LT1107
Micropower
DC/DC Converter
Adjustable and Fixed 5V, 12V
FEATURES
s
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DESCRIPTIO
Operates at Supply Voltages from 2V to 30V
Consumes Only 320µA Supply Current
Works in Step-Up or Step-Down Mode
Only Three External Components Required
Low-Battery Detector Comparator On-Chip
User Adjustable Current Limit
Internal 1A Power Switch
Fixed or Adjustable Output Voltage Versions
Space Saving 8-Pin MiniDIP or SO-8 Package
The LT
®
1107 is a versatile micropower DC/DC converter.
The device requires only three external components to
deliver a fixed output of 5V or 12V. Supply voltage ranges
from 2V to 12V in step-up mode and to 30V in step-down
mode. The LT1107 functions equally well in step-up, step-
down, or inverting applications.
The LT1107 is pin-for-pin compatible with the LT1111, but
has a duty cycle of 70%, resulting in increased output
current in many applications. The LT1107 can deliver
150mA at 5V from a 2AA cell input and 5V at 300mA from
24V in step-down mode. Quiescent current is just 320µA,
making the LT1107 ideal for power-conscious battery-
operated systems. The 63kHz oscillator is optimized to
work with surface mount inductors and capacitors.
Switch current limit can be programmed with a single
resistor. An auxiliary gain block can be configured as a
low-battery detector, linear post regulator, undervoltage
lock-out circuit, or error amplifier.
, LTC and LT are registered trademarks of Linear Technology Corporation
APPLICATIO S
s
s
s
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Palmtop Computers
3V to 5V, 5V to 12V Converters
24V to 5V, 12V to 5V Converters
LCD Bias Generators
Peripherals and Add-On Cards
Battery Backup Supplies
Cellular Telephones
Portable Instruments
TYPICAL APPLICATIO
Palmtop Computer Logic Supply
L1*
33µH
MBRS120T3
5V
150mA
82
80
78
V
IN
= 3V
47Ω
EFFICIENCY (%)
76
74
72
70
68
66
I
LIM
2
×
AA
ALKALINE
CELLS
V
IN
SW1
+
47µF
LT1107-5
+
100µF
SENSE
GND
SW2
* SUMIDA CD54-330K
COILCRAFT DT3316-473
64
1107 TA01
U
Efficiency
V
IN
= 2V
V
IN
= 2.5V
1
10
100
LOAD CURRENT (mA)
400
1107 TA02
U
U
1107fa
1
LT1107
ABSOLUTE
AXI U
RATI GS
Supply Voltage (V
IN
) ............................................... 36V
SW1 Pin Voltage (V
SW1
) ......................................... 50V
SW2 Pin Voltage (V
SW2
) ............................ – 0.5V to V
IN
Feedback Pin Voltage (LT1107) ................................ 5V
Sense Pin Voltage (LT1107-5, LT1107-12) ............ 36V
Maximum Power Dissipation ............................ 500mW
Set Pin Voltage ...................................................... 5.5V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
I
LIM
1
V
IN
2
SW1 3
SW2 4
8
7
6
5
FB (SENSE)*
SET
AO
GND
ORDER PART
NUMBER
LT1107CN8
LT1107CN8-5
LT1107CN8-12
TOP VIEW
I
LIM
1
V
IN
2
SW1 3
SW2 4
8 FB(SENSE)*
7 SET
6 AO
5 GND
N8 PACKAGE
8-LEAD PLASTIC DIP
* FIXED VERSIONS
T
JMAX
= 90°C,
θ
JA
= 130°C/W (N)
J8 PACKAGE
8-LEAD CERAMIC DIP
T
JMAX
= 150°C,
θ
JA
= 120°C/W (J)
LT1107MJ8
LT1107MJ8-5
LT1107MJ8-12
OBSOLETE PACKAGE
Consider the N8 Package for Alternate Source
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
PARAMETER
Quiescent Current
Quiescent Current, Step-Up Mode Configuration
V
IN
Input Voltage
Comparator Trip Point Voltage
V
OUT
Output Sense Voltage
Comparator Hysteresis
Output Hysteresis
f
OSC
t
ON
Oscillator Frequency
Duty Cycle, Step-Up Mode
Switch ON Time, Step-Up Mode
The
q
denotes the specifications which apply over the full operating
temperature range, V
IN
= 3V, military or commercial version, T
A
= 25°C, unless otherwise noted.
