MP1522
25V Step-Up Converter
in a SOT23-5 Package
The Future of Analog IC Technology
DESCRIPTION
The MP1522 is a step up converter that
generates up to a 25V output voltage from a
2.7V to 25V input. It uses a current limited
Variable Frequency control algorithm to
optimize efficiency and minimize external
component size and cost. The internal 0.5Ω
N-Channel MOSFET switch can withstand up to
28V allowing the MP1522 to produce high
output voltage with high efficiency.
The MP1522 includes input under voltage and
over temperature protection. The MP1522 is
available in tiny 5-pin SOT23 and 3x3 QFN6
packages.
FEATURES
•
•
•
•
•
•
•
•
Internal 0.5Ω Power Switch
Output Voltage up to 25V
Up to 90% Efficiency
Low 1µA Shutdown Current
Input Under Voltage Protection
Thermal Shutdown
Internal Current Limit
Available in Tiny 5-Pin SOT23 and 6-Pin
3x3 QFN Packages
Handheld Computers, PDAs
Cell Phones
Digital Still and Video Cameras
Small LCD Displays
APPLICATIONS
•
•
•
•
EVALUATION BOARD REFERENCE
Board Number
EV0022
Dimensions
2.2”X x 1.5”Y x 0.5”Z
“MPS” and “The Future of Analog IC Technology” are Registered
Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
V
IN
3.3V
100
90
Efficiency vs Load Current
with BIAS Tied to V
OUT
10V
5.0V
3.3V
OFF ON
4
EN
SW
1
5
3
V
OUT
20V
C2
1nF
EFFICIENCY (%)
D1
RB751
80
70
60
MP1522
2
GND
BIAS
FB
V
OUT
= 12V
50
1
MP1522_TAC_S01
10
100
1000
MP1522_TAC_EC01
LOAD CURRENT (mA)
MP1522 Rev. 1.9
12/9/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
1
MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
PACKAGE REFERENCE
TOP VIEW
SW
GND
FB
1
5
BIAS
ABSOLUTE MAXIMUM RATINGS
(1)
BIAS .............................................. –0.3V to 28V
SW ................................................. –0.5V to 28V
All Other Pins................................... –0.3V to 6V
Junction Temperature...............................150°C
Solder Temperature..................................260°C
Storage Temperature ................–65°C to 150°C
MARKING
4
EN
MP1522_PD01-TSOT23-5
2
3
Recommended Operating Conditions
(2)
BIAS Supply Voltage ....................... 2.7V to 25V
Output Voltage....................................V
IN
to 25V
Operating Temperature .............–20°C to +85°C
Thermal Resistance
(3)
Part Number*
MP1522ET
MP1522EQ
*
Package
SOT23-5
3x3 QFN6
Temperature
–20°C to +85°C
–20°C to +85°C
SOT23-5 ................................ 220 .... 110..
°C/W
3x3 QFN6 ............................... 50 ...... 14...
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
θ
JA
θ
JC
For Tape & Reel, add suffix –Z (eg. MP1522ET–Z)
For Lead Free, add suffix –LF (eg. MP1522ET–LF–Z)
ELECTRICAL CHARACTERISTICS
V
BIAS
= V
EN
= 5.0V, T
A
= +25°C, unless otherwise noted.
Parameter
Symbol Condition
Supply Current (Shutdown)
I
BIAS (OFF)
V
EN
= 0V
Supply Current (Quiescent)
I
BIAS(ON)
V
FB
= 1.3V
Min Off Time, Normal
T
OFF
V
FB
= 1.23V
Operation
Min Off Time, Start-Up
(4)
T
OFF
V
FB
= 0V
Undervoltage Lockout
BIAS Under Voltage Lockout UVLO V
BIAS
Rising,
100mV Hysteresis (Typical)
Enable
EN Threshold
V
EN
Rising
EN Hysteresis
EN Input Bias Current
V
EN
= 0V, 5V
Feedback Comparator
FB Regulation Threshold
V
FB
Falling
(5)
FB Hysteresis
FB Input Bias Current
V
FB
= 1.23V
Output Switch
SW On-Resistance
(5)
R
ON
V
BIAS
= 5.0V
SW Current Limit
SW Leakage Current
V
SW
=25V
(5)
Thermal Shutdown
Notes:
4) First 64 pulses after EN switches High
5) Guaranteed by design.
Min
300
Typ
1
650
550
1.6
Max
3
750
700
Units
µA
µA
ns
µs
2.1
2.3
2.65
V
0.8
1.1
60
2.0
1
V
mV
µA
V
mV
nA
Ω
mA
µA
°C
1.19
–150
1.23
10
–80
0.5
450
160
1.27
0.6
10
300
MP1522 Rev. 1.9
12/9/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
2
MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
PIN FUNCTIONS
Pin #
1
2
3
4
Name
SW
GND
FB
EN
Description
Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power
inductor and output rectifier to SW. SW can swing between GND and 25V.
Ground.
Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set
the output voltage. The feedback regulation threshold is 1.23V.
Regulator On/Off Control Input. A high voltage at EN turns on the converter, and a low
voltage turns it off. When not used, connect EN to the input source for automatic startup. If
EN is driven over 6V, place a 100kΩ resistor in series with EN.
Internal Power Input. BIAS powers the internal circuitry. Connect BIAS to the output for
more enhancement on the internal MOSFET gate at low V
IN
. If the input source remains
above 3.0V, BIAS can be connected to the input source to reduce power consumption.
5
BIAS
OPERATION
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 550ns
minimum off-time is extended to 1.6µs 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 power
consumption due to quiescent current.
