extending the operating time in battery-powered systems.
The operating frequency is externally programmable up to
4MHz, allowing the use of small surface mount inductors.
For switching-noise-sensitive applications, the LTC3614
can be synchronized to an external clock at up to 4MHz.
Forced continuous mode operation in the LTC3614 reduces
noise and RF interference. Adjustable compensation allows
the transient response to be optimized over a wide range
of loads and output capacitors.
The internal synchronous switch increases efficiency and
eliminates the need for an external catch diode, saving
external components and board space. The LTC3614
is offered in a leadless 24-pin 3mm
×
5mm thermally
enhanced QFN package.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6580258, 5481178, 5994885, 6304066, 6498466, 6611131.
n
n
n
n
n
n
n
4A Output Current
2.25V to 5.5V Input Voltage Range
Low Output Ripple Burst Mode
®
Operation: I
Q
= 75µA
±1% Output Voltage Accuracy
Output Voltage Down to 0.6V
High Efficiency: Up to 95%
Low Dropout Operation: 100% Duty Cycle
Programmable Slew Rate on SW Node Reduces
Noise and EMI
Adjustable Switching Frequency: Up to 4MHz
Optional Active Voltage Positioning (AVP) with
Internal Compensation
Selectable Pulse-Skipping/Forced Continuous/Burst
Mode Operation with Adjustable Burst Clamp
Programmable Soft-Start
Inputs for Start-Up Tracking or External Reference
DDR Memory Mode, I
OUT
= ±3A
Available in a 24-Pin 3mm
×
5mm QFN
Thermally Enhanced Package
Point-of-Load Supplies
Distributed Power Supplies
Portable Computer Systems
DDR Memory Termination
Handheld Devices
applicaTions
n
n
n
n
n
Typical applicaTion
V
IN
2.7V TO 5.5V
SV
IN
PV
IN
SRLIM/DDR
RUN
TRACK/SS
RT/SYNC
LTC3614
SW
PGOOD
SGND
ITH
PGND
MODE
V
FB
210k
100
10µF
×4
EFFICIENCY (%)
90
80
70
60
50
40
30
20
10
0
1
Efficiency and Power Loss
vs Load Current
1
POWER LOSS (W)
330nH
47µF
×2
665k
3614 TA01a
V
OUT
2.5V
4A
0.1
0.01
V
OUT
= 2.5V
V
IN
= 2.8V
V
IN
= 3.3V
V
IN
= 5V
0
10
100
1000
OUTPUT CURRENT (mA)
10000
3614 TA01b
3614fc
For more information
www.linear.com/LTC3614
1
LTC3614
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
TRACK/SS
MODE
20 PGOOD
19 RUN
18 SV
IN
25
PGND
17 PV
IN
16 SW
15 SW
14 SW
13 SW
9
NC
10 11 12
PV
IN
PV
IN
NC
PV
IN
, SV
IN
Voltages ..................................... –0.3V to 6V
SW Voltage ................................. –0.3V to (PV
IN
+ 0.3V)
ITH, RT/SYNC Voltages ............... –0.3V to (SV
IN
+ 0.3V)
SRLIM, TRACK/SS Voltages ....... –0.3V to (SV
IN
+ 0.3V)
MODE, RUN, V
FB
Voltages .......... –0.3V to (SV
IN
+ 0.3V)
PGOOD Voltage ............................................ –0.3V to 6V
Operating Junction Temperature Range
(Notes 2, 11) .......................................... –55°C to 150°C
Storage Temperature.............................. –65°C to 150°C
24 23 22 21
SRLIM/DDR 1
RT/SYNC 2
SGND 3
PV
IN
4
SW 5
SW 6
SW 7
SW 8
UDD PACKAGE
24-LEAD (3mm
×
5mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 25) IS PGND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3614EUDD#PBF
LTC3614IUDD#PBF
LTC3614HUDD#PBF
LTC3614MPUDD#PBF
TAPE AND REEL
LTC3614EUDD#TRPBF
LTC3614IUDD#TRPBF
LTC3614HUDD#TRPBF
LTC3614MPUDD#TRPBF
PART MARKING*
LFVM
LFVM
LFVM
LFVM
PACKAGE DESCRIPTION
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
V
FB
ITH
2
3614fc
For more information
www.linear.com/LTC3614
LTC3614
elecTrical characTerisTics
SYMBOL
V
IN
V
UVLO
V
FB
PARAMETER
Operating Voltage Range
Undervoltage Lockout Threshold
Feedback Voltage Internal Reference
SV
IN
Ramping Down
SV
IN
Ramping Up
(Note 3) V
TRACK
= SV
IN
, V
DDR
= 0V
0°C < T
J
< 85°C
–40°C < T
J
< 125°C
–55°C < T
J
< 150°C
(Note 3) V
TRACK
= 0.3V, V
DDR
= SV
IN
(Note 3) V
TRACK
= 0.5V, V
DDR
= SV
IN
V
FB
= 0.6V
SV
IN
= PV
IN
= 2.25V to 5.5V
(Notes 3, 4) TRACK/SS = SV
IN
–40°C < T
J
< 125°C
–55°C < T
J
< 150°C
ITH from 0.5V to 0.8V (Notes 3, 4)
V
ITH
= SV
IN
(Note 5)
V
FB
= 0.5V, V
MODE
= SV
IN
(Note 6)
V
FB
= 0.7V, V
MODE
= 0V, ITH = SV
IN
(Note 5)
V
FB
= 0.7V, V
MODE
= 0V (Note 4)
Shutdown Current
R
DS(ON)
I
LIM
Top Switch On-Resistance
Bottom Switch On-Resistance
Top Switch Current Limit
SV
IN
= PV
IN
= 5.5V, V
RUN
= 0V
PV
IN
= 3.3V (Note 10)
PV
IN
= 3.3V (Note 10)
Sourcing (Note 8), V
FB
= 0.5V
Duty Cycle <35%
Duty Cycle = 100%
Sinking (Note 8), V
FB
= 0.7V,
Forced Continuous Mode
–5µA < I
ITH
< 5µA (Note 4)
(Note 4)
V
FB
from 0.06V to 0.54V,
TRACK/SS = SV
IN
(Note 7 )
0.65
0.62
60
200
RT/SYNC = 370k
V
RT/SYNC
= SV
IN
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 3.3V, RT/SYNC = SV
IN
unless otherwise specified.
