MP1522(2003) 데이터 시트보기 (PDF) - Monolithic Power Systems
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MP1522 Datasheet PDF : 8 Pages
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Monolithic Power Systems
MP1522
25V Step Up Converter
in 3mm QFN Package
Figure 2: Functional Block Diagram
VIN
ON/OFF
C1
R3
EN
(6)
C2
BIAS (4)
REGULATOR
INTERNAL
POWER
CONTROL
LOGIC
CURRENT
D1
L1
VOUT
R2
C3
C4
SW
(3)
GND
380mA
MP152
ERROR AMP.
FB
(1)
R1
+
1.235V -
GND (2,5)
Functional Description
The MP1522 is a step-up converter that
operates from an input voltage as low as 2.7V
and generates an output voltage up to 25V. The
0.5Ω internal n-channel MOSFET power switch
is driven with a variable frequency,.constant-
peak-current architecture for improved
regulation and low operating current. The 500ns
minimum off-time is extended to 1.8µs during
start-up to yield a smooth glitch free turn-on.
Start-up mode is activated at initial power-up or
when exiting the 1µA shutdown state. The
MP1522 features an internal regulator allowing
it to be powered from the output for improved
low-input voltage operation, or powered from
the input source for reduced quiescent current.
Variable Frequency
Constant-Peak-Current Operation
When the power MOSFET is turned on the
inductor current increases until the 0.5A current
limit is reached. The Power MOSFET is then
turned off for a minimum of 500ns. At the end of
this 500ns transition if the feedback pin is still
lower than the 1.235V internal reference the
power MOSFET will again be turned on,
otherwise the MP1522 waits until the voltage
drops below the threshold before turning on the
MOSFET again. This process allows for optimal
use of the inductor, while minimizing the output
ripple and size of the output capacitor and
maintaining low operating current.
MP1522 Rev 1.7_06/26/03
Monolithic Power Systems, Inc.
4
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