Controlled On-Time Valley Current Mode Architecture,
Excellent Current Sharing Capability
Frequency Programmable from 200kHz to 1MHz
and Synchronizable to External Clock
R
SENSE
or Inductor DCR Current Sensing With
Accurate Current Limit
Fast Transient Response
Differential Output Voltage Sensing Allowing 500mV
Common Mode Remote Ground
t
ON(MIN)
= 65ns; t
OFF(MIN)
= 105ns
Overvoltage Protection and Current Limit Foldback
Power Good Output Voltage Monitor
Voltage Tracking Start-Up
External V
CC
Input for Bypassing Internal LDO
Micropower Shutdown: I
Q
= 15μA
7mm
×
9mm 56-pin QFN Package
APPLICATIONS
n
n
n
Distributed Power System
Point-of-Load Converters
Servers
TYPICAL APPLICATION
High Efficiency High Power Step-Down Converter
INTV
CC
PV
IN
SV
IN
LTC3613
V
OUT
PGOOD
SENSE
RUN
V
RNG
0.1μF
47pF
270pF
MODE/PLLIN
EXTV
CC
TRACK/SS
SENSE
+
–
Efficiency and Power Loss
vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
V
IN
= 12V
V
OUT
= 1.5V
0.1
10
1
LOAD CURRENT (A)
3613 TA01a
+
0.1μF
10Ω
1000pF
10Ω
0.47μH
82μF
V
IN
4.5V TO 24V
3.5
PULSE-SKIPPING MODE
3.0
2.5
FORCED
CONTINUOUS
MODE
2.0
1.5
1.0
0.5
0
POWER LOSS (W)
100k
1.5mΩ
15k
SW
0.1μF
BOOST
INTV
CC
10k
4.7μF
V
OUT
1.5V
15A
10
330μF
×2
0
0.01
21k
ITH
115k
RT
SGND
+
PGND
V
OSNS+
V
OSNS–
3613 TA01
3613fa
1
LTC3613
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
56 PV
IN
55 PV
IN
54 PV
IN
53 PV
IN
52 NC
51 SW
50 SW
49 SW
48 SW
47 SW
46 SW
45 SW
PV
IN
1
PV
IN
2
PV
IN
3
PV
IN
4
PV
IN
5
PV
IN
6
PV
IN
7
PV
IN
8
PV
IN
9
SW 10
BOOST 11
SGND 12
PGOOD 13
SNS+ 14
SNS– 15
SGND 16
PV
IN
57
SW
58
SGND
59
44 PGND
43 PGND
42 PGND
41 PGND
40 PGND
39 PGND
38 PGND
37 PGND
36 PGND
35 SW
34 INTV
CC
33 INTV
CC
32 SV
IN
31 MODE/PLLIN
30 EXTV
CC
29 SGND
WKH PACKAGE
56-LEAD (7mm
×
9mm) MULTIPAD QFN
T
JMAX
= 125°C,
θ
JA
= 29°C/W
Supply Voltage (PV
IN
, SV
IN
)....................... –0.3V to 24V
Boost Voltage ............................................ –0.3V to 30V
SW Voltage ................................................ –0.3V to 24V
INTV
CC
, EXTV
CC
, (BOOST-SW), MODE /PLLIN,
V
RNG
, PGOOD, RUN Voltages....................... –0.3V to 6V
V
OSNS+
, V
OSNS –
Voltages ........ –0.6V to (INTV
CC
+ 0.3V)
V
OUT
, SENSE
+,
SENSE
–
Voltages ................. –0.6V to 6V
RT, ITH Voltages ..................... –0.3V to (INTV
CC
+ 0.3V)
TRACK/SS Voltages ..................................... –0.3V to 5V
Operating Junction Temperature Range
(Notes 2, 4) ............................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
ORDER INFORMATION
LEAD FREE FINISH
LTC3613EWKH#PBF
LTC3613IWKH#PBF
TAPE AND REEL
LTC3613EWKH#TRPBF
LTC3613IWKH#TRPBF
PART MARKING*
LTC3613WKH
LTC3613WKH
PACKAGE DESCRIPTION
56-Lead (7mm
×
9mm) Plastic QFN
56-Lead (7mm
×
9mm) 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.
