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LT1107IS8#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
4
LT1107
1107fa
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
Saturation Voltage, Step-Up Mode Switch ON Voltage, Step-Down
(SW2 Pin Grounded) Mode (SW1 Pin Connected to V
IN
) Maximum Switch Current vs R
LIM
Quiescent Current
Quiescent Current
TEMPERATURE (°C)
–55
FREQUENCY (kHz)
–15
25
45 125
1107 G07
–35 5
65
85
105
100
90
80
70
60
50
40
30
20
Oscillator Frequency
Switch ON Time
Step-Down Mode
TEMPERATURE (°C)
–55
SWITCH ON TIME (µs)
–15
25
45 125
1107 G10
–35 5
65
85
105
13
12
11
10
9
8
7
6
5
TEMPERATURE (°C)
–55
DUTY CYCLE (%)
–15
25
45 125
1107 G09
–35 5
65
85
105
85
80
75
70
65
60
55
50
45
Duty Cycle
Step-Up Mode
TEMPERATURE (°C)
–55
QUIESCENT CURRENT (µA)
–15
25
45 125
1107 G05
–35 5
65
85
105
400
350
300
250
200
150
100
TEMPERATURE (°C)
–55
SWITCH ON TIME (µs)
–15
25
45 125
1107 G08
–35 5
65
85
105
16
15
14
13
12
11
10
9
8
7
6
Switch ON Time
Step-Up Mode
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (µA)
400
380
360
340
320
300
280
260
240
220
200
24
1107 G06
6
12
18
30
3
9152127
T
A
= 25°C
R
LIM
(Ω)
SWITCH CURRENT (A)
10
1107 G03
100
1.5
1.4
1.3
1.2
1.1
0.9
0.8
1000
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1.0
STEP-DOWN
V
IN
= 12V
STEP-UP
2V ≤ V
IN
≤ 5V
SWITCH CURRENT (A)
0
SWITCH ON VOLTAGE (V)
0.6
1107 G02
0.2 0.4 0.8
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.1 0.3 0.5 0.7
SWITCH CURRENT (A)
0
SATURATION VOLTAGE (V)
1.2
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4 0.6 0.8
1107 G01
1.0 1.2
V
IN
= 3V
V
IN
= 2V V
IN
= 5V
5
LT1107
1107fa
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.
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.
PI
U
FU
U
C
U
S
O
TI
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
Minimum/Maximum Frequency Minimum/Maximum Frequency
vs ON Time, Step-Down Mode vs ON Time, Step-Up Mode
TEMPERATURE (°C)
–55
DUTY CYCLE (%)
–15
25
45 125
1107 G13
–35 5
65
85
105
70
65
60
55
50
45
40
35
TEMPERATURE (°C)
–55
OUTPUT VOLTAGE (V)
–15
25
45 125
1107 G16
–35 5
65
85
105
5.3
5.2
5.1
5.0
4.9
4.8
4.7
TEMPERATURE (°C)
–55
OUTPUT VOLTAGE (V)
–15
25
45 125
1107 G17
–35 5
65
85
105
12.20
12.15
12.10
12.05
12.00
11.95
11.90
11.85
11.80
LT1107-5 LT1107-12 LT1107
Output Voltage Output Voltage Feedback Voltage
TEMPERATURE (°C)
–55
TRIP POINT VOLTAGE (V)
–15
25
45 125
1107 G18
–35 5
65
85
105
1.30
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.20
ON TIME (µs)
4
FREQUENCY (kHz)
100
90
80
70
60
50
40
30
5
9
11
1107 G11
8
13
14
6
7
10 12
0°C ≤ T
A
≤ 70°C
–55°C ≤ T
A
≤ 125°C
ON TIME (µs)
6
FREQUENCY (kHz)
100
90
80
70
60
50
40
30
7
11
13
1107 G12
10
15
16
8
9
12 14
0°C ≤ T
A
≤ 70°C
–55°C ≤ T
A
≤ 125°C
T
A
= 25°C
Duty Cycle
Step-Down Mode
6
LT1107
1107fa
W
IDAGRA
B
L
O
C
K
S
OPERATIO
U
The LT1107 is a gated oscillator switcher. This type
architecture has very low supply current because the
switch is cycled when the feedback pin voltage drops
below the reference voltage. Circuit operation can best be
understood by referring to the LT1107 block diagram.
Comparator A1 compares the feedback (FB) pin voltage
with the 1.25V reference signal. When FB drops below
1.25V, A1 switches on the 63kHz oscillator. The driver
amplifier boosts the signal level to drive the output NPN
power switch. The switch cycling action raises the output
voltage and FB pin voltage. When the FB voltage is suffi-
cient to trip A1, the oscillator is gated off. A small amount
of hysteresis built into A1 ensures loop stability without
external frequency compensation. When the comparator
output is low, the oscillator and all high current circuitry is
turned off, lowering device quiescent current to just 300µA.
The oscillator is set internally for 11µs ON time and 5µs
OFF time in step-up mode, optimizing the device for
converters where V
OUT
≈ 3V
IN
. The combination of high
duty cycle and the current limit feature enables continuous
mode operation in many applications, increasing available
output power.
OSCILLATOR
1.25V
REFERENCE
V
IN
GND
SENSE
COMPARATOR
A2
A1
DRIVER
I
LIM
SW1
SW2
AO
GAIN BLOCK/
ERROR AMP
SET
1107 BD02
R1
R2
220k LT1107-5: R1 = 73.5k
LT1107-12: R1 = 25.5k
OSCILLATOR
1.25V
REFERENCE
V
IN
GND FB
COMPARATOR
A2
A1
DRIVER
I
LIM
SW1
SW2
AO
GAIN BLOCK/
ERROR AMP
SET
1107 BD01
LT1107
LT1107-5/LT1107-12
Gain block A2 can serve as a low-battery detector. The
negative input of A2 is the 1.25V reference. A resistor
divider from V
IN
to GND, with the mid-point connected to
the SET pin provides the trip voltage in a low-battery
detector application. AO can sink 300µA (use a 22k
resistor pull-up to 5V).
A resistor connected between the I
LIM
pin and V
IN
sets
maximum switch current. When the switch current ex-
ceeds the set value, the switch cycle is prematurely
terminated. If current limit is not used, I
LIM
should be tied
directly to V
IN
. Propagation delay through the current limit
circuitry is approximately 1µs.
In step-up mode the switch emitter (SW2) is connected to
ground and the switch collector (SW1) drives the induc-
tor; in step-down mode the collector is connected to V
IN
and the emitter drives the inductor.
The LT1107-5 and LT1107-12 are functionally identical to
the LT1107. The -5 and -12 versions have on-chip voltage
setting resistors for fixed 5V or 12V outputs. Pin 8 on the
fixed versions should be connected to the output. No
external resistors are needed.
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LT1107IS8#PBF

Mfr. #:
Buy LT1107IS8#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Micropower DC/DC Converter Adjustable and Fixed 5V, 12V
Lifecycle:
New from this manufacturer.
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