Datasheet

2
LT1108
A
U
G
W
A
W
U
W
ARB
S
O
LU
T
EXI T
I
S
Supply Voltage (V
IN
)............................................... 36V
SW1 Pin Voltage (V
SW1
) ......................................... 50V
SW2 Pin Voltage (V
SW2
) ............................ –0.5V to V
IN
Feedback Pin Voltage (LT1108) ............................. 5.5V
Sense Pin Voltage (LT1108, -5, -12) ...................... 36V
Maximum Power Dissipation ............................ 500mW
Maximum Switch Current ...................................... 1.5A
Operating Temperature Range .................... 0°C to 70°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
WU
U
PACKAGE
/
O
RDER I FOR ATIO
ORDER PART
NUMBER
LT1108CS8
LT1108CS8-5
LT1108CS8-12
S8 PART MARKING
ORDER PART
NUMBER
LT1108CN8
LT1108CN8-5
LT1108CN8-12
T
JMAX
= 90°C, θ
JA
= 150°C/W
T
JMAX
= 90°C, θ
JA
= 130°C/W
1
2
3
4
8
7
6
5

TOP VIEW
I
LIM

V
IN

SW1
SW2
FB (SENSE*)
SET
A0
GND
N8 PACKAGE
8-LEAD PLASTIC DIP
*FIXED VERSIONS
1
2
3
4
8
7
6
5

TOP VIEW
I
LIM

V
IN

SW1
SW2
FB (SENSE*)
SET
A0
GND
S8 PACKAGE
8-LEAD PLASTIC SOIC
*FIXED VERSIONS
E
LECTR
IC
AL C CHARA TERIST
ICS
T
A
= 25°C, V
IN
= 3V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
Q
Quiescent Current Switch OFF ● 110 150 µA
Quiescent Current, Boost Mode Configuration No Load LT1108-5 135 µA
LT1108-12 250 µA
V
IN
Input Voltage Step-Up Mode ● 2 12.6 V
Step-Down Mode ● 30.0 V
Comparator Trip Point Voltage LT1108 (Note 1) ● 1.2 1.245 1.3 V
V
OUT
Output Sense Voltage LT1108-5 (Note 2) ● 4.75 5 5.25 V
LT1108-12 (Note 2) ● 11.4 12 12.6 V
Comparator Hysteresis LT1108 ● 510 mV
Output Hysteresis LT1108-5 ● 20 40 mV
LT1108-12
● 50 100 mV
f
OSC
Oscillator Frequency ● 14 19 25 kHz
Duty Cycle Full Load, Step-Up Mode ● 63 70 78 %
t
ON
Switch-ON Time I
LIM
Tied to V
IN
, Step-Up Mode ● 28 36 48 µs
Feedback Pin Bias Current LT1108, V
FB
= 0V ● 10 50 nA
Set Pin Bias Current V
SET
= V
REF
● 20 100 nA
V
OL
Gain Block Output Low I
SINK
= 100µA, V
SET
= 1V ● 0.15 0.4 V
Reference Line Regulation 2V ≤ V
IN
≤ 5V ● 0.20 0.400 %/V
5V ≤ V
IN
≤ 30V ● 0.02 0.075 %/V
V
SAT
SW
SAT
Voltage, Step-Up Mode V
IN
= 3V, I
SW
= 650mA ● 0.5 0.65 V
V
IN
= 5V, I
SW
= 1A 0.8 1.00 V
1108
10805
10812