monolithic synchronous buck regulator using a controlled
on-time current mode architecture, with phase lockable
switching frequency. The operating supply voltage range is
from 3.1V to 20V, making it suitable for lithium-ion battery
stacks as well as point of load power supply applications
from a 12V or 5V input.
The operating frequency is programmable from 500kHz to
4MHz with an external resistor and may be synchronized
to an external clock signal. The high frequency capability
allows the use of small surface mount inductors and
capacitors. The unique constant frequency/controlled
on-time architecture is ideal for high step-down ratio ap-
plications that operate at high frequency while demanding
fast transient response.
The LTC3636/LTC3636-1 can select between forced con-
tinuous mode and high efficiency Burst Mode operation.
The LTC3636 and LTC3636-1 differ in their output voltage
sense range.
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. Patents including 5481178, 5847554, 6580258, 6304066, 6476589, 6774611.
n
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Wide V
IN
Range: 3.1V to 20V
Wide V
OUT
Range:
0.6V to 5V (LTC3636)
1.8V to 12V (LTC3636-1)
Output Current per Channel: 6A
High Efficiency: Up to 95%
Die Temperature Monitor
Adjustable Switching Frequency: 500kHz to 4MHz
External Frequency Synchronization
Current Mode Operation for Excellent Line and
Load Transient Response
0.6V Reference Allows Low Output Voltages
User Selectable Burst Mode
®
Operation or Forced
Continuous Operation
Output Voltage Tracking and Soft-Start Capability
Short-Circuit Protected
Overvoltage Input and Overtemperature Protection
Power Good Status Outputs
Low Profile 4mm
×
5mm 28-Lead QFN Package
APPLICATIONS
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Distributed Power Systems
Battery-Powered Instruments
Point-of-Load Power Supplies
TYPICAL APPLICATION
V
IN
10V TO 20V
47µF
x2
RUN1
RUN2
V
IN2
V
IN1
Efficiency vs Load Current
INTV
CC
ITH1
ITH2
RT
100
4.7µF
97
94
EFFICIENCY (%)
91
88
85
82
79
76
73
70
3636 TA01a
LTC3636/
LTC3636-1
f
SW
= 2MHz
V
IN
= 12V
TMON
TRACKSS2
PGOOD2
BOOST2
MODE/SYNC
TRACKSS1
PGOOD1
BOOST1
0.1µF
0.56µH
V
OUT1
3.3V AT 6A
0.1µF
V
OUT2
5V AT 6A
0.56µH
47µF
22pF
SW2
73.2k
V
FB2
10k
GND
SW1
45.3k
V
FB1
10k
47µF
22pF
V
OUT
= 5V
V
OUT
= 3.3V
0
0.6 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 6.0
LOAD CURRENT (A)
3636 TA01b
3636fb
For more information
www.linear.com/LTC3636
1
LTC3636/LTC3636-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
TRACKSS1
PGOOD1
BOOST1
22 V
IN1
21 V
IN1
20 SW1
GND
GND
SW2
V
IN2
V
IN2
BOOST2
V
IN1
, V
IN2
................................................... –0.3V to 22V
PGOOD1, PGOOD2..................................... –0.3V to 22V
BOOST1-SW1, BOOST2-SW2 ................... –0.3V to 3.6V
TRACKSS1, TRACKSS2 ............................ –0.3V to 3.6V
ITH1, ITH2, RT, MODE/SYNC ........ –0.3V to INTV
CC
+ 0.3V
V
FB1
, V
FB2
, TMON. ...................... –0.3V to INTV
CC
+ 0.3V
RUN1, RUN2 .............................................. –0.3V to 22V
Operating Junction Temperature Range
(Notes 3, 4) ............................................ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
28 27 26 25 24 23
ITH1 1
RUN1 2
MODE/SYNC 3
RT 4
INTV
CC
5
TMON 6
RUN2 7
ITH2 8
30
GNDT
33
SW1T
19
32
GNDT 18
29
17
INTV
CCT
31
34
GNDT SW2T 16
15
9 10 11 12 13 14
PGOOD2
TRACKSS2
SW2
V
FB2
GND
UFD PACKAGE
VARIATION: AA
28-LEAD (4mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 21°C/W,
θ
JC
= 7°C/W
θ
JA
DERIVED FROM 6-LAYER PCB DC2335 DEMO BOARD
ORDER INFORMATION
LEAD FREE FINISH
LTC3636IUFD#PBF
LTC3636EUFD#PBF
LTC3636IUFD-1#PBF
LTC3636EUFD-1#PBF
TAPE AND REEL
LTC3636IUFD#TRPBF
LTC3636EUFD#TRPBF
http://www.linear.com/product/LTC3636#orderinfo
PART MARKING*
3636
3636
36361
36361
PACKAGE DESCRIPTION
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
LTC3636IUFD-1#TRPBF
LTC3636EUFD-1#TRPBF
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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
Selection Table
PART NUMBER
LTC3636
LTC3636-1
V
OUT
SENSE RANGE
0.6V to 5V
1.8V to 12V
SW1
V
FB1
GND
2
3636fb
For more information
www.linear.com/LTC3636
LTC3636/LTC3636-1
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
J
= 25°C (Note 2). V
IN1
= V
IN2
= 12V unless otherwise noted.
