LTC3422
1.5A, 3MHz Synchronous
Step-Up DC/DC Converter
with Output Disconnect
FEATURES
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DESCRIPTIO
700mA Continuous/1A Pulsed Output Current
for Li-Ion to 5V Applications
Synchronous Rectification: Up to 96% Efficiency
True Output Disconnect
Inrush Current Limiting
Adjustable Automatic Burst Mode
®
Operation
Low Noise, Fixed Frequency Operation from
100kHz to 3MHz
0.5V to 4.5V Input Range
2.25V to 5.25V Adjustable Output Voltage
Guaranteed 1V Start-Up
Programmable Soft-Start
Synchronizable Oscillator
Low Quiescent Current: 25µA
< 1µA Shutdown Current
Anti-Ringing Control
Small (3mm
×
3mm
×
0.75mm) Thermally Enhanced
10-Pin DFN Package
The LTC
®
3422 is a high efficiency, current mode, fixed
frequency, step-up DC/DC converter with true output
disconnect and inrush current limiting. The part is guaran-
teed to start up from an input voltage of 1V. The device
includes a 0.20Ω N-channel MOSFET switch and a 0.24Ω
P-channel MOSFET synchronous rectifier. The output
voltage, switching frequency, soft-start time, Burst Mode
threshold and loop compensation are all simply pro-
grammed using tiny external passive components.
Quiescent current is only 25µA during Burst Mode opera-
tion, maximizing battery life in portable applications. The
oscillator frequency can be programmed up to 3MHz and
can be synchronized to an external clock applied to the
SYNC pin.
Other features include 1µA shutdown, short-circuit protec-
tion, anti-ringing control, thermal shutdown and current
limit. The LTC3422 is available in a (3mm
×
3mm
×
0.75mm)
10-pin DFN package.
, LT, LTC and LTM 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.
APPLICATIO S
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Wireless Handsets
Handheld Computers
GPS Receivers
MP3 Players
TYPICAL APPLICATIO
V
IN
1.8V TO 3.2V
2 CELLS
2.4V to 3.3V Efficiency and Power Loss
100
10000
BURST
EFFICIENCY
1000
PWM
EFFICIENCY
POWER LOSS (mW)
4.7µH
90
80
+
4.7µF
V
IN
SYNC
LTC3422
OFF ON
SHDN
V
C
1nF
15k
22pF
SS
0.1µF
R
T
FB
BURST
GND
28k
2.2nF
301k
549k
SW
V
OUT
22µF
931k
EFFICIENCY (%)
V
OUT
3.3V
600mA
70
60
50
40
30
20
10
0
0.1
1
3422 TA01a
U
100
PWM
POWER
LOSSES
BURST
POWER
LOSSES
10
1
f
OSC
= 1MHz
10
100
LOAD CURRENT (mA)
0
1000
3422 TA01b
U
U
3422fa
1
LTC3422
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SW
V
IN
BURST
SS
SHDN
1
2
3
4
5
11
10 V
OUT
9 SYNC
8 R
T
7 V
C
6 FB
V
IN
, V
OUT
, SYNC Voltages ........................... – 0.3V to 6V
FB, SS, BURST, SHDN Voltages ................ – 0.3V to 6V
SW Voltage
DC .......................................................... – 0.3V to 6V
Pulsed < 100ns ...................................... – 0.3V to 7V
Operating Temperature Range
(Notes 2, 5) ............................................. –40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER
LTC3422EDD
DD PART MARKING
LBRN
