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Электронный компонент: FAN4855MU

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www.fairchildsemi.com
REV. 1.0.0 3/17/04
Features
Low power PFM boost regulator
Input voltage range is from 1.6V to 4.5V
Output voltage range is from 3V to 5V
500mA maximum load current capability
95% efficient power conversion
2-3 cell and single cell Li-Ion systems
Variable on-time Pulse Frequency Modulation (PFM)
Internal synchronous rectifier (no need for external diode)
Low-battery detection
Logic controlled shutdown with true-load disconnect
Low (80A) quiescent current
MSOP-8 and TSSOP-8 Packages
Applications
DSCs
PDAs
Cell phones, smart phones
Portable instrumentations
2-3 AA / AAA cells operated devices
Single cell Li-Ion operated devices
General Description
The FAN4855 is a low power boost regulator designed for
low voltage DC to DC conversion in 2-cell battery powered
systems such as digital cameras, cell phones and PDAs.
The converter starts-up at 1.3V and operates after the start at
an input voltage as low as 1V. Output voltage can be adjusted
by external resistors from 3.3V to 5V with a maximum load
current of 0.5A. Quiescent current in shut-down mode is
less than 10A, which maximizes the battery live time. The
ON time changes with the input voltage to maintain the
ripple current constant and to provide the highest efficiency
over a wide load range--while maintaining low peak
currents in the boost inductor. The combination of built-in
power transistors, synchronous rectification and low supply
current, make the FAN4855 ideal for portable applications.
The FAN4855 is available in 8-lead MSOP and TSSOP
packages.
FAN4855
500mA High Efficiency Boost Regulator with
Adjustable Output, Shutdown and Low Battery Detect
Typical Application
V
IN
Input 1.6V
to 4.5V
On
Off
Low Battery
Detect In
Output 3.3V to 5V
up to 0.5A
FAN4855
Low Battery
Detect Out
SHDN
LBI
LB0
GND
V
L
V
OUT
FB
1
2
3
4
8
7
6
5
PRODUCT SPECIFICATION
FAN4855
2
REV. 1.0.0 3/17/04
Pin Configuration
Pin Description
Absolute Maximum Ratings
Absolute Maximum Ratings are those values, beyond which the device could be permanently damaged. Absolute maximum
ratings are stress ratings only and functional device operation is not implied.
PIN
NAME
FUNCTION
1
V
IN
Battery Input Voltage
. Supplies the IC during start-up. After the output is running, the IC draws
power from V
OUT
.
2
SHDN
Shut Down
. Pulling this pin low shuts down the regulator, isolating the load from the input.
3
LBI
Low-Battery Input
. Pulling this pin below 0.39V causes the LBO pin to go low.
4
LBO
Low-Battery Output
. This pin provides an active low signal to alert the user when the LBI
voltage falls below its targeted value. The open-drain output can be used to reset a
microcontroller.
5
FB
Feedback Input
. For setting the output voltage. Connect this pin to the resistor divider.
6
V
OUT
Boost regulator output
. Output voltage can be set to be in the 3 to 5V range. Startup at
moderate load is achievable at input voltages around 1.35V.
7
V
L
Boost inductor connection
. Connect an inductor between this pin and V
IN
. When servicing the
output supply, this pin pulls low, charging the inductor, then shuts off dumping the energy through
the synchronous rectifier to the output.
8
GND
Ground of the IC
.
Parameter Min.
Max.
Units
V
IN
,
V
OUT
Voltages (Relative to GND)
-0.3
6.5
V
Switch Voltage (V
L
to GND)
-0.3
V
OUT
+ 0.3
V
Voltage on any other Pin
-0.3
V
OUT
+ 0.3
V
Peak Switch Current (Ipeak)
-- Internally Limited --
Output Current (I
OUT
)
500
mA
Continuous Power Dissipation
TSSOP Package
525
mW
MSOP Package
315
Thermal Resistance (
JA
)
TSSOP Package
124
C/W
MSOP Package
206
Junction Temperature
150
C
Storage Temperature Range
-65
150
C
Lead Temperature (soldering, 10s)
300
C
V
IN
GND
V
L
V
OUT
FB
1
2
3
4
8
7
TOP VIEW
8-Pin TSSOP and MSOP
6
5
SHDN
LBI
LB0
FAN4855
PRODUCT SPECIFICATION
REV. 1.0.0 3/17/04
3
Recommended Operating Conditions
Electrical Characteristics
Unless otherwise specified, V
IN
= 1.6V to 3V, I
LOAD
= 1mA, T
A
= -40C to +85C. Test Circuit Fig.1. Typical values
are at T
A
= +25C
Notes:
1. R4, R5, R6 tolerance
0.1%.
2. Current through R1, R2 is not taken into account.
Parameter
Min.
Max.
