LT3693
36V, 3.5A, 2.4MHz
Step-Down Switching Regulator
FEATURES
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DESCRIPTIO
Wide Input Range: 3.6V to 36V
3.5A Maximum Output Current
Adjustable Switching Frequency: 200kHz to 2.4MHz
Low Shutdown Current: I
Q
< 1μA
Integrated Boost Diode
Synchronizable Between 250kHz to 2MHz
Power Good Flag
Saturating Switch Design: 95m On-Resistance
0.790V Feedback Reference Voltage
Output Voltage: 0.79V to 30V
Thermal Protection
Soft-Start Capability
Small 10-Pin Thermally Enhanced MSOP and
(3mm
×
3mm) DFN Packages
The LT
®
3693 is an adjustable frequency (200kHz to
2.4MHz) monolithic buck switching regulator that accepts
input voltages up to 36V. A high efficiency 95m switch
is included on the die along with a boost Schottky diode
and the necessary oscillator, control, and logic circuitry.
Current mode topology is used for fast transient response
and good loop stability. Shutdown reduces input supply
current to less than 1μA while a resistor and capacitor on
the RUN/SS pin provide a controlled output voltage ramp
(soft-start). A power good flag signals when V
OUT
reaches
91% of the programmed output voltage. The LT3693 is
available in 10-Pin MSOP and 3mm
×
3mm DFN packages
with exposed pads for low thermal resistance.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
APPLICATIO S
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Automotive Battery Regulation
Power for Portable Products
Distributed Supply Regulation
Industrial Supplies
Wall Transformer Regulation
TYPICAL APPLICATIO
V
IN
6.3V TO 36V
V
IN
OFF ON
15k
10
m
F
680pF
V
C
RT
PG
63.4k
SYNC
RUN/SS
5V Step-Down Converter
V
OUT
5V
3.5A
BD
EFFICIENCY (%)
BOOST
0.47
m
F 4.7
m
H
LT3693
SW
100
536k
GND
FB
100k
47
m
F
3693 TA01a
U
Efficiency
V
IN
= 12V
90
V
IN
= 34V
80
V
IN
= 24V
70
60
V
OUT
= 5V
L = 4.7μH
f = 600kHz
0
0.5
2
1.5
1
2.5
OUTPUT CURRENT (A)
3
3.5
3693 G01
U
U
50
3693f
1
LT3693
ABSOLUTE
AXI U RATI GS
V
IN
, RUN/SS Voltage .................................................36V
BOOST Pin Voltage ...................................................56V
BOOST Pin Above SW Pin.........................................30V
FB, RT, V
C
Voltage .......................................................5V
PG, BD Voltage .........................................................30V
SYNC Voltage ............................................................20V
PIN CONFIGURATION
TOP VIEW
BD
BOOST
SW
V
IN
RUN/SS
1
2
3
4
5
11
10 RT
9 V
C
8 FB
7 PG
6 SYNC
TOP VIEW
BD
BOOST
SW
V
IN
RUN/SS
1
2
3
4
5
10
9
8
7
6
RT
V
C
FB
PG
SYNC
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3693EDD#PBF
LT3693IDD#PBF
LT3693EMSE#PBF
LT3693IMSE#PBF
TAPE AND REEL
LT3693EDD#TRPBF
LT3693IDD#TRPBF
LT3693EMSE#TRPBF
LT3693IMSE#TRPBF
PART MARKING*
LDGB
LDGB
LTDFZ
LTDFZ
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead Plastic MSOP
10-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–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
PARAMETER
Minimum Input Voltage
Quiescent Current from V
IN
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
RUN/SS
= 10V, V
BOOST
= 15V, V
BD
= 3.3V unless otherwise
noted. (Note 2)
CONDITIONS
●
V
RUN/SS
= 0.2V
V
BD
= 3V, Not Switching
V
BD
= 0, Not Switching
●
Quiescent Current from BD
V
RUN/SS
= 0.2V
V
BD
= 3V, Not Switching
●
2
U
W W
W
(Note 1)
Operating Junction Temperature Range (Note 2)
LT3693E............................................. –40°C to 125°C
LT3693I.............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
(MSE Only) ....................................................... 300°C
11
MSE PACKAGE
10-LEAD PLASTIC MSOP
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
MIN
TYP
3
0.01
0.45
1.3
0.01
0.9
MAX
3.6
0.5
1.2
2.3
0.5
1.8
UNITS
V
μA
mA
mA
μA
mA
3693f
LT3693
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Bias Voltage (BD Pin)
Feedback Voltage
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
RUN/SS
= 10V, V
BOOST
= 15V, V
BD
= 3.3V unless otherwise
noted. (Note 2)
CONDITIONS
V
BD
= 0, Not Switching
780
775
MIN
TYP
1
2.7
790
790
10
0.002
525
2000
60
60
5.3
2.0
R
T
= 8.66k
R
T
= 29.4k
R
T
= 187k
●
MAX
10
3
800
805
40
0.01
UNITS
μA
V
mV
mV
nA
%/V
μMho
μA
μA
A/V
V
FB Pin Bias Current (Note 3)
FB Voltage Line Regulation
Error Amp g
m
Error Amp Gain
V
C
Source Current
V
C
Sink Current
V
C
Pin to Switch Current Gain
V
C
Clamp Voltage
Switching Frequency
V
FB
= 0.8V, V
C
= 0.4V
4V < V
IN
< 36V
●
2.2
1.0
200
4.6
2.45
1.1
230
60
5.4
335
0.02
2.7
1.25
260
150
6.0
2
2.0
60
8
2.5
MHz
MHz
kHz
nS
A
mV
μA
V
mA
μA
V
V
mV
mV
Minimum Switch Off-Time
Switch Current Limit
Switch V
CESAT
Boost Schottky Reverse Leakage
Minimum Boost Voltage (Note 4)
BOOST Pin Current
RUN/SS Pin Current
RUN/SS Input Voltage High
RUN/SS Input Voltage Low
PG Threshold Offset from Feedback Voltage
PG Hysteresis
PG Leakage
PG Sink Current
SYNC Low Threshold
SYNC High Threshold
SYNC Pin Bias Current
V
SYNC
= 0V
V
PG
= 5V
V
PG
= 0.4V
V
FB
Rising
I
SW
= 1A
V
RUN/SS
= 2.5V
Duty Cycle = 5%
I
SW
= 3.5A
V
SW
= 10V, V
BD
= 0V
●
1.5
35
5
0.2
65
10
0.1
1
μA
μA
V
●
200
0.5
800
0.8
0.1
V
μA
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 LT3693E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the –40°C to 125°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3693I specifications are
guaranteed over the –40°C to 125°C temperature range.
