LINEAR TECHNOLOGY LT3473, LT3473A Technical data
FEATURES
■
Tiny Solution Size
■
Low Quiescent Current:
150µA in Active Mode (VIN = 3.6V, V
OUT
= 15V,
No Load)
1µA in Shutdown Mode
■
Internal 1A, 36V Switch
■
Integrated Schottky Diode
■
Integrated PNP Output Disconnect
■
Internal Reference Override Pin
■
PGOOD Pin
■
25V at 80mA from 3.6V Input
■
Auxiliary NPNs for Intermediate
Bias Voltages (LT3473A)
■
Automatic Burst Mode® Operation at Light Load
■
Constant Switching Frequency: 1.2MHz
■
Thermal Shutdown
■
Input Range: 2.2V to 16V
■
Low Profile (3mm × 3mm) DFN Package (LT3473)
■
Low Profile (4mm × 3mm) DFN Package (LT3473A)
U
APPLICATIO S
■
OLED Bias
■
CCD Bias
LT3473/LT3473A
Micropower 1A Boost
Converter with Schottky
and Output Disconnect
U
DESCRIPTIO
The LT®3473/LT3473A are micropower step-up DC/DC
converters with integrated Schottky diode and output
disconnect circuitry in low profile DFN packages. The
small package size, high level of integration and the use of
tiny SMT components yield a solution size of less than
2
50mm
25V at up to 80mA from a Li-Ion cell, while automatic Burst
Mode operation maintains efficiency at light load. An
auxiliary reference input (CTRL) allows the user to override the internal 1.25V feedback reference with any lower
value, allowing full control of the output voltage during
operation. A PGOOD pin sinks current when the output
voltage reaches 90% of final value.
The LT3473A includes two NPN transistors for generating
intermediate bias voltages from the output and is offered
in a 12-lead (4mm × 3mm) DFN package. The LT3473
does not include these NPNs and is offered in an 8-lead
(3mm × 3mm) package.
The rugged 36V switch and output disconnect circuitry
allow outputs up to 34V to be easily generated in a simple
boost topology.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
. The internal 1A switch allows the device to deliver
TYPICAL APPLICATIO
PGOOD
CTRL
SW
V
IN
SHDN
LT3473
GND
V
3V TO 4.2V
4.7µF
IN
6.8µH
OUT
CAP
FB
U
2M
100k
2.2µF
0.47µF
3473 TA01a
V
OUT
25V
80mA
Conversion Efficiency and Power Loss vs Output Current
3473 TA01b
100
500
400
300
200
100
0
POWER LOSS (mW)
3473f
80
VIN = 3.6V
= 15V
V
OUT
75
70
65
EFFICIENCY (%)
60
55
0.1
1
OUTPUT CURRENT (mA)
10
1
LT3473/LT3473A
12
11
10
9
8
7
1
2
3
4
5
6
SW
V
IN
SHDN
PGOOD
CTRL
FB
CAP
OUT
NB1
NE1
NB2
NE2
TOP VIEW
13
DE PACKAGE
12-LEAD (4mm × 3mm) PLASTIC DFN
WWWU
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Voltage ............................................................. 16V
SHDN Voltage .......................................................... 16V
SW Voltage ............................................................. 36V
PGOOD Voltage ...................................................... 36V
CAP Voltage ............................................................ 36V
OUT Voltage ........................................................... 36V
FB Voltage .............................................................. 10V
UU
W
PACKAGE/ORDER I FOR ATIO
TOP VIEW
1CAP
OUT
2
CTRL
3
FB
4
8-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
EXPOSED PAD (PIN 9) IS GND
MUST BE SOLDERED TO PCB (NOTE 3)
9
DD PACKAGE
= 125°C, θJA = 43°C/ W
8
7
6
5
SW
V
IN
SHDN
PGOOD
ORDER PART
NUMBER
LT3473EDD
DD PART MARKING
LBJJ
CTRL Voltage .......................................................... 10V
NB1, NB2 Voltage ................................................... 36V
NE1, NE2 Voltage ................................................... 36V
Maximum Junction Temperature ......................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................ –65°C to 125°C
ORDER PART
NUMBER
LT3473AEDE
DE PART MARKING
3473A
T
= 125°C, θJA = 43°C/ W
JMAX
EXPOSED PAD (PIN 13) IS GND
MUST BE SOLDERED TO PCB (NOTE 3)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VIN = 3V, SHDN = 3V, CTRL = 2V, unless otherwise specified.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Operation Voltage 2.2 V
Maximum Operation Voltage 16 V
Supply Current SHDN = 3V, Not Switching 100 µA
SHDN Voltage to Enable Chip ● 1.4 V
SHDN Voltage to Disable Chip ● 0.2 V
SHDN Pin Bias Current 2 µA
FB Voltage ● 1.235 1.25 1.26 V
FB Voltage Line Regulation 3V < VIN < 16V 0.01 %/V
FB Pin Bias Current FB = 1.27V 20 nA
CTRL to FB Offset CTRL = 0.5V 5 20 mV
CTRL Pin Bias Current CTRL = 1V 50 nA
FB Threshold for PGOOD CTRL = 2V 1.15 V
PGOOD Current Capacity ● 100 µA
2
SHDN = 0V 0.1 1 µA
CTRL = 0.5V 0.40 V
3473f
LT3473/LT3473A
CTRL VOLTAGE (V)
0
1.0
1.2
1.4
2
3473 G03
0.8
0.6
0.5 1 1.5
0.4
0.2
0
PGOOD THRESHOLD VOLTAGE (V)
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
= 3V, SHDN = 3V, CTRL = 2V, unless otherwise specified.