CONDITIONS
Switch OFF
No Load
Step-Up Mode
Step-Down Mode
LT1107 (Note 2)
LT1107-5 (Note 3)
LT1107-12 (Note 3)
LT1107
LT1107-5
LT1107-12
Full Load
I
LIM
Tied to V
IN
LT1107-5
LT1107-12
q
q
q
q
q
q
q
q
2
U
U
W
W W
U
W
(Note 1)
Maximum Switch Current ...................................... 1.5A
Operating Temperature Range
LT1107C ................................................ 0°C to 70°C
LT1107I ............................................ –45°C to 85°C
LT1107M(OBSOLETE)
...............
– 55°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LT1107CS8
LT1107CS8-5
LT1107CS8-12
LT1107IS8
S8 PART MARKING
1107
11075
110712
1107I
S8 PACKAGE
8-LEAD PLASTIC SO
*FIXED VERSIONS
T
JMAX
= 90°C,
θ
JA
= 150°C/W
MIN
TYP
320
360
550
MAX
450
UNITS
µA
µA
µA
2
1.2
4.75
11.40
1.25
5
12
8
32
75
50
64
8.8
63
70
11
12.6
30.0
1.3
5.25
12.60
12.5
50
120
77
76
12.7
V
V
V
V
V
mV
mV
mV
kHz
%
µs
1107fa
LT1107
The
q
denotes the specifications which apply over the full operating
temperature range, V
IN
= 3V, military or commercial version, T
A
= 25°C, unless otherwise noted.
SYMBOL
PARAMETER
Feedback Pin Bias Current
Set Pin Bias Current
V
OL
A
V
Gain Block Output Low
Reference Line Regulation
Gain Block Gain
Current Limit
Current Limit Temperature Coefficient
Switch OFF Leakage Current
V
SW2
Maximum Excursion Below GND
Measured at SW1 Pin, V
SW1
= 12V
I
SW1
≤
10µA, Switch OFF
CONDITIONS
LT1107, V
FB
= 0V
V
SET
= V
REF
I
SINK
= 300µA, V
SET
= 1V
5V
≤
V
IN
≤
30V
R
L
= 100k (Note 4)
220Ω to I
LIM
to V
IN
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
TYP
70
70
0.15
0.02
MAX
120
300
0.4
0.075
UNITS
nA
nA
V
%/V
V/V
mA
%/°C
1000
6000
400
– 0.3
1
– 400
10
– 350
µA
mV
The
q
denotes the specifications which apply over the full operating temperature range, V
IN
= 3V, – 55°C
≤
T
A
≤
125°C, unless
otherwise noted.
SYMBOL
I
Q
f
OSC
DC
t
ON
PARAMETER
Quiescent Current
Oscillator Frequency
Duty Cycle
Switch ON Time
Reference Line Regulation
V
SAT
Switch Saturation Voltage, Step-Up Mode
Switch Saturation Voltage, Step-Down Mode
Step-Up Mode
Step-Down Mode, V
IN
= 12V
Step-Up Mode
Step-Down Mode, V
IN
= 12V
2V
≤
V
IN
≤
5V, 0°C
≤
T
A
≤
125°C
2.4V
≤
V
IN
≤
5V, T
A
= – 55°C
0°C
≤
T
A
≤
125°C, I
SW
= 500mA
T
A
= – 55°C, I
SW
= 400mA
V
IN
= 12V, I
SW
= 500mA
0°C
≤
T
A
≤
125°C
T
A
= – 55°C
CONDITIONS
Switch OFF
q
q
q
q
q
q
MIN
40
56
45
7
5
LT1107M
TYP
MAX
500
63
69
60
11
9
0.2
0.5
0.5
95
81
73
15
13
0.4
0.8
0.65
0.65
1.5
2.0
UNITS
µA
kHz
%
%
µs
µs
%/V
%/V
V
V
V
V
The
q
denotes the specifications which apply over the full operating temperature range, V
IN
= 3V, 0°C
≤
T
A
≤
70°C, unless otherwise
noted.
SYMBOL
I
Q
f
OSC
DC
t
ON
PARAMETER
Quiescent Current
Oscillator Frequency
Duty Cycle
Switch ON Time
Reference Line Regulation
V
SAT
Switch Saturation Voltage, Step-Up Mode
Switch Saturation Voltage, Step-Down Mode
Step-Up Mode
Step-Down Mode, V
IN
= 12V
Step-Up Mode
Step-Down Mode, V
IN
= 12V
2V
≤
V
IN
≤
5V
V
IN
= 3V, I
SW
= 650mA
V
IN
= 12V, I
SW
= 650mA
CONDITIONS
Switch OFF
q
q
q
q
q
q
q
q
q
MIN
50
62
50
8
6
LT1107C
TYP
63
69
60
11
9
0.2
0.5
1.1
MAX
450
88
78
70
13.5
12.0
0.7
0.65
1.5
UNITS
µA
kHz
%
%
µs
µs
%/V
V
V
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
This specification guarantees that both the high and low trip points
of the comparator fall within the 1.2V to 1.3V range.