Units
Temperature Range
-40
+85
C
V
IN
Operating Range
1.6
0.9 V
OUT
V
V
OUT
Operating Range
3.0
5.0
V
Parameter
Conditions
Min.
Typ.
Max.
Units
Start Up Voltage
I
LOAD
< 1mA
1.35
1.6
V
Operating Voltage
After start I
LOAD
=10mA, V
OUT
= 3.3V or
5V
1.0
V
Output Voltage
V
OUT
(nom.) = 3.3V (Note 1)
V
OUT
(nom.) = 5V
3.15
4.775
3.3
5
3.45
5.225
V
V
Output Voltage Adjust Range
3
5
V
Steady State Output Current
V
OUT
= 3.3V, V
IN
= 2.5V
300
500
mA
V
OUT
= 5V, V
IN
= 2.5V
200
330
mA
Pulse Width
V
IN
= 3V
0.8
1.4
2
s
V
IN
= 2.4V
1.2
1.7
2.5
s
V
IN
= 1.8V
1.6
2.2
3.3
s
V
IN
= 1.6V
1.7
2.5
4.0
s
Minimum Off-Time
1
s
Line Regulation
I
OUT
= 2mA, V
OUT
= 3.3V
0.5
2
%
V
OUT
= 5V
0.5
2
%
Load Regulation
0 to 250mA, V
IN
= 2.4V, V
OUT
= 3.3V
0.5
%
0 to 150mA, V
IN
= 2.4V, V
OUT
= 5V
1
%
Feedback Voltage (VFB)
1.243
V
LBI Threshold Voltage
0.390
V
LBI Hysteresys
25
mV
Internal NFET, PFET ON Resist. I
LOAD
= 100mA
0.35
Power Efficiency
I
LOAD
= 200mA, V
IN
= 3V, V
OUT
= 3.3V
95
%
Input Current in Shut Down
Mode
SHDN = 0V, V
IN
= 3V (Note 2)
8
50
A
Quiescent Current
SHDN = 3V, V
IN
= 3V, V
OUT
= 3.3V
(Note 2)
80
160
A
LBO Output Voltage Low
V
LBI
= 0, I
SINK
= 1mA
0.2
V
SHDN Input Threshold Voltage
V
IN
= 3V, V
OUT
= 3.3V/5V
1.5
V
SHDN Input Threshold Voltage
V
IN
= 1.6V, V
OUT
= 3.3V/5V
0.8
V
PRODUCT SPECIFICATION
FAN4855
4
REV. 1.0.0 3/17/04
Figure 1. Test Circuit
SHDN
C5
0.1F
JP3
R6
287K
1
2
1
2
GND1
1
2
1
2
1
2
U1
FAN4855
1
2
3
4
5
6
7
8
Vin
SHDN
LBI
LBO
FB
Vout
VL
Gnd
+
C3
18pF
R1
750K
R2
240K
R3
100K
C1
47
F
+ C2
47F
VOUT
3.3V or 5V
1
2
R5
240K
JP1
1
2
JP2
R4
402K
J1
SCOPE JACK
10uH
Reset
VIN
1.6V to 3.0V
Ext
Pull Up
GND
FAN4855
PRODUCT SPECIFICATION
REV. 1.0.0 3/17/04
5
Typical Operating Characteristics
(L = 10H, C
IN
= 47F, C
OUT
= 47F/1.0F, T = 25C)
Load Current vs. Start-Up Voltage
(Resistive Load)
Input Voltage, V
Load Current, mA
Efficiency vs. Load Current
Vout = 3.3V
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.1
1
10
100
1000
Output Current, mA
Efficiency, %
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.1
1
10
100
1000
Output Current, mA
Efficiency, %
Efficiency vs. Load Current
Vout = 5V
SHDN Threshold Voltage
Input Voltage, V
SHDN Voltage, V
Vin=2.0V
Vin=3V
Vin=1.5V
Vin=3V
Vin=2.0V
Vin=1.5V
0
100
200
300
400
500
600
1.5
2
2.5
3
3.5
4
V
OUT
= 5V
V
OUT
= 3.3V
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
2.1
2.3
1.5
2
2.5
3
3.5
4
4.5
Starting Up and Turning Off
V
OUT
= 3.3V, Iloads = 10mA to 50mA
Input Voltage, V
Output Voltage, V
Starting Up and Turning Off
V
OUT
= 5V, Iloads = 10mA to 50mA
Output Voltage, V
0
0.5
1
1.5
2
2.5
3
3.5
4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Input Voltage, V
0.6
0.8
1.0
1.2
1.4
1.6
1.8
START UP
START UP
TURN OFF:
TURN OFF:
Iload=50mA
Iload=50mA
Iload=10mA
Iload=10mA
Iload=10mA to 50mA
1
0
2
3
4
5