Datasheet

3
LT1108
T
A
= 25°C, V
IN
= 3V, unless otherwise noted.
E
LECTR
IC
AL C CHARA TERIST
ICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
SAT
SW
SAT
Voltage, Step-Down Mode V
IN
= 12V, I
SW
= 650mA 1.1 1.5 V
● 1.7 V
A
V
Gain Block Gain R
L
= 100k (Note 3) ● 400 1000 V/V
Current Limit 220Ω from I
LIM
to V
IN
400 mA
Current Limit Temperature Coefficient ● –0.3 %/°C
Switch OFF Leakage Current Measured at SW1 Pin 1 10 µA
V
SW2
Maximum Excursion Below GND I
SW1
≤ 10µA, Switch OFF –400 –350 mV
Note 2: 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 3: 100k resistor connected between a 5V source and the A0 pin.
The
● denotes specifications which apply over the full operating
temperature range.
Note 1: This specification guarantees that both the high and low trip points
of the comparator fall within the 1.2V to 1.3V range.
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
R
LIM
(Ω)
10
SWITCH CURRENT (mA)
100 1000
LT1108 • TPC03
1000
1200
1100
900
800
700
600
500
400
300
200
100
2V ≤ V
IN
≤ 5V
Saturation Voltage Step-Up Mode
(SW2 Pin Grounded)
Switch ON Voltage
Step-Down Mode
(SW1 Pin Connected to V
IN
)
Maximum Switch Current
vs R
LIM
Saturation Voltage Step-Up Mode
(SW2 Pin Grounded)
R
LIM
(Ω)
100
0
SWITCH CURRENT (mA)
200
400
600
800
1000
LT1108 • TPC04
100
300
500
700
900
1000
V
OUT
= 5V
V
IN
= 24V
L = 500µH
V
IN
= 12V
L = 250µH
Supply Current vs Switch Current Quiescent Current
TEMPERATURE (°C)
–50
QUIESCENT CURRENT (µA)
95
100
105
25
75
LT1108 • TPC06
90
85
80
–25 0 50
110
115
120
100
SWITCH CURRENT (A)
0
0
V
CESAT
(V)
0.2
0.4
0.6
0.8
1.2
0.2
0.4 0.6 0.8
LT1108 • TPC01
1.0 1.2
1.0
V
IN
= 2V
V
IN
= 5V
V
IN
= 3V
SWITCH CURRENT (A)
0
SWITCH ON VOLTAGE (V)
1.1
1.2
1.3
0.6
LT1108 • TPC02
1.0
0.9
0.2 0.4 0.8
0.8
0.7
1.4
0.5
0.1 0.3 0.7
SWITCH CURRENT (mA)
0
SUPPLY CURRENT (mA)
30
40
50
800
LTC1108 • TPC05

20
10
0
200
400
600
1000
V
IN
= 5V
V
IN
= 2V