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
OUT
= 3.3V, R
T
= 28k, unless otherwise noted. (Note 2)
PARAMETER
Minimum V
IN
Start-Up Voltage
Minimum V
IN
Operating Voltage
Output Voltage Adjust Range
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
I
LOAD
< 1mA
(Note 3)
●
MIN
TYP
0.88
MAX
1
0.5
5.25
5.25
UNITS
V
V
V
V
V
nA
µA
µA
mA
µA
µA
Ω
Ω
A
A
A
mA
%
2.25
2.40
1.192
1.216
1
25
0.1
0.75
0.1
0.1
0.20
0.24
Feedback Voltage
Feedback Input Current
Quiescent Current—Burst Mode Operation
Quiescent Current—Shutdown
Quiescent Current—Active
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
NMOS Current Limit—Steady State
NMOS Current Limit—Pulsed
NMOS Current Limit—Short Circuit
NMOS Burst Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Frequency
SYNC Input High
SYNC Input Low
SYNC Input Current
V
OUT
= 2V
V
OUT
= 3.3V
V
OUT
= 3.3V
V
FB
= 1.216V
V
C
= 0V (Note 4)
SHDN = 0V, V
OUT
= 0V
V
C
= 0V (Note 4)
●
1.240
50
42
1
1.1
5
10
●
Duty Cycle Not to Exceed 5%
V
OUT
= 500mV, V
IN
= 2.5V
●
●
●
●
●
1.5
2
2.5
0.75
600
91
1.5
84
0.85
2.2
0
1
1.15
0.8
0.01
1
3422fa
2
U
%
MHz
V
V
µA
W
U
U
W W
W
LTC3422
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
OUT
= 3.3V, R
T
= 28k, unless otherwise noted. (Note 2)
PARAMETER
SHDN Input High
SHDN Input Low
SHDN Input Current
Error Amp Transconductance
Soft-Start Current Source
BURST Threshold Voltage
V
SS
= 1V
Falling Edge, Sensed at the BURST Pin
–5
0.79
CONDITIONS
V
OUT
= 0V (Turn-On Threshold, Initial Start-Up)
V
OUT
> 2.4V (Stay-On Threshold)
Turn-Off Threshold
V
SHDN
= 3.3V
●
ELECTRICAL CHARACTERISTICS
MIN
1
0.65
TYP
MAX
UNITS
V
V
0.25
0.01
50
–2.4
0.88
–1.2
0.97
1
V
µA
µS
µA
V
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliabilty and lifetime.
Note 2:
The LTC3422E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
Once V
OUT
is greater than 2.4V, the LTC3422 is not dependent on
the V
IN
supply.
Note 4:
Current is measured into the V
OUT
pin since the supply current is
bootstrapped to the output. The current will reflect to the input supply by
(V
OUT
/V
IN
) • Efficiency. The outputs are not switching.
Note 5:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
3422fa
3
LTC3422
TYPICAL PERFOR A CE CHARACTERISTICS
(T
A
= 25°C, unless otherwise specified)
Single Cell to 3.3V Efficiency
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
60
50
40
30
20
10
0
0.1
f
OSC
= 1MHz
1
BURST
EFFICIENCY
V
IN
= 1.6V
V
IN
= 1.25V
V
IN
= 0.9V
PWM
EFFICIENCY
V
IN
= 1.6V
V
IN
= 1.25V
V
IN
= 0.9V
60
50
40
30
20
10
EFFICIENCY (%)
70
10
100
LOAD CURRENT (mA)
Burst Mode Operation
V
OUT
50mV/DIV
AC COUPLED
SW
2V/DIV
INDUCTOR
CURRENT
0.5A/DIV
V
IN
= 2.4V
I
LOAD
= 20mA
2µs/DIV
3422 G04
Efficiency vs Frequency
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1
V
IN
= 2.4V
V
OUT
= 3.3V
10
100
OUTPUT CURRENT (mA)
1000
3422 G07
f
OSC
= 300kHz
90
80
70
60
50
40
1
1.5
2
2.5 3
3.5 4
INPUT VOLTAGE (V)
