XR1151
_______________________________________________________________________________________________________
1.2MHZ Step-up DC/DC Converter in SOT23-6
GENERAL DESCRIPTION
The XR1151 step-up switching regulator
generates an output voltage of up to 6V
from an input voltage as low as 1.6V. Ideal
for applications where space is limited, it
switches at 1.2MHz, allowing the use of
tiny, low cost and low profile external
components. Its internal 2A, 100mΩ
NMOS switch provides high efficiency even
at heavy load, while the constant frequency,
current mode architecture results in low,
predictable output noise that is easy to
filter. Internal frequency compensation is
designed to accommodate ceramic output
capacitors, further reducing noise. The
device features very low shutdown current
of 0.5uA.
The XR1151 is available in the 6-lead
SOT-23 package.
FEATURES
•
•
•
•
•
•
•
•
•
Internal 2A MOSFET Switch
1.2MHZ Switching Frequency
Integrated Soft-Start
Low 1.6V Vin Operation
Low
R
ds
(
on
)
Switch :100mΩ
at 5V Output
Delivers 5V at 800mA from a 3.3V input
Delivers 3V at 800mA from a 2.5V input
Uses Small.Low Profile External Components
Low profile(1mm):SOT-23(Thin SOT)package
APPLICATIONS
•
•
•
White LED Driver Supply
Local 3.3V or 5V supply
Battery Back-up
Figure 1. Typical Application Circuit
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XR1151
______________________________________ ______________________________________________________________
ORDERING INFORMATION
PART
NUMBER
XR1151
TEMP RANGE
-40°C to 85°C
SWICHING
FREQUENCY
1.2MHz
OUTPUT
VOLTAGE (V)
Adjustable
CURRENT
LIMIT(A)
2
PACKAGE
SOT23-6
PINS
6
PIN CONFIGURATION
Figure 2. PIN Configuration
PIN DESCRIPTION
PIN
NUMBER
1
2
3
4
5
6
PIN
NAME
SW
GND
FB
EN
Vin
Vin
Ground.
Feedback Input. The voltage at this pin is regulated to 0.6V. Connect to the resistor
divider between output and ground to set output voltage
Enable Input. When higher than 1.5V, this pin turns the IC on. When lower than 0.3V,
this pin turns the IC off.
PIN DESCRIPTION
Switch Output. Connect this pin to the inductor.
Power Supply
Power Supply
ABSOLUTE MAXIMUM RATINGS
(Note: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating
conditions for long periods may affect device reliability.)
PARAMETER
VALUE
UNIT
Supply Voltage VIN
-0.3 to 6.5
V
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XR1151
______________________________________ ______________________________________________________________
FB, EN Voltage
SW Voltage
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Lead Temperature (Soldering, 10 sec)
-0.3 to VIN+0.3
-0.3 to VIN+0.3
-40 to 85
125
-55 to 150
300
V
V
°C
°C
°C
°C
ELECTRICAL CHARACTERISTICS
(V
IN
= 3.6V, T
A
= 25
°
C unless otherwise specified)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Input Voltage Range
Quiescent Current
Shutdown Current
V
IN
V
FB
=0.7V EN=Vin, I
Load
=0
Iq
V
EN
=0V, V
IN
=3.3V
T
a
=25°C
1.6
65
0.5
0.588
0.6865
0.585
0.6
0.6
0.6
0.05
0.5
6.0
V
uA
0.612
0.6135
0.615
0.5
%
%
2.4
A
MHz
Ohm
1.5
0.1
1
V
µA
uA
V
Regulated Feedback
Voltage
V
FB
0< T
a
< 85°C
-40°C < T
a
<85°C
Reference Voltage Line
Regulation
Output Voltage Load
Regulation
Current Limit
Oscillator Frequency
Rds(ON) of N-channel FET
Enable Threshold
Enable Leakage Current
SW Leakage Current
I
PEAK
F
OSC
V
IN
=1.6V to 5.5V
2
V
FB
=0.6V or V
OUT
=100%
I
SW
=-100mA
V
IN
= 1.6V to 5.5V
0.3
-0.1
V
EN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V
1.2
100
1
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XR1151
______________________________________ ______________________________________________________________
Figure 3. Functional Block Diagram
FUNCTIONAL DESCRIPTION
NORMAL OPERATION
The XR1151 is a monolithic 1.2MHz boost
converter housed in a 6-lead SOT-23 package. The
device features fixed frequency, current mode PWM
control for excellent line and load regulation. The low
R
ds
(
on
)
NMOS switch enables the device to maintain
high efficiency over a wide range of load current.
