nous step-down DC/DC converter utilizing a constant
frequency, average current mode control architecture. It
operates from an input voltage range of 4.4V to 105V and
provides an adjustable regulated output voltage from 1V
to V
IN
while delivering up to 2.3A of output current.
The LTC7103 features high frequency operation and a low
minimum on-time that reduce inductor size and enable
constant-frequency operation even at very high step-
down ratios. In addition, the LTC7103 achieves the low-
est possible dropout voltage with 100% maximum duty
cycle operation. During light load operation, converter
efficiency and output ripple can be optimized by selecting
Burst Mode or pulse-skipping operation.
The LTC7103 includes accurate, high speed average cur-
rent programming and monitoring without the need for
an external sense resistor. Additional features include a
bypass LDO to maximize efficiency, fixed or adjustable
output voltage and loop compensation, and a wide array
of protection features to enhance reliability.
All registered trademarks and trademarks are the property of their respective owners.
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Wide V
IN
Range: 4.4V to 105V (110V Abs Max)
Ultralow EMI/EMC Emissions: CISPR 25 Compliant
2µA I
Q
When Regulating 48V
IN
to 3.3V
OUT
Fast and Accurate Output Current Programming and
Monitoring with No External R
SENSE
Brick Wall Current Limit
Low Minimum On-Time: 40ns
Wide V
OUT
Range: 1V to V
IN
100% Maximum Duty Cycle Operation
Programmable Fixed Frequency: 200kHz to 2MHz
Eight, Pin-Selectable Fixed (1.2V to 15V) or
Adjustable Output Voltages
Selectable Pulse-Skipping or Low Ripple Burst
Mode
®
Operation at Light Loads
PLL Synchronization to External Clock
EXTV
CC
LDO Powers Chip from V
OUT
= 3.3V to 40V
OPTI-LOOP
®
or Fixed Internal Compensation
Input and Output Overvoltage Protection
Thermally Enhanced (5mm × 6mm) QFN Package
APPLICATIONS
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Battery Chargers and CC/CV Supplies
Automotive and Military Systems
Industrial, Avionics and Heavy Equipment
Medical Instruments and Telecommunication
Systems
TYPICAL APPLICATION
5V to 105V Input to 5V/2.3A Output Step-Down Regulator
V
IN
5V TO 105V
4.7µF
RUN
I
CTRL
OVLO
V
PRG2
PLLIN/MODE
FREQ
SGND
PGND
7103 TA01a
Efficiency vs Load Current
100
95
V
OUT
= 5V
V
IN
LTC7103
BOOST
0.1µF
SW
V
FB
EXTV
CC
I
MON
I
TH
INTV
CC
1µF
CURRENT
MONITOR
EFFICIENCY (%)
18µH
V
OUT
5V
2.3A
100µF
90
85
80
75
70
65
60
55
50
0.1
1
f
SW
= 300kHz
FIGURE 14 CIRCUIT
V
IN
= 12V
V
IN
= 24V
V
IN
= 48V
V
IN
= 72V
10
100
LOAD CURRENT (mA)
1000
7103 TA01b
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1
Rev. A
LTC7103
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
Supply Voltage ....................................–0.3V to 110V
INTV
CC
, (BOOST-SW) Voltages .................... –0.3V to 6V
BOOST Voltage .........................................–0.3V to 110V
RUN Voltage..............................................–0.3V to 110V
V
FB
, PGOOD Voltages ................................ –0.3V to 16V
EXTV
CC
Voltage ..........................................–0.3V to 41V
R
IND
, V
PRG1
, V
PRG2
Voltages ................. –0.3V to INTV
CC
I
CTRL
, SS Voltages ................................ –0.3V to INTV
CC
FREQ, I
TH
, PLLIN/MODE, OVLO Voltages..... –0.3V to 6V
Operating Junction Temperature Range (Notes 2, 3, 4)
LTC7103E, LTC7103I .......................... –40°C to 125°C
LTC7103H .......................................... –40°C to 150°C
LTC7103MP ....................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
PGND
PGND
V
IN
V
IN
V
IN
27 BOOST
RUN 3
26 SW
25 SW
SGND 6
OVLO 7
R
IND
8
I
TH
9
V
FB
10
11 12 13 14 15 16 17 18
PLLIN/MODE
FREQ
CLKOUT
PGOOD
SS
I
MON
V
PRG1
I
CTRL
21 INTV
CC
20 EXTV
CC
19 V
PRG2
PGND
37
24 SW
36 35
32 31 30
UHE36(26) PACKAGE
36-LEAD (5mm
×
6mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 37) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC7103EUHE#PBF
LTC7103IUHE#PBF
LTC7103HUHE#PBF
LTC7103MPUHE#PBF
TAPE AND REEL
LTC7103EUHE#TRPBF
LTC7103IUHE#TRPBF
LTC7103HUHE#TRPBF
LTC7103MPUHE#TRPBF
PART MARKING*
7103
7103
7103
7103
PACKAGE DESCRIPTION
36-Lead (5mm × 6mm) Plastic QFN
36-Lead (5mm × 6mm) Plastic QFN
36-Lead (5mm × 6mm) Plastic QFN
36-Lead (5mm × 6mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications.
Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
2
Rev. A
For more information
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LTC7103
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
IN(UVLO)
V
OUT
I
Q
PARAMETER
Operating Input Voltage Range
V
IN
Undervoltage Lockout
Operating Output Voltage Range
V
IN
Input DC Supply Current
Pulse-Skipping Mode
Sleep Mode
Shutdown
V
IN
Input Current In Regulation
V
FB
Regulated Feedback Voltage
V
IN
Rising
V
IN
Falling
(Note 9)
(Note 8)
V
FB
= 1.04V, EXTV
CC
= 3.3V
V
FB
= 1.04V, EXTV
CC
= 0V
V
FB
= 1.04V, EXTV
CC
= 3.3V
V
FB
= 1.04V, EXTV
CC
= 0V
RUN = 0V
Figure 14 Circuit, V
IN
= 48V, I
OUT
= 500μA
Figure 16 Circuit, V
IN
= 48V, I
OUT
= 0μA
(Note 5)
I
TH
Voltage = 0.5V to 1.2V, V
IN
= 4.5V to 105V
V
PRG1
= V
PRG2
= FLOAT
V
PRG1
= V
PRG2
= INTV
CC
V
PRG1
= FLOAT, V
PRG2
= INTV
CC
V
PRG1
= V
PRG2
= SGND
V
PRG1
= SGND, V
PRG2
= FLOAT
V
PRG1
= SGND, V
PRG2
= INTV
CC
V
PRG1
= FLOAT, V
PRG2
= SGND
V
PRG1
= INTV
CC
, V
PRG2
= FLOAT
V
PRG1
= INTV
CC
, V
PRG2
= SGND
V
PRG1
= V
PRG2
= FLOAT
V
PRG1
or V
PRG2
Tied to SGND or INTV
CC
I
TH
= 1V, Sink/Source = 5µA (Note 5)
(Note 7)
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
= 12V unless otherwise noted.
CONDITIONS
MIN
4.4
4.36
4.11
1.0
200
4.4
1.0
9.0
0.7
64
2
8.0
75
4.50
4.25
TYP
MAX
105
4.64
4.39
105
UNITS
V
V
V
V
µA
mA
µA
µA
µA
µA
µA
Main Regulator and Voltage Loop
l
l
l
l
l
l
l
l
l
0.990
1.182
1.770
2.455
3.234
3.528
4.900
11.75
14.70
1.000
1.200
1.800
2.500
3.300
3.600
5.000
12.00
15.00
±2
1.25
1.52
40
265
142
1.010
1.218
1.827
2.537
3.350
3.654
5.075
12.24
15.30
±10
1.6
60
V
V
V
V
V
V
V
V
V
nA
µA
mS
ns
mΩ
mΩ
Feedback Input Bias Current
g
m
t
ON,MIN
Error Amplifier g
m
Minimum Controllable ON-Time
R
DS(ON)TOP
Top Switch On-Resistance
R
DS(ON)BOT
Bottom Switch On-Resistance
Current Control and Monitoring
I
LIM(AVG)
I
PK
V
IMON
Average Output Current Limit
(Note 6)
I
CTRL
= 1.3V
I
CTRL
= 0.58V
I
CTRL
= 1.3V
I
CTRL
= 0.58V
(Note 6)
I
SW
= 2A
I
SW
= 0.5A
V
ICTRL
= 0.5V
SS = 0V
SS = FLOAT
Relative to Regulated V
FB
V
RUN
Rising
V
RUN
Falling
RUN = 1.5V
V
OVLO
Rising
l
l
l
l
2.25
0.36
3.32
1.56
1.04
0.54
18
8
7
1.16
1.06
–10
1.16
2.50
0.5
3.70
1.70
1.12
0.58
20
11
1.2
10
1.21
1.11
100
0
1.21
2.75
0.64
4.30
2.09
1.19
0.63
22
14
13
1.26
1.16
10
1.26
A
A
A
A
V
V
µA
µA
ms
%
V
V
mV
nA
V
Top Switch Peak Current Limit
Current Monitor Output Voltage
I
CTRL
Pin Pull-Up Current
Start-Up and Shutdown
I
SS
t
SS(INT)
V
FB(OV)
V
RUN(ON)
Soft-Start Charge Current
Internal Soft-Start Ramp Time
Feedback Overvoltage Protection
RUN Pin ON Threshold
RUN Pin Hysteresis
RUN Pin Leakage Current
V
OV(R)
OVLO Pin Rising Threshold
l
For more information
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3
Rev. A
LTC7103
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
OVLO Pin Hysteresis
OVLO Pin Leakage Current
Bias Regulators and Housekeeping
INTV
CC
Undervoltage Lockout
