tors to run out of phase while using minimal input and
output capacitance. The operating supply voltage range
is from 20V down to 4V, making it suitable for dual, triple
or quadruple lithium-ion battery inputs as well as point
of load power supply applications from a 12V or 5V rail.
The operating frequency is programmable from 800kHz to
4MHz with an external resistor. The high frequency capa-
bility allows the use of small surface mount inductors. For
switching noise sensitive applications, it can be externally
synchronized from 800kHz to 4MHz. The PHMODE pin
allows user control of the phase of the outgoing clock
signal. The unique constant frequency/controlled on-time
architecture is ideal for high step-down ratio applications
that are operating at high frequency while demanding
fast transient response. Two internal phase-lock loops
synchronize the internal oscillator to the external clock
and also servos the regulator on-time to lock on to either
the internal clock or the external clock if it’s present.
L,
LT, LTC, LTM, PolyPhase, OPTI-LOOP, Linear Technology and the Linear logo 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,
5847554, 6580258, 6304066, 6476589, 6774611.
n
n
n
n
n
n
n
n
n
n
High Efficiency: Up to 96%
5A Output Current
4V to 20V V
IN
Range
Integrated Power N-Channel MOSFETs
(70mΩ Top and 35mΩ Bottom)
Adjustable Frequency 800kHz to 4MHz
PolyPhase
®
Operation (Up to 12 Phases)
Output Tracking
0.6V ±1% Reference Accuracy
Current Mode Operation for Excellent Line and Load
Transient Response
Shutdown Mode Draws Less Than 15µA Supply Cur-
rent
LTC3605: 15V Absolute Maximum V
IN
LTC3605A: 22V Absolute Maximum V
IN
The LTC3605A Is Pin Compatible with the LTC3605
Available in 24-Pin (4mm
×
4mm) QFN Package
applicaTions
n
n
n
n
Point of Load Power Supply
Portable Instruments
Distributed Power Systems
Battery-Powered Equipment
Typical applicaTion
High Efficiency 1MHz, 5A Step-Down Regulator
V
IN
4V TO 20V
22µF
×2
Efficiency and Power Loss
100
90
80
EFFICIENCY (%)
V
OUT
= 3.3V
10
PV
IN
CLKOUT
CLKIN
SV
IN
INTV
CC
70
60
50
40
30
20
10
0
0.01
0.1
1
LOAD CURRENT (A)
V
IN
= 8V
V
IN
= 12V
V
IN
= 20V
10
3605A TA01b
1
POWER LOSS (W)
2.2µF
0.1µF 1µH
11.5k
2.55k
16k
PGND
47µF
×2
BOOST
PGOOD
LTC3605A
SW
V
ON
V
IN
RUN
RT
FB
ITH
162k
V
OUT
3.3V
0.1
0.01
220pF
3605A TA01a
3605afc
For more information
www.linear.com/LTC3605A
1
LTC3605A
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
CLKOUT
INTV
CC
BOOST
CLKIN
SGND
SV
IN
18 PV
IN
17 PV
IN
25
PGND
16 SW
15 SW
14 SW
13 SW
7
RUN
8
PGOOD
9 10 11 12
PGND
SW
V
ON
SW
PV
IN
, SV
IN
, SW Voltage.............................. –0.3V to 22V
SW Transient Voltage ..................................–2V to 24.5V
BOOST Voltage ..........................–0.3V to PV
IN
+ INTV
CC
RUN Voltage.............................................. –0.3V to SV
IN
V
ON
Voltage............................................... –0.3V to SV
IN
INTV
CC
Voltage ......................................... –0.3V to 3.6V
ITH, RT, CLKOUT, PGOOD Voltage ........ –0.3V to INTV
CC
CLKIN, PHMODE, MODE Voltage .......... –0.3V to INTV
CC
TRACK/SS, FB Voltage .......................... –0.3V to INTV
CC
Operating Junction Temperature Range
(Note 2).................................................. –40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
24 23 22 21 20 19
RT 1
PHMODE 2
MODE 3
FB 4
TRACK/SS 5
ITH 6
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 25) IS PGND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3605AEUF#PBF
LTC3605AIUF#PBF
TAPE AND REEL
LTC3605AEUF#TRPBF
LTC3605AIUF#TRPBF
PART MARKING*
3605A
3605A
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°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/
elecTrical characTerisTics
SYMBOL
SV
IN
PV
IN
I
Q
PARAMETER
SV
IN
Supply Range
V
IN
Power Supply Range
Input DC Supply Current
Active
Shutdown
Feedback Reference Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
Feedback Pin Input Current
Error Amplifier Transconductance
Minimum On-Time
Minimum Off-Time
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
≈ T
A
= 25°C (Note 2). V
IN
= 12V unless otherwise noted.