Note 3:
Bias current flows out of the FB pin.
Note 4:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
3693f
3
LT3693
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency
100
V
IN
= 12V
90
EFFICIENCY (%)
EFFICIENCY (%)
V
IN
= 34V
80
V
IN
= 24V
90
100
80
V
IN
= 34V
V
IN
= 24V
EFFICIENCY (%)
70
60
V
OUT
= 5V
L = 4.7μH
f = 600kHz
0
0.5
2
1.5
1
2.5
OUTPUT CURRENT (A)
3
3.5
3693 G01
50
Maximum Load Current
5.5
5.0
LOAD CURRENT (A)
4.5
MINIMUM
4.0
3.5
3.0
2.5
5
10
15
20
25
INPUT VOLTAGE (V)
30
3693 G06
TYPICAL
SWITCH CURRENT LIMIT(A)
5.0
LOAD CURRENT (A)
TYPICAL
5.5
5.0
4.5
4.0
3.5
3.0
5
10
25
20
15
INPUT VOLTAGE (V)
30
3693 G07
V
OUT
= 3.3V
T
A
= 25°C
L = 4.7μH
f = 600kHz
Switch Current Limit
6.5
6.0
SWITCH CURRENT LIMIT (A)
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G09
BOOST PIN CURRENT (mA)
DUTY CYCLE = 10 %
VOLTAGE DROP (mV)
500
400
300
200
100
0
0
1
3
2
4
SWITCH CURRENT (A)
5
3693 G10
DUTY CYCLE = 90 %
4
U W
T
A
= 25°C unless otherwise noted.
Efficiency
100
3.0
Efficiency
V
IN
= 12V
90
2.5
TOTAL POWER LOSS (W)
80
2.0
70
70
V
IN
= 12V
V
OUT
= 5V
L = 4.7μH
f = 600kHz
0
0.5
2
1.5
1
2.5
OUTPUT CURRENT (A)
3
3.5
3693 G03
1.5
60
V
OUT
= 3.3V
L = 3.3μH
f = 600kHz
0
0.5
2
1.5
1
2.5
OUTPUT CURRENT (A)
3
3.5
3693 G02
60
1.0
50
50
0.5
Maximum Load Current
5.5
6.0
Switch Current Limit
4.5
MINIMUM
4.0
V
OUT
= 5V
T
A
= 25°C
L = 4.7μH
f = 600kHz
3.5
3.0
0
20
60
40
DUTY CYCLE (%)
80
100
3693 G08
Switch Voltage Drop
700
600
120
105
90
75
60
45
30
15
0
Boost Pin Current
0
1
2
3
SWITCH CURRENT (A)
4
5
3693 G11
3693f
LT3693
TYPICAL PERFOR A CE CHARACTERISTICS
Feedback Voltage
840
1.20
R
T
= 34.0k
1.15
FREQUENCY (MHz)
820
1.10
1.05
1.00
0.95
0.90
0.85
760
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G12
SWITCHING FREQUENCY (kHz)
FEEDBACK VOLTAGE (mV)
800
780
Minimum Switch On-Time
140
MINIMUM SWITCH ON TIME (ns)
120
SWITCH CURRENT LIMIT (A)
100
80
60
40
20
0
–50 –25
7
6
5
4
3
2
1
0
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G15
RUN/SS PIN CURRENT (μA)
Boost Diode
1.4
1.2
BOOST DIODE V
F
(V)
V
C
PIN CURRENT (μA)
1.0
0.8
0.6
0.4
0.2
0
0
0.5
1.0
1.5
BOOST DIODE CURRENT (A)
2.0
3693 G18
INPUT VOLTAGE (V)
U W
T
A
= 25°C unless otherwise noted.
Frequency Foldback
1200
R
T
= 34.0k
1000
800
600
400
200
0
Switching Frequency
0.80
–50 –25
0
25 50 75 100 125 150
TEMPERATURE ( C)
3693 G13
0
100 200 300 400 500 600 700 800 900
FB PIN VOLTAGE (mV)
3693 G14
Soft-Start
12
10
8
6
4
2
0
0
0.5
2.5
2
1.5
RUN/SS PIN VOLTAGE (V)
1
3
3.5
3693 G16
RUN/SS Pin Current
0
5
20
30
15
25
10
RUN/SS PIN VOLTAGE (V)
35
3693 G17
Error Amp Output Current
50
40
30
20
10
0
–10
–20
–30
–40
–50
–200
2.0
–100
100
0
FB PIN ERROR VOLTAGE (mV)
200
3693 G19
Minimum Input Voltage
5.0
4.5
4.0
3.5
3.0
2.5
V
OUT
= 3.3V
T
A
= 25 C
L = 4.7 H
f = 600kHz
1
10
100
1000
LOAD CURRENT (mA)
10000
3693 G20
3693f
5
FPGA/CPLD
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