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/
SGND 17
V
OUT
18
SGND 19
V
OSNS
– 20
V
OSES
+ 21
TRACK/SS 22
ITH 23
V
RNG
24
RT 25
RUN 26
NC 27
SGND 28
3613fa
2
LTC3613
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
OUT
I
Q
PARAMETER
Input Voltage Operating Range
Output Voltage Operating Range
Input DC Supply Current
Normal
Shutdown Supply Current
Regulated Differential Feedback Voltage
(V
OSNS+
– V
OSNS–
)
MODE/PLLIN = INTV
CC
RUN = 0V
I
TH
= 1.2V (Note 3)
T
A
= 25°C
T
A
= 0°C to 85°C
T
A
= –40°C to 125°C
V
IN
= 4.5V to 24V, ITH = 0.5V to 1.9V,
V
OSNS–
= ±500mV (Note 3)
T
A
= 0°C to 85°C
T
A
= –40°C to 125°C
0.5985
0.596
0.594
Main Control Loop
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. SV
IN
= 15V, V
FB
= V
OSNS+
– V
OSNS–
, unless otherwise noted. (Note 4)
CONDITIONS
MIN
4.5
0.6
2
15
0.6
0.6
0.6
TYP
MAX
24
5.5
4
25
0.6015
0.604
0.606
UNITS
V
V
mA
μA
V
V
V
V
REG
l
l
Regulated Differential Feedback
Voltage Over Line, Load and Common Mode
(V
OSNS+
– V
OSNS–
)
t
ON(MIN)
t
OFF(MIN)
g
m(EA)
V
SENSE(MAX)
Minimum On-Time
Minimum Off-Time
Error Amplifier Transconductance
Valley Current Sense Threshold,
V
SENSE+
– V
SENSE–
,
Peak Current = Valley + Ripple
l
l
0.594
0.591
0.6
0.6
65
105
0.606
0.609
V
V
ns
ns
I
TH
= 1.2V (Note 3)
V
RNG
= 2V, V
FB
= 0.57V
V
RNG
= 0V, V
FB
= 0.57V
V
RNG
= INTV
CC
, V
FB
= 0.57V
l
l
l
l
1.4
80
22
39
1.7
100
30
50
–50
–15
–25
2
120
38
61
mS
mV
mV
mV
mV
mV
mV
V
SENSE(MIN)
Minimum Current Sense Threshold,V
SENSE+
– V
RNG
= 2V, V
FB
= 0.63V
V
SENSE–
, Force Continuous Operation
V
RNG
= 0V, V
FB
= 0.63V
V
RNG
= INTV
CC
, V
FB
= 0.63V
SENSE
+
, SENSE
–
Voltage Range (Common
Mode)
SENSE
+
, SENSE
–
Input Bias Current
RUN Pin On Threshold
RUN Pin Hysteresis
Soft-Start Charging Current
INTV
CC
Undervoltage Lockout
INTV
CC
Undervoltage Lockout Release
V
OSNS+
Input Bias Current
V
OSNS–
Input Bias Current
V
TRACKSS
= 0V
Falling
Rising
V
FB
= 0.6V
V
FB
= 0.6V
l
l
l
V
SENSE(CM)
I
SENSE
V
RUN(TH)
V
RUN(HYS)
I
SS
UVLO
I
VOSNS+
I
VOSNS–
–0.5
±5
1
5.5
±50
4
1.3
V
nA
μA
V
mV
μA
V
SENSE(CM)
= 0.6V
V
SENSE(CM)
= 5V
V
RUN
Rising
l
1.1
1.2
80
1.0
3.4
3.65
4.2
±5
–15
4.0
4.5
±25
–50
V
V
nA
μA
3613fa
3
LTC3613
ELECTRICAL CHARACTERISTICS
SYMBOL
f
OSC
PARAMETER
Free Running Switching Frequency
Oscillator and Clock Synchronization
R
T
= 205k
R
T
= 80.6k
R
T
= 38.8k
175
450
900
2
0.5
6V < V
IN
< 24V
I
CC
= 0mA to 50mA
EXTV
CC
Rising
V
EXTVCC
= 5V. I
CC
= 50mA
V
FB
Rising (With Respect to Regulated
Feedback Voltage V
REG
)
V
FB
Falling (With Respect to Regulated
Feedback Voltage V
REG
)
V
FB
Returning
I
PGOOD
= 5mA
(Note 5)
5
–10
4.4
5.1
5.3
–1
4.6
200
200
7.5
–7.5
2
0.15
20
10
7.5
5.5
0.4
10
–5
5.55
–2
4.75
200
500
1000
225
550
1100
kHz
kHz
kHz
V
V
V
%
V
mV
mV
%
%
%
V
μs
μs
mohm
mohm
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. SV
IN
= 15V, V
FB
= V
OSNS+
– V
OSNS–
, unless otherwise noted. (Note 4)
CONDITIONS
MIN
TYP
MAX
UNITS
CLK
IH
CLK
IL
INTV
CC
INTV
CC(%)
EXTV
CC(TH)
EXTV
CC(HYS)
ΔINTV
CC
PGOOD Output
PGD
OV
PGD
UV
PGD
HYS
V
PGD(LO)
t
PGD(FALL)
t
PGD(RISE)
R
DS(ON)
R
DS(ON)
Clock Input High Level Into Mode/PLLIN
Clock Input Low Level Into Mode/PLLIN
Internal V
CC
Voltage
Internal V
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Switchover Hysteresis
EXTV
CC
Voltage Drop
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
Delay from OV/UV Fault to PGOOD Falling
Internal V
CC
Regulator and External V
CC
Delay from OV/UV Recovery to PGOOD Rising (Note 5)
Top Switch On-Resistance
Bottom Switch On-Resistance
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
T
J
is calculated from the ambient temperature, T
A
, and power
dissipation, P
D
, as follows:
T
J
= T
A
+ (P
D
• 29°C/W) (θ
JA
is simulated per JESD51-7 high effective
thermal conductivity test board)
θ
JC
=1°C/W (θ
JC
is simulated when heat sink is applied at the bottom
of the package.)
Note 3:
The LTC3613 is tested in a feedback loop that adjusts V
FB
= V
OSNS+
– V
OSNS–
to achieve a specified error amplifier output voltage (ITH).
Note 4:
The LTC3613 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3613E is guaranteed to meet specifications from
0°C to 125°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
LTC3613I is guaranteed over the full –40°C to 125°C operating junction
temperature range. 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
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