Operation of the feedback loop which sets the
peak inductor current to keep the output in regulation
can be best understood by referring to the Block
Diagram in Figure 1. At the start of each clock cycle a
latch in the PWM logic is set and the NMOS switch is
turned on. The sum of a voltage proportional to the
switch current and a slope compensating voltage
ramp is fed to the positive input to the PWM
comparator. When this voltage exceeds either a
voltage proportional to the 2A current limit or the
PWM control voltage, the latch in the PWM logic is
reset and NMOS switch is turned off. The PWM
control voltage at the output of the error amplifier is
the amplified and compensated difference between
the feed- back voltage on the FB pin and the
internal reference voltage of 0.6V. If the control
voltage increases, more current is delivered to the
output. When the control voltage exceeds the ILIMIT
reference voltage, the peak current is limited to a
minimum of 2A. The current limit helps protect the
XR1151 internal switch and external components
connected to it. If the control voltage decreases,
less current is delivered to the output. During load
transients control voltage may decrease to the
point where no switching occurs until the feedback
voltage drops below the reference. The XR1151 has
an integrated soft-start feature which slowly ramps up
the feedback control node from 0V. The soft-start is
initiated when EN is pulled high.
APPLICATION INFORMATION
INDUCTOR SELECTION
The XR1151 can utilize small surface mount
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-4-
inductors due to its 1.2MHz switching frequency. A
2.2μH or 4.7μH inductor will be the best choice for
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XR1151
______________________________________ ______________________________________________________________
most XR1151 applications.
The inductor should have low DCR (DC
resistance) to reduce the I2R power losses, and
must be able to
handle the peak inductor current
without saturating.
Several inductor manufacturers are listed in Table 1
Selected inductor by actual application:
Manuf
Part
Induct DRC
acture Number ance( max
r
uH)
(Ohm
s)
Murata LQH5B
PN
LQH32P
N
Sumid
a
CDRH3
D16
2.2
2.2
2.2
4.7
0.03
3.2*2.5*1.7
0.06
0.03
0.07
4*4*1.8
Dimension
s
L*W*H(mm
3)
5*5*2
Recommended: Murata GRM32ER61A106KA01L
Murata GRM32NR61A226KE19L
OUTPUT CAPACITOR SELECTION
A low ESR output capacitor is required in order
to maintain low output voltage ripple. In the case of
ceramic output capacitors, capacitor ESR is very
small and does not contribute to the ripple, so a
lower capacitance value is acceptable when
ceramic capacitors are used. A 22uF ceramic output
capacitor is suitable for most applications.
Recommended: Murata GRM32NR61A226KE19L
OUTPUT VOLTAGE PROGRAMMING
In the adjustable version, the output voltage is
set by a resistive divider according to the following
equation:
Table 1. Recommend Surface Mount Inductors
Diode Selection
A Schottky diode is recommended for use with the
XR1151.Use of a low forward voltage diode such as
the ON Semiconductor MBRA210LT3 is
recommended. A Schottky diode rated at 2A is
recommended for use with the XR1151.
⎛
V
⎞
R
2
=
R
1
× ⎜
OUT
−
1
⎟
⎝
0.6
⎠
Typically choose R1=100K and determine R2 from
the following equation:
Connect a small capacitor across R1 feed forward
capacitance at the FB pin for better performance.
INPUT CAPACITOR SELECTION
The input capacitor reduces input voltage ripple
to the converter, low ESR ceramic capacitor is
highly recommended. For most applications, a
10~22uF capacitor is used. The input capacitor
should be placed as close as possible to VIN and
GND.
PCB Layout Guidelines
The high speed operation of the XR1151 demands
careful attention to board layout. You will not get
advertised performance with careless layout. Figure
as below shows the recommended component
placement. A large ground pin copper area will help
to lower the chip temperature.
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PCB设计
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