CONDITIONS
MIN
4
1.2
(Note 3)
Mode = 0, R
T
= 162k
V
IN
=12V, RUN = 0
ITH =1.2V (Note 4)
V
IN
= 4V to 20V, ITH = 1.2V
l
l
l
TYP
MAX
20
20
UNITS
V
V
mA
µA
V
%/V
%
nA
mS
ns
ns
3605afc
1.5
11
0.594
0.600
0.001
0.1
1.15
1.35
40
70
5
40
0.606
0.03
0.3
±30
1.6
V
FB
DV
FB(LINE)
DV
FB(LOAD)
I
FB
g
m
(EA)
t
ON(MIN)
t
OFF(MIN)
ITH = 1.2V
2
For more information
www.linear.com/LTC3605A
LTC3605A
elecTrical characTerisTics
SYMBOL
I
LIM
R
TOP
R
BOTTOM
V
UVLO
V
RUN
V
INTVCC
DV
INTVCC
OV
UV
DV
FB(HYS)
R
PGOOD
I
PGOOD
I
TRACK/SS
f
OSC
CLKIN
V
VIN_OV
PARAMETER
Positive Inductor Valley Current Limit
Negative Inductor Valley Current Limit
Top Power NMOS On-Resistance
Bottom Power NMOS On-Resistance
INTV
CC
Undervoltage Lockout
Threshold
Run Threshold 2 (I
Q
≥ 1mA)
Run Threshold 1 (I
Q
≥ 100µA)
Internal V
CC
Voltage
INTV
CC
Load Regulation
Output Overvoltage
PGOOD Upper Threshold
Output Undervoltage
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Pull-Down Resistance
PGOOD Leakage
TRACK Pull-Up Current
Oscillator Frequency
CLKIN Threshold
V
IN
Overvoltage Lockout Threshold
R
T
= 162k
CLKIN V
IL
CLKIN V
IH
V
IN
Rising
V
IN
Falling
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
≈ T
A
= 25°C (Note 2). V
IN
= 12V unless otherwise noted.
CONDITIONS
MIN
5
INTV
CC
= 3.3V
INTV
CC
= 3.3V
INTV
CC
Falling
INTV
CC
Hysteresis (Rising)
RUN Rising
RUN Rising
4V < V
IN
< 20V
I
LOAD
= 0mA to 20mA
V
FB
Rising
V
FB
Falling
V
FB
Returning
0.54V < V
FB
< 0.66V
2.5
0.85
1
22.8
20.8
23.5
21.5
1
7
–13
2.4
1.1
0.45
3.2
TYP
6
–5
70
35
2.6
0.25
1.2
0.6
3.3
0.5
10
–10
1.5
12
25
2
4
1.2
0.3
24.2
22.1
13
–7
MAX
7.5
150
60
2.8
1.3
0.75
3.4
UNITS
A
A
mΩ
mΩ
V
V
V
V
V
%
%
%
%
Ω
µA
µA
MHz
V
V
V
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
reliability and lifetime. Absolute Maximum Ratings are those values
beyond which the life of a device may be impaired.
Note 2:
The LTC3605A is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3605AE (E-grade) 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
LTC3605AI (I-grade) is guaranteed over the full –40°C to 125°C operating
temperature range.
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. Note that the maximum
ambient temperature is determined by specific operating conditions
in conjunction with board layout, the rated thermal package thermal
resistance and other environmental factors.
Note 3:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 4:
The LTC3605A is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (ITH).
Note 5:
T
J
is calculated from the ambient temperature T
A
and
power dissipation as follows: T
J
= T
A
+ P
D
•
(37°C/W). See Thermal
Considerations section.
Note 6:
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
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