Note 3:
The output voltage waveform will exhibit a sawtooth shape due to
the comparator hysteresis. The output voltage on the fixed-output versions
will always be within the specified range.
Note 4:
100k resistor connected between a 5V source and the AO pin.
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LT1107
TYPICAL PERFOR A CE CHARACTERISTICS
Saturation Voltage, Step-Up Mode
(SW2 Pin Grounded)
1.2
1.0
1.4
1.3
SATURATION VOLTAGE (V)
SWITCH ON VOLTAGE (V)
V
IN
= 3V
0.8
V
IN
= 2V
0.6
0.4
0.2
0
V
IN
= 5V
1.2
1.1
1.0
0.9
0.8
0.7
0
SWITCH CURRENT (A)
0
0.2
0.4
0.6
0.8
SWITCH CURRENT (A)
Quiescent Current
400
350
400
380
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
300
250
200
150
100
–55 –35 –15
FREQUENCY (kHz)
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G05
Switch ON Time
Step-Up Mode
16
15
14
SWITCH ON TIME (µs)
DUTY CYCLE (%)
13
12
11
10
9
8
7
6
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G08
SWITCH ON TIME (µs)
4
U W
1.0
1107 G01
Switch ON Voltage, Step-Down
Mode (SW1 Pin Connected to V
IN
)
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Maximum Switch Current vs R
LIM
STEP-UP
2V
≤
V
IN
≤
5V
STEP-DOWN
V
IN
= 12V
1.2
0.1
0.2
0.6
SWITCH CURRENT (A)
0.3
0.4
0.5
0.7
0.8
10
100
R
LIM
(Ω)
1000
1107 G03
1107 G02
Quiescent Current
100
T
A
= 25°C
90
80
70
60
50
40
30
0
3
6
9 12 15 18 21 24 27 30
INPUT VOLTAGE (V)
1107 G06
Oscillator Frequency
360
340
320
300
280
260
240
220
200
20
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G07
Duty Cycle
Step-Up Mode
85
80
75
70
65
60
55
50
45
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G09
Switch ON Time
Step-Down Mode
13
12
11
10
9
8
7
6
5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G10
1107fa
LT1107
TYPICAL PERFOR A CE CHARACTERISTICS
Minimum/Maximum Frequency
vs ON Time, Step-Down Mode
100
90
FREQUENCY (kHz)
FREQUENCY (kHz)
DUTY CYCLE (%)
80
70
60
50
40
30
4
5
6
7
–55°C
≤
T
A
≤
125°C
0°C
≤
T
A
≤
70°C
8 9 10 11 12 13 14
ON TIME (µs)
1107 G11
LT1107-5
Output Voltage
5.3
5.2
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
12.10
12.05
12.00
11.95
11.90
11.85
TRIP POINT VOLTAGE (V)
5.1
5.0
4.9
4.8
4.7
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G16
PI FU CTI
S
GND (Pin 5):
Ground.
AO (Pin 6):
Auxiliary Gain Block (GB) Output. Open collector,
can sink 300µA.
SET (Pin 7):
GB Input. GB is an op amp with positive input
connected to SET pin and negative input connected to
1.25V reference.
FB/SENSE (Pin 8):
On the LT1107 (adjustable), this pin
goes to the comparator input. On the LT1107-5 and
LT1107-12, this pin goes to the internal application resistor
that sets output voltage.
I
LIM
(Pin 1):
Connect this pin to V
IN
for normal use. Where
lower current limit is desired, connect a resistor between
I
LIM
and V
IN
. A 220Ω resistor will limit the switch current
to approximately 400mA.
V
IN
(Pin 2):
Input Supply Voltage.
SW1 (Pin 3):
Collector of Power Transistor. For step-up
mode connect to inductor/diode. For step-down mode
connect to V
IN
.
SW2 (Pin 4):
Emitter of Power Transistor. For step-up
mode connect to ground. For step-down mode connect to
inductor/diode. This pin must never be allowed to go more
than a Schottky diode drop below ground.
U W
Minimum/Maximum Frequency
vs ON Time, Step-Up Mode
100
90
80
70
60
50
40
30
6
7
8
9
10 11 12 13 14 15 16
ON TIME (µs)
1107 G12
Duty Cycle
Step-Down Mode
70
65
60
55
50
45
40
35
–55 –35 –15
0°C
≤
T
A
≤
70°C
T
A
= 25°C
–55°C
≤
T
A
≤
125°C
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G13
LT1107-12
Output Voltage
12.20
12.15
1.30
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
LT1107
Feedback Voltage
11.80
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G17
1.20
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1107 G18
UO
U
U
1107fa
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