SYMBOL
V
IN1
PARAMETER
Supply Range
V
IN1
Supply Range
V
IN2
Supply Range
Output Voltage Range (Note 4)
I
Q
Input DC Supply Current (V
IN1
+ V
IN2
)
Both Channels Active (Note 5)
Sleep Current
Shutdown
Feedback Reference Voltage
Reference Voltage Line Regulation
Output Voltage Load Regulation
Feedback Pin Input Current
Error Amplifier Transconductance
Minimum On Time
Minimum Off Time
Oscillator Frequency
V
RT
= INTV
CC
RT = 162k
RT = 80.6k
ITH = 1.8V
1.4
1.7
3.4
6
ITH = 1.2V
LTC3636
LTC3636-1
1.8
30
30
100
2
2
4
6.6
–4.2
32
18
V
IN
= 20V, V
RUN
= 0V
T
A
= 25°C
V
IN
Rising
V
IN
Falling
3.6V < V
IN
< 20V, 0mA Load
0mA to 50mA Load, V
IN
= 4V to 20V
INTV
CC
Rising, V
IN
= INTV
CC
INTV
CC
Falling, V
IN
= INTV
CC
l
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
l
l
l
MIN
3.1
3.1
1.5
0.6
1.8
TYP
MAX
20
20
20
5
12
UNITS
V
V
V
V
V
mA
µA
µA
3.1V < V
IN1
< 20V
LTC3636
LTC3636-1
MODE = 0V
MODE = INTV
CC
, V
FB1
, V
FB2
> 0.6
RUN1 = RUN2 = 0V
1.3
600
13
l
V
FB
∆V
LINE_REG
∆V
LOAD_REG
I
FB
g
m(EA)
t
ON
t
OFF
f
OSC
I
LIM
R
DS(ON)
I
SW(LKG)
0.594
0.6
0.002
0.05
0.606
V
%/V
%
V
IN
= 3.1V to 20V
ITH = 0.8V to 1.6V
±30
35
nA
mS
ns
ns
2.6
2.3
4.6
7.2
MHz
MHz
MHz
A
A
mΩ
mΩ
Valley Switch Current Limit
Negative Valley Switch Current Limit
Top Switch On-Resistance
Bottom Switch On-Resistance
Switch Leakage Current
Internal Temperature Monitor
Internal Temperature Monitor Slope (Note 6)
0.01
1.5
200
20.3
3.1
22.5
21.5
3.3
1.3
2.7
2.55
1.16
0.96
1.22
1.01
0
8
–8
–3
3
–5
5
±1
µA
V
°C/V
V
V
V
%
V
V
V
V
µA
%
%
%
%
V
VIN-OV
V
IN
Overvoltage Lockout Threshold
INTV
CC
Voltage
INTV
CC
Load Regulation
INTV
CC
Undervoltage Lockout Threshold
RUN Threshold Rising
RUN Threshold Falling
RUN Leakage Current
PGOOD Good-to-Bad Threshold
PGOOD Bad-to-Good Threshold
22.5
3.5
2.9
1.28
1.06
±3
10
–10
V
FB
Rising
V
FB
Falling
V
FB
Rising
V
FB
Falling
3636fb
For more information
www.linear.com/LTC3636
3
LTC3636/LTC3636-1
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
J
= 25°C (Note 2). V
IN1
= V
IN2
= 12V unless otherwise noted.
SYMBOL
R
PGOOD
t
PGOOD
t
SS
I
TRACKSS
V
MODE/SYNC
PARAMETER
PGOOD Pull-Down Resistance
Power Good Filter Time
Internal Soft-Start Time
V
FB
During Tracking
TRACKSS Pull-Up Current
MODE/SYNC Threshold Voltage
SYNC Threshold Voltage
I
MODE
MODE/SYNC Input Current
MODE V
IH
MODE V
IL
SYNC V
IH
MODE = 0V
MODE = INTV
CC
1
0.95
1.5
–1.5
10% to 90% Rise Time
TRACKSS = 0.3V
0.28
CONDITIONS
10mA Load
20
MIN
TYP
25
40
1000
0.3
1.4
0.4
1500
0.315
MAX
UNITS
Ω
µs
µs
V
µA
V
V
V
µA
µA
ELECTRICAL CHARACTERISTICS
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 LTC3636 is tested under pulsed load conditions such
that T
J
≈ T
A
. The LTC3636E 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
LTC3636I is guaranteed over the –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
impedance and other environmental factors. The junction temperature
(T
J
, in °C) is calculated from the ambient temperature (T
A
, in °C) and
power dissipation (P
D
, in Watts) according to the formula:
T
J
= T
A
+ (P
D
•
θ
JA
), where
θ
JA
(in °C/W) is the package thermal
impedance.
Note 3:
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.
Note 4:
Output voltages outside the specified range are not optimized for
controlled on-time operation. Refer to the Applications Information section
for further discussions related to the output voltage range.
Note 5:
Dynamic supply current is higher due to the internal gate charge
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