CONDITIONS
l
l
l
MIN
2.25
1.7
TYP
MAX
5.5
2.25
UNITS
V
V
V
V
V
V
V
V
nA
l
l
0.594
0.591
0.589
0.288
0.488
0.6
0.606
0.609
0.609
0.312
0.512
±30
Feedback Voltage External Reference
(Note 7)
I
FB
∆V
LINEREG
Feedback Input Current
Line Regulation
0.300
0.500
l
l
0.2
0.3
0.25
2.6
1100
75
130
0.1
35
25
7.5
5
–6
9
–8
200
±30
1.2
1.9
10.5
–11
100
175
1
%/V
%/V
%
%
µA
µA
µA
µA
mΩ
mΩ
A
A
A
µS
µA
ms
V
µs
Ω
MHz
MHz
MHz
V
V
µA
V
∆V
LOADREG
I
S
Load Regulation
Active Mode Supply Current
Sleep Mode Supply Current
Bottom Switch Current Limit
g
m(EA)
I
EAO
t
SS
V
TRACK/SS
t
TRACK/SS_DIS
Error Amplifier Transconductance
Error Amplifier Maximum Output
Current
Internal Soft-Start Time
Enable Internal Soft-Start
Soft-Start Discharge Time at Start-Up
R
ON(TRACK/SS_DIS)
TRACK/SS Pull-Down Resistor at
Start-Up
f
OSC
f
SYNC
V
RT/SYNC
I
SW(LKG)
V
DDR
Oscillator Frequency
Internal Oscillator Frequency
Synchronization Frequency Range
SYNC Input Threshold High
SYNC Input Threshold Low
Switch Leakage Current
DDR Option Enable Voltage
SV
IN
= PV
IN
= 5.5V, V
RUN
= 0V
SV
IN
– 0.3
0.8
1.8
0.3
1.2
.
0.1
1
2.25
1.2
2.7
4
0.3
1
3614fc
For more information
www.linear.com/LTC3614
3
LTC3614
elecTrical characTerisTics
SYMBOL
V
MODE
(Note 9)
PARAMETER
Internal Burst Mode Operation
Pulse-Skipping Mode
Forced Continuous Mode
External Burst Mode Operation
PGOOD
Power Good Voltage Windows
TRACK/SS = SV
IN
, Entering Window
V
FB
Ramping Up
V
FB
Ramping Down
TRACK/SS = SV
IN
, Leaving Window
V
FB
Ramping Up
V
FB
Ramping Down
t
PGOOD
R
PGOOD
V
RUN
Power Good Blanking Time
Power Good Pull-Down On-Resistance
RUN voltage
Input High
Input Low
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 3.3V, RT/SYNC = SV
IN
unless otherwise specified.
CONDITIONS
MIN
SV
IN
– 0.3
1.1
0.45
–3
3
–6
6
9
–9
70
8
1
105
17
11
–11
140
33
0.4
SV
IN
• 0.58
0.8
TYP
MAX
0.3
UNITS
V
V
V
V
%
%
%
%
µs
Ω
V
V
Entering and Leaving Window
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
reliability and lifetime.
Note 2:
The LTC3614 is tested under pulsed load conditions such that T
J
≈
T
A
. The LTC3614E is guaranteed to meet specifications from 0°C to 85°C
junction temperature. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3614I is guaranteed
to meet specifications over the –40°C to 125°C operating junction
temperature, the LTC3614H is guaranteed to meet specifications over the
–40°C to 150°C operating junction temperature range and the LTC3614MP
is guaranteed and tested to meet specifications over the full –55°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes; operating lifetime is derated for temperature
greater than 125°C. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance and other environmental factors.
The junction temperature (T
J
) is calculated from the ambient temperature
(T
A
) and power dissipation (P
D
) according to the formula: T
J
= T
A
+ (P
D
•
θ
JA
°C/W), where
θ
JA
is the package thermal impedance. The maximum
ambient temperature is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistance and
other environmental factors.
Note 3:
This parameter is tested in a feedback loop which servos V
FB
to
the midpoint for the error amplifier (V
ITH
= 0.75V).
Note 4:
External compensation on ITH pin.
Note 5:
Tying the ITH pin to SV
IN
enables the internal compensation and
AVP mode.
Note 6:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 7:
See description of the TRACK/SS pin in the Pin Functions section.
Note 8:
In sourcing mode the average output current is flowing out of the
SW pin. In sinking mode the average output current is flowing into the SW
Pin.
Note 9:
See description of the MODE pin in the Pin Functions section.
Note 10:
Guaranteed by correlation and design to wafer level
measurements for QFN packages.
Note 11:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
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Test/Measurement
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