Datasheet
2
LT1109A
A
U
G
W
A
W
U
W
ARB
S
O
LU
T
EXI T
I
S
(Voltages Referred to GND Pin)
Supply Voltage (V
IN
) ................................ – 0.4V to 20V
SW Pin Voltage........................................ – 0.4V to 50V
Feedback Pin Voltage (LT1109A)........................... 5.5V
Shutdown Pin Voltage ........................................... 5.5V
Switch Current.......................................................... 2A
Maximum Power Dissipation ............................ 300mW
Operating Temperature Range .................... 0°C to 70°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
T
JMAX
= 90°C, θ
JA
= 150°C/W
1
2
3
4
8
7
6
5
TOP VIEW
S8 PACKAGE
8-LEAD PLASTIC SO
*FIXED VERSIONS
V
IN
NC
SW
PGND
FB (SENSE)*
SHUTDOWN
NC
GND
LT1109ACS8
LT1109ACS8-5
LT1109ACS8-12
1109A
1109A5
1109A1
LT1109ACN8
LT1109ACN8-5
LT1109ACN8-12
WU
U
PACKAGE
/
O
RDER I FOR ATIO
ORDER PART
NUMBER
1
2
3
4
8
7
6
5
TOP VIEW
V
IN
NC
SW
PGND
N8 PACKAGE
8-LEAD PLASTIC DIP
*FIXED VERSIONS
FB (SENSE)*
SHUTDOWN
NC
GND
ORDER PART
NUMBER
S8 PART
MARKING
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 ● 360 500 µA
V
IN
Input Voltage ● 29V
Comparator Trip Point Voltage LT1109A ● 1.20 1.25 1.30 V
V
OUT
Output Sense Voltage LT1109A-5; 2V ≤ V
IN
≤ 5V ● 4.75 5.00 5.25 V
LT1109A-12; 2V ≤ V
IN
≤ 12V ● 11.52 12.00 12.55 V
Comparator Hysteresis LT1109A ● 8 12.5 mV
Output Voltage Ripple LT1109A-5
● 25 50 mV
LT1109A-12 ● 60 120 mV
f
OSC
Oscillator Frequency 105 120 135 kHz
● 95 155 kHz
t
ON
Switch On Time 4.1 5.5 6.9 µs
● 3.8 7.4 µs
DC Duty Cycle Full Load ● 60 68 77 %
V
CESAT
Switch Saturation Voltage V
IN
= 3V, I
SW
= 650mA ● 0.5 0.65 V
V
IN
= 5V, I
SW
= 1A 0.7 1.00 V
Switch Leakage Current V
SW
= 12V 1 10 µA
V
IH
SHUTDOWN Pin High ● 2.0 V
V
IL
SHUTDOWN Pin Low ● 0.8 V
I
IH
SHUTDOWN Pin Input Current V
SHUTDOWN
≥ 2.0V ● 10 µA
I
L
SHUTDOWN Pin Input Current 0V ≤ V
SHUTDOWN
≤ 0.8V ● 20 µA
The ● denotes specifications which apply over the full operating
temperature range.
T
JMAX
= 90°C, θ
JA
= 130°C/W