4.5
5
f
OSC
= 1MHz
V
OUT
= 3.3V
PWM AT 200mA LOAD
START VOLTAGE (V)
f
OSC
= 3MHz
EFFICIENCY (%)
f
OSC
= 1MHz
4
U W
3422 G01
2-Cell to 3.3V Efficiency
100
90
80
70
Li-Ion to 5V Efficiency
100
90
80
BURST
EFFICIENCY
V
IN
= 3V
V
IN
= 2.4V
V
IN
= 1.8V
PWM
EFFICIENCY
V
IN
= 3V
V
IN
= 2.4V
V
IN
= 1.8V
f
OSC
= 1MHz
1
10
100
LOAD CURRENT (mA)
1000
3422 G02
70
60
50
40
30
20
10
0
0.1
1
PWM
EFFICIENCY
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3.1V
BURST
EFFICIENCY
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3.1V
1000
0
0.1
f
OSC
= 1MHz
1000
3422 G03
10
100
LOAD CURRENT (mA)
Load Transient Response
V
OUT
100mV/DIV
AC COUPLED
300mA
I
OUT
100mA/DIV
50mA
V
IN
= 2.4V
V
OUT
= 3.3V
C
OUT
= 22µF
200µs/DIV
3422 G05
Inrush Current Control
V
OUT
1V/DIV
INDUCTOR
CURRENT
100mA/DIV
V
IN
= 0V TO 2.4V 500µs/DIV
V
OUT
= 3.3V
C
OUT
= 22µF
100mA LOAD CURRENT
3422 G06
Efficiency vs V
IN
100
Start-Up Voltage vs Output Current
1.25
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0
100
50
150
OUTPUT CURRENT (mA)
200
3422 G09
3422 G08
3422fa
LTC3422
TYPICAL PERFOR A CE CHARACTERISTICS
(T
A
= 25°C, unless otherwise specified)
Burst Mode Output Current
Threshold vs R
BURST
(3.3V Output)
140
120
V
IN
= 1.25V TO 2.9V
V
OUT
= 3.3V
f
OSC
= 1MHz
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
80
80
ENTERS BURST (MIN)
60
40
20
EXITS BURST (AVE)
VOLTAGE (V)
100
60
ENTERS BURST (MIN)
40
20
EXITS BURST (AVE)
0
50
150 250
350
450
550 650 750 850
R
BURST
(kΩ)
3422 G10
Frequency vs Temperature
(Normalized About 1MHz)
1.02
30
QUIESCENT CURRENT (µA)
1.01
FREQUENCY (MHz)
1.00
26
CURRENT (A)
0.99
0.98
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
R
DS(ON)
vs Temperature
280
260
240
220
NMOS R
DS(ON)
200
180
160
–45 –30 –15
INPUT CURRENT (µA)
OUTPUT CURRENT (mA)
RESISTANCE (mΩ)
PMOS R
DS(ON)
0 15 30 45 60
TEMPERATURE (°C)
U W
75
3422 G13
Burst Mode Output Current
Threshold vs R
BURST
(5V Output)
140
120
100
V
IN
= 1.8V TO 4.2V
V
OUT
= 5V
f
OSC
= 1MHz
1.217
FB Voltage vs Temperature
1.216
1.215
1.214
0
50
125 200 275 350 425 500 575 650
R
BURST
(kΩ)
3422 G11
1.213
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3422 G12
Burst Mode Quiescent Current
vs Temperature
2.55
Current Limit vs Temperature
28
2.50
2.45
24
2.40
90
22
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
2.35
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3422 G14
3422 G15
No-Load Input Current vs V
IN
170
160
150
140
130
120
110
100
90
80
70
60
50
75
90
Maximum Output Current vs V
IN
2000
1800
1600
1400
1200
1000
800
600
V
OUT
= 3.3V
V
OUT
= 5V
5V DIODE
RECTIFICATION
3.3V DIODE
RECTIFICATION
f
OSC
= 1MHz
CHIP ENTERS
Burst Mode OPERATION
V
OUT
= 5V
V
OUT
= 3.3V
0.8 1.2 1.6
2 2.4 2.8 3.2 3.6
INPUT VOLTAGE (V)
4 4.4 4.8
3422 G17
400
1.80
2.40
3.00
3.60 4.20 4.80
INPUT VOLTAGE (V)
5.40
3422 G18
3422 G16
3422fa
5
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