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PDF LTC3619B Data sheet ( Hoja de datos )
| Número de pieza | LTC3619B | |
| Descripción | 400mA/800mA Synchronous Step-Down DC/DC | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3619Bwww.DataSheet4U.com
400mA/800mA Synchronous
Step-Down DC/DC with
Average Input Current Limit
Features
Description
n Programmable Average Input Current Limit:
±5% Accuracy
n Dual Step-Down Outputs: Up to 96% Efficiency
n Low Noise Pulse-Skipping Operation at Light Loads
n Input Voltage Range: 2.5V to 5.5V
n Output Voltage Range: 0.6V to 5V
n 2.25MHz Constant-Frequency Operation
n Power Good Output Voltage Monitor for Each Channel
n Low Dropout Operation: 100% Duty Cycle
n Independent Internal Soft-Start for Each Channel
n Current Mode Operation for Excellent Line and Load
Transient Response
n ±2% Output Voltage Accuracy
n Short-Circuit Protected
n Shutdown Current ≤ 1μA
n Available in Small Thermally Enhanced 10-Lead MS
and 3mm × 3mm DFN Packages
Applications
n High Peak Load Current Applications
n USB Powered Devices
n Supercapacitor Charging
n Radio Transmitters and Other Handheld Devices
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S.Patents, including 5481178, 6127815,
6304066, 6498466, 6580258, 6611131.
The LTC®3619B is a dual monolithic synchronous buck
regulator using a constant frequency current mode ar-
chitecture.
The input supply voltage range is 2.5V to 5.5V, making it
ideal for Li-Ion and USB powered applications. 100% duty
cycle capability provides low dropout operation, extend-
ing the run time in battery-operated systems. Low output
voltages are supported with the 0.6V feedback reference
voltage. Channel 1 and channel 2 can supply 400mA and
800mA output current, respectively.
The LTC3619B’s programmable average input current limit
is ideal for USB applications and for point-of-load power
supplies because the LTC3619B’s limited input current
will still allow its output to deliver high peak load currents
without collapsing the input supply. When the sum of
both channels’ currents exceeds the input current limit,
channel 2 is current limited while channel 1 remains regu-
lated. The operating frequency is internally set at 2.25MHz
allowing the use of small surface mount inductors. Internal
soft-start reduces in-rush current during start-up. The
LTC3619B is available in small MSOP and 3mm × 3mm
DFN packages. The LTC3619B is also available in a low
quiescent current, high efficiency Burst Mode® version,
LTC3619.
Typical Application
Dual Monolithic Buck Regulator in 10-Lead 3mm × 3mm DFN
VIN
3.4V TO 5.5V
10µF
RUN2 VIN RUN1
PGOOD2 PGOOD1
VOUT2
3.4V AT
800mA
1.5µH
LTC3619B
SW2 SW1
3.3µH
22pF
1190k
+
VFB2
VFB1
2.2mF
s2
255k
RLIM GND
SuperCap
255k 511k
1000pF
116k
ILIM = 475mA
VOUT1
1.8V AT
400mA
10µF
3619B TA01
GSM Pulse Load
VOUT
200mV/DIV
VIN
AC-COUPLED
1V/DIV
IOUT
500mA/DIV
IIN
500mA/DIV
1ms/DIV
3619B TA01b
VIN = 5V, 500mA COMPLIANT
ILOAD = 0A to 2.2A, CHANNEL 1 UNLOADED
3619bfa
1 page  
LTC3619Bwww.DataSheet4U.com
Typical Performance Characteristics TA = 25°C, VIN = 5V, unless otherwise noted.
Efficiency vs Load Current
100
90 CVHOUATN=NE3L.31V
80
70
60
50
40
30
20
10
0
0.0001
VVVIIINNN
=
=
=
3.6V
4.2V
5V
0.001
0.01
0.1
OUTPUT CURRENT (A)
1
3619B G10
Efficiency vs Load Current
100
90 CVHOUATN=NE3L.32V
80
70
60
50
40
30
20
10
0
0.0001
VVVIIINNN
=
=
=
3.6V
4.2V
5V
0.001
0.01
0.1
OUTPUT CURRENT (A)
1
3619B G11
Efficiency vs Load Current
100
90 CVHOUATN=NE1L.21V
80
70
60
50
40
30
20
10
0
0.0001
VVVVIIIINNNN
=
=
=
=
2.7V
3.6V
4.2V
5V
0.001
0.01
0.1
OUTPUT CURRENT (A)
1
3619B G12
Efficiency vs Load Current
100
90
CVHOUATN=NE1L.22V
80
70
60
50
40
30
20
10
0
0.0001
VVVVIIIINNNN
=
=
=
=
2.7V
3.6V
4.2V
5V
0.001
0.01
0.1
OUTPUT CURRENT (A)
1
3619B G13
Load Regulation
3.0 CHANNEL 1
2.5
2.0
1.5
1.0
0.5
0
–0.5
–1.0
0
VVVOOOUUUTTT
=
=
=
1.8V
2.5V
3.3V
100 200 300 400
LOAD CURRENT (mA)
3619B G14
Load Regulation
3.0
CHANNEL 2
2.5
2.0
1.5
1.0
0.5
0
–0.5
–1.0
0
VVVOOOUUUTTT
=
=
=
1.8V
2.5V
3.3V
100 200 300 400 500 600 700 800
LOAD CURRENT (mA)
3619B G15
Line Regulation
0.6
0.4
IVLOOUATD
= 1.8V
= 100mA
Start-Up from Shutdown
RUN
2V/DIV
0.2
0
VOUT
1V/DIV
–0.2
IL
250mA/DIV
–0.4
–0.6
2.5 3.0 3.5 4.0 4.5 5.0 5.5
VIN (V)
3619B G16
200µs/DIV
VIN = 5V, VOUT = 3.3V
RLOAD = 7Ω
CLOAD = 4.7µF
Start-Up from Shutdown
RUN
2V/DIV
VOUT
2V/DIV
RLIM
1V/DIV
3619B G17
IIN
500mA/DIV CHANNEL 2
2ms/DIV
VIN = 5V, VOUT = 3.4V
RL = NO LOAD, CL = 4.4mF
CLIM = 2200pF, ILIM = 500mA
3619B G18
3619bfa
5 Page 
LTC3619Bwww.DataSheet4U.com
Applications Information
A general LTC3619B application circuit is shown in Figure 2.
