
FLASH
FLASH=1, S=1, RSET REF
FLASH=0, S=0, 50mV
1
0 s
MUX
2x1
FB REF
7
FB
SGND 8
FB
COM P
+
-
FB COMP
CLR
COUNTER
32 COUNT
ONE
SHOT
SET
DOMINANT
S
R
0
MODE SWITCH
0 =1X
1=2X
1
5
EN
VIN
135C ON
145C OFF
THERMAL FAULT
OVER TEMP COMP
CLK
CLK
2.4MHZ
CHARGE
PUMP
SWITCHES
PGND
C1
C2
VOUT
CLK



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