L1
V
IN
BIAS
(5)
D1
V
OUT
SW
(1)
C4
C1
R3
EN
(4)
R2
C2
C3
REGULATOR
INTERNAL
POWER
GND
OFF ON
CONTROL
LOGIC
CURRENT
--
+
450mA
FB
(3)
ERROR
AMP --
+
1.23V
GND
(2)
R1
MP1522_BD01
Figure 1—Functional Block Diagram
MP1522 Rev. 1.9
12/9/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
3
MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
Variable Frequency
Constant-Peak-Current Operation
When the power MOSFET is turned on the
inductor current increases until the 0.45A
current limit is reached. The Power MOSFET is
then turned off for a minimum of 550ns. At the
end of this 550ns transition if the feedback pin
is still lower than the 1.23V 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.
Setting the Output Voltage
The output voltage is set by a resistive voltage
divider connecting the output voltage to FB. The
voltage divider reduces the output voltage down
by the ratio:
V
OUT
R1
+
R2
=
V
FB
R1
On/Off Control
The EN input is used to turn the converter on
and off. A high input at EN turns the converter
on and a low level turns the converter off. When
EN is not being used, connect to the input
source for automatic startup. For inputs greater
than 6V, pull EN to V
IN
through a 100kΩ
resistor.
Input Capacitor
To reduce noise, use a low ESR/ESL type input
capacitor. A 1µF surface mount ceramic
capacitor close to the input supply side of the
inductor minimizes EMI and ripple current at the
input source. See the section on printed circuit
board layout for reducing noise and emissions.
A bypass capacitor is typically required to
prevent noise at the MP1522. This capacitor
should also be a low ESR/ESL type capacitor.
Place a 0.1µF surface mount ceramic capacitor
between BIAS and GND as close to the
MP1522 as possible.
Output Capacitor
To minimize output voltage ripple and noise use
a low ESR/ESL type output capacitor. Typically
a 1µF surface mount ceramic capacitor is
sufficient. When using aluminum electrolytics,
tantalum or aluminum polymer capacitors the
ESR/ESL dominate the output ripple. See the
section on printed circuit board layout.
Inductor
The inductor stores energy during the power
MOSFET switch on-time. This energy is
transferred to the output during the switch off-
time. Select an inductor whose peak-current
rating is greater than the 450mA peak current
limit of the MP1522. Lower value inductors yield
higher switching frequencies and thus lower
output ripple voltage. However, using too low a
value inductor will cause an increase in peak
current limit due to the delay of the current-limit
comparator. Choose an inductor such that the
peak current limit is reached in 550ns or longer.
The minimum value inductor for this criterion is:
L
≥
1.31
×
10
−
6
×
V
IN
(
µ
H
)
Solving for V
OUT
⎛
R1
+
R2
⎞
V
OUT
=
V
FB
⎜
⎟
⎝
R1
⎠
Where V
OUT
is the output voltage, and V
FB
is the
1.23V feedback threshold. Substituting the
feedback threshold voltage:
⎛
R1
+
R2
⎞
V
OUT
=
1.23 V
⎜
⎟
⎝
R1
⎠
R1 can range from 10kΩ to 200kΩ. R2 is
determined the equation:
⎡⎛
V
R2
=
R1
⎢⎜
OUT
⎜
⎢⎝
V
FB
⎣
⎞ ⎤
⎟ −
1
⎥
⎟
⎠ ⎥
⎦
For example for an output voltage of 20V and
R1 = 130kΩ the formula yields:
⎡⎛
20
⎞ ⎤
R2
=
130k
Ω ⎢⎜
⎟ −
1
⎥
⎣⎝
1.23 V
⎠ ⎦
R2 = 2MΩ the closest standard 1% resistor
value.
The feedback divider requires a feed-forward
capacitor connected in parallel with R2. This
capacitor is typically in the range of 1nF-10nF.
MP1522 Rev. 1.9
12/9/2005
For maximum V
IN
= 3.3V, use an inductor value
greater than 4.7µH, and for maximum V
IN
= 5V
use an inductor value greater than 6.8µH.
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
4
MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE
Diode
The high switching frequencies of the MP1522
require the use of fast recovery or Schottky
barrier diodes. In low voltage applications
Schottky barrier diodes are recommended for
maximum efficiency. The reverse breakdown
voltage should be approximately 1.5X the
output voltage.
Printed Circuit Board Layout
The printed circuit board layout is important in
order to minimize noise and prevent erratic
operation. Keep the ground leads short and
robust with minimum lead lengths between the
input and output capacitors and ground. Place
the feedback resistive voltage divider as close
to FB as possible to prevent switching noise
injection into FB. The use of surface mount
capacitors with their low ESL is required to
minimize noise at the MP1522. Use separate
power and quiet ground planes connected
together at a single point whenever possible to
minimize.ground.bounce.
Table 1—Output Current vs. Input Voltage
V
IN
(V)
3.3
3.3
3.3
3.3
5
5
5
10
10
10
V
OUT
(V)
5
12
18
25
12
18
25
12
18
25
I
OUT
(mA)
67
28
15
10
44
32
19
122
75
51
V
IN
3.3V
OFF ON
4
EN
SW
1
5
3
D1
RB751
C2
1nF
V
OUT
20V
MP1522
2
GND
BIAS
FB
MP1522_TAC_F02
Figure 2—Typical Boost Application
MP1522 Rev. 1.9
12/9/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
5
/2017104796055_pdf/pg_0001.png)
京公网安备 11010802033920号
EEWORLD/2017104796055_pdf/1.png)
/2017104796055_pdf/2.png)
/2017104796055_pdf/3.png)
/2017104796055_pdf/4.png)
/2017104796055_pdf/5.png)
/2017104796055_pdf/pg_0002.png)
/2017104796055_pdf/pg_0003.png)
/2017104796055_pdf/pg_0004.png)
/2017104796055_pdf/pg_0005.png)