External component selection is driven by the load require-
ment, and begins with the selection of the inductor L. Once
the inductor is chosen, CIN and COUT can be selected.
Inductor Selection
Although the inductor does not influence the operat-
ing frequency, the inductor value has a direct effect on
ripple current. The inductor ripple current DIL decreases
with higher inductance and increases with higher VIN or
VOUT :
ΔIL
=
VOUT
fO • L
•
1−
VOUT
VIN
(1)
Accepting larger values of DIL allows the use of low
inductances, but results in higher output voltage ripple,
greater core losses, and lower output current capability.
A reasonable starting point for setting ripple current is
40% of the maximum output load current. So, for a 800mA
regulator, DIL = 320mA (40% of 800mA).
The inductor value will also have an effect on Burst Mode
operation. The transition to low current operation begins
when the peak inductor current falls below a level set by
the internal burst clamp. Lower inductor values result in
higher ripple current which causes the transition to occur
at lower load currents. This causes a dip in efficiency in
the upper range of low current operation. Furthermore,
lower inductance values will cause the bursts to occur
with increased frequency.
VIN
2.5V TO 5.5V
VOUT2
C1
L2
CF2
RUN2 VIN RUN1
PGOOD2 PGOOD1
LTC3619B
SW2 SW1
L1
CF1
VOUT1
COUT2
R4
VFB2
R3 RLIM
VFB1
GND
CLIM RLIM
R1 R2
COUT1
3619B F02
Inductor Core Selection
Different core materials and shapes will change the size/cur-
rent and price/current relationship of an inductor. Toroid
or shielded pot cores in ferrite or permalloy materials are
small and do not radiate much energy, but generally cost
more than powdered iron core inductors with similar
electrical characteristics. The choice of which style induc-
tor to use often depends more on the price versus size
requirements, and any radiated field/EMI requirements,
than on what the LTC3619B requires to operate. Table 1
shows some typical surface mount inductors that work
well in LTC3619B applications.
Table 1. Representative Surface Mount Inductors
MANU-
MAX DC
FACTURER PART NUMBER VALUE CURRENT DCR HEIGHT
Coilcraft
LPS4012-152ML
LPS4012-222ML
LPS4012-332ML
LPS4012-472ML
LPS4018-222ML
LPS4018-332ML
LPS4018-472ML
1.5µH
2.2µH
3.3µH
4.7µH
2.2µH
3.3µH
4.7µH
2200mA
1750mA
1450mA
1450mA
2300mA
2000mA
1800mA
0.070Ω
0.100Ω
0.100Ω
0.170Ω
0.070Ω
0.080Ω
0.125Ω
1.2mm
1.2mm
1.2mm
1.2mm
1.8mm
1.8mm
1.8mm
FDK FDKMIPF2520D 4.7µH 1100mA 0.11Ω 1mm
FDKMIPF2520D 3.3µH 1200mA 0.1Ω 1mm
FDKMIPF2520D 2.2µH 1300mA 0.08Ω 1mm
Murata LQH32CN4R7M23 4.7µH 450mA 0.2Ω 2mm
Panasonic ELT5KT4R7M 4.7µH 950mA 0.2Ω 1.2mm
Sumida
CDRH2D18/LD
CDH38D11SNP-
3R3M
CDH38D11SNP-
2R2M
4.7µH
3.3μH
2.2μH
630mA
1560mA
1900mA
0.086Ω
0.115Ω
0.082Ω
2mm
1.2mm
1.2mm
Taiyo Yuden CB2016T2R2M
CB2012T2R2M
CB2016T3R3M
NR30102R2M
NR30104R7M
2.2µH
2.2µH
3.3µH
2.2µH
4.7µH
510mA
530mA
410mA
1100mA
750mA
0.13Ω
0.33Ω
0.27Ω
0.1Ω
0.19Ω
1.6mm
1.25mm
1.6mm
1mm
1mm
TDK VLF3010AT4R7- 4.7µH 700mA 0.28Ω 1mm
MR70
VLF3010AT3R3- 3.3µH 870mA 0.17Ω 1mm
MR87
VLF3010AT2R2- 2.2µH 1000mA 0.12Ω 1mm
M1R0
VLF4012AT-2R2 2.2µH 1500mA 0.076Ω 1.2mm
M1R5
VLF5012ST-3R3 3.3μH 1700mA 0.095Ω 1.2mm
M1R7
VLF5014ST-2R2 2.2µH 2300mA 0.059Ω 1.4mm
M2R3
Figure 2. LTC3619B General Schematic
3619bfa
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC3619B.PDF ] | |
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