V
IN
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switching Frequency 0.9 1.2 1.4 MHz
Maximum Duty Cycle ● 88 92 %
Switch Current Limit ● 1.2 A
Switch V
CESAT
Switch Leakage Current VSW = 5V 0.1 5 µA
Schottky Forward Drop ID = 100mA 0.45 V
Schottky Leakage Current CAP = 36V, SW = 0V 4 µA
Disconnect PNP Voltage Drop I
Disconnect PNP Quiescent Current CAP = 20V 1.2 µA
Disconnect PNP Leakage Current SHDN = OUT = 0V, CAP = 20V 0.01 0.1 µA
LTC3473A Only
NPN1 Voltage Drop INE1 = 1mA 0.8 V
NPN1 Beta INE1 = 1mA 60
NPN2 Voltage Drop INE2 = 1mA 0.8 V
NPN2 Beta INE2 = 1mA 60
ISW = 100mA 45 mV
= 100µA, CAP = 20V 80 mV
OUT
= 50mA, CAP = 20V 250 mV
I
OUT
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT3473EDD and LT3473AEDE are guaranteed to meet
performance specifications from 0°C to 70°C. Specifications over the
–40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.
UW
TYPICAL PERFOR A CE CHARACTERISTICS
Load Regulation (Feedback Taken
from CAP)
20.20
VIN = 3.6V
20.00
19.80
19.60
VOLTAGE (V)
19.40
19.20
19.00
0
CAP
OUT
20 40 60 80
LOAD CURRENT (mA)
100
3473 G01
Feedback Voltage PGOOD Threshold Voltage
1.4
1.2
1.0
0.8
0.6
0.4
FEEDBACK VOLTAGE (V)
0.2
0
0
0.2
0.6
0.8
0.4
CTRL VOLTAGE (V)
Note 3: Failure to correctly solder the Exposed Pad of the package to the
PC board will result in a thermal resistance much higher than 40°C.
TA = 25°C unless otherwise noted.
1
1.2 1.6
1.4
1.8
3473 G02
2
3473f
3
LT3473/LT3473A
UW
TYPICAL PERFOR A CE CHARACTERISTICS
Sleep Mode Quiescent Current
Sleep Mode Quiescent Current
105
SHDN = 3V
= 3V
V
IN
100
(Not Switching)
102
100
98
96
SHDN = 3V
TA = 25°C unless otherwise noted.
SHDN Pin Current
2.5
SHDN = 3V
= 3V
V
IN
2.0
1.5
95
SLEEP MODE QUIESCENT CURRENT (µA)
90
–50
Switch V
450
400
350
300
250
200
150
100
50
SWITCH SATURATION VOLTAGE (mV)
0
0
050
TEMPERATURE (°C)
CE(SAT)
400
200
SWITCH CURRENT (mA)
600 1200
800
1000
3473 G04
3473 G07
100
94
92
90
SLEEP MODE QUIESCENT CURRENT (µA)
88
0
48
214
INPUT VOLTAGE, VIN (V)
SHDN = 1.5V
610 16
12
3473 G5
1.0
SHDN PIN CURRENT (µA)
0.5
0
–50
0
TEMPERATURE (°C)
Switch Saturation Voltage Schottky I-V Characteristic
50
= 100mA
I
SW
49
48
47
46
45
44
43
SWITCH SATURATION VOLTAGE (mV)
42
–50
050
TEMPERATURE (°C)
100
3473 G08
1000
900
800
700
600
500
400
300
200
SCHOTTKY FORWARD CURRENT (mA)
100
0
200
0
400
SCHOTTKY FORWARD DROP (mV)
600
50
800
100
3473 G06
1000
3473 G09
Schottky Forward Voltage
550
ID = 100mA
500
450
400
350
SCHOTTKY FORWARD VOLTAGE (mV)
300
–50
0
TEMPERATURE (°C)
4
Output Disconnect Voltage Drop
400
350
300
250
200
150
VOLTAGE DROP (mV)
100
50
50
100
3473 G10
0
20 40 60 100
0
COLLECTOR CURRENT (mA)
90°C
25°C
–45°C
80
3473 G11
Switching Frequency
1.4
1.2
1.0
0.8
0.6
0.4
SWITCHING FREQUENCY (MHz)
0.2
0
0
510
INPUT VOLTAGE, VIN (V)
15
3473 G12
3473f
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