V
EXTVCC
EXTV
CC
Switchover Voltage
Regulated INTV
CC
Voltage from V
IN
Regulated INTV
CC
Voltage from EXTV
CC
Oscillator and Phase-Locked Loop
Programmable Frequency Accuracy
f
LOW
f
HIGH
Low Preset Frequency
High Preset Frequency
Synchronizable Frequency
PLLIN/MODE Input High Level for Clocking
PLLIN/MODE Input Low Level for Clocking
PGOOD Output
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
I
PGOOD
= 1mA
V
PGOOD
= 12V
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Positive
Hysteresis
V
FB
Ramping Negative
Hysteresis
T
PG
Delay for Reporting a Fault
–13
7
10
2.5
–10
2.5
24
–7
13
%
%
%
%
µs
–1
0.3
0.5
1
V
µA
R
FREQ
= 12.5k (200kHz) to 57.5k (2MHz)
PLLIN/MODE = 0V
V
FREQ
= 0V;
PLLIN/MODE = 0V
V
FREQ
= INTV
CC
;
PLLIN/MODE = 0V
PLLIN/MODE = External Clock
PLLIN/MODE = External Clock
PLLIN/MODE = External Clock
l
l
l
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
= 12V unless otherwise noted.
CONDITIONS
OVLO = 1.5V
INTV
CC
Rising
INTV
CC
Falling
EXTV
CC
Rising
EXTV
CC
Falling
l
l
MIN
–10
TYP
65
0
3.00
2.80
MAX
10
UNITS
mV
nA
V
V
3.04
2.95
3.37
3.37
–15
270
0.9
200
2.0
3.10
3.00
3.5
3.5
3.17
3.07
3.6
3.6
15
V
V
V
V
%
kHz
MHz
kHz
V
V
300
1.0
330
1.1
2000
0.8
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 LTC7103E is guaranteed to meet specifications from 0°C
to 85°C with specifications over the –40°C to 125°C operating junction
temperature range assured by design, characterization and correlation with
statistical process controls. The LTC7103I is guaranteed over the –40°C to
125°C operating junction temperature range, the LTC7103H is guaranteed
over the –40°C to 150°C operating junction temperature range, and the
LTC7103MP is tested and guaranteed over the –55°C to 150°C operating
junction temperature range. High junction temperatures degrade operating
lifetimes; operating lifetime is derated for junction temperatures 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.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
=
T
A
+ (P
D
•
θ
JA
°C/W)
Note 4:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device. The overtemperature protection level is not production tested.
Note 5:
The LTC7103 is tested in a feedback loop that servos V
FB
to a
voltage near the internal reference voltage to obtain the specified I
TH
voltage.
Note 6:
The Average Output Current Limit, the Top Switch Peak Current
Limit and the Current Monitor Output Voltage are measured in a test circuit
that simulates operation in a typical application.
Note 7:
The minimum controllable on-time is measured in a test mode.
(See Minimum ON-Time Considerations in the Applications Information
section.)
Note 8:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 9:
See Operating at V
OUT
> 6V in the Applications Information section
for details about additional design constraints that may apply.
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