LT1108 Datasheet, PDF (3/12 Pages) Linear Technology – Micropower DC/DC Converter Adjustable and Fixed 5V, 12V

LT1108
ELECTRICAL CHARACTERISTICS TA = 25°C, VIN = 3V, unless otherwise noted.
SYMBOL PARAMETER
V_SAT
SW_SAT Voltage, Step-Down Mode
A_V
Gain Block Gain
Current Limit
Current Limit Temperature Coefficient
Switch OFF Leakage Current
V_SW2
Maximum Excursion Below GND
CONDITIONS
V_IN = 12V, I_SW = 650mA
R_L = 100k (Note 3)
220Ω from I_LIM to V_IN
Measured at SW1 Pin
I_SW1 ≤ 10µA, Switch OFF
MIN TYP MAX
1.1
1.5
q
1.7
q 400 1000
400
q
– 0.3
1
10
– 400 – 350
UNITS
V
V
V/ V
mA
%/°C
µA
mV
The q 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.
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.
TYPICAL PERFOR A CE CHARACTERISTICS
Saturation Voltage Step-Up Mode
(SW2 Pin Grounded)
1.2
1.0
V_IN = 3V
0.8
V_IN = 2V
0.6
V_IN = 5V
0.4
0.2
0
0 0.2 0.4 0.6 0.8 1.0 1.2
SWITCH CURRENT (A)
LT1108 • TPC01
Saturation Voltage Step-Up Mode
(SW2 Pin Grounded)
1000
900
V_OUT = 5V
800
700
V_IN = 24V
L = 500µH
600
500
400
V_IN = 12V
L = 250µH
300
200
100
0
100
R _LIM (Ω)
1000
LT1108 • TPC04
Switch ON Voltage
Step-Down Mode
(SW1 Pin Connected to V_IN)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
SWITCH CURRENT (A)
LT1108 • TPC02
Maximum Switch Current
vs R_LIM
1200
1100
2V ≤ V_IN ≤ 5V
1000
900
800
700
600
500
400
300
200
100
10
100
R_LIM (Ω)
1000
LT1108 • TPC03
Supply Current vs Switch Current
50
40
30
V_IN = 5V
20
10
V_IN = 2V
0
0
200 400 600 800 1000
SWITCH CURRENT (mA)
LTC1108 • TPC05
Quiescent Current
120
115
110
105
100
95
90
85
80
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
LT1108 • TPC06
3