LT1073_1 Datasheet, PDF (4/16 Pages) Linear Technology – Micropower DC/DC Converter Adjustable and Fixed 5V, 12V

LT1073
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Temperature
150
V_IN = 1.5V
140
130
120
110
100
90
80
70
60
50
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
1073 G07
Recommended Minimum
Inductance Value
300
R_LIM = 0V
250
200
150
100
50
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
1073 G08
Guaranteed Minimum Output
Current at 5V vs V_IN
1000
100
FOR V_IN > 1.6V A
68Ω RESISTOR
MUST BE CONNECTED
BETWEEN I_LIM AND V_IN
10
1.0
1.5
2.0
2.5
3.0
3.5
V_IN (V)
1073 G09
PI FU CTIO S
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 collec-
tor, can sink 100µA.
SET (Pin 7): GB Input. GB is an op amp with positive input
connected to SET pin and negative input connected to
212mV reference.
FB/SENSE (Pin 8): On the LT1073 (adjustable) this pin
goes to the comparator input. On the LT1073-5 and
LT1073-12, this pin goes to the internal application resis-
tor that sets output voltage.
BLOCK DIAGRA S
SET
V_IN
LT1073
+
A2
A0
–
GAIN BLOCK/ERROR AMP
212mV
REFERENCE
GND
FB
A1
OSCILLATOR
COMPARATOR
I_LIM
SW1
Q1
DRIVER
SW2
1073 BD01
4
LT1073-5 and LT1073-12
SET
V_IN
212mV
REFERENCE
R1
GND
+
A2
A0
–
GAIN BLOCK/ERROR AMP
I_LIM
SW1
A1
OSCILLATOR
Q1
COMPARATOR
R2
940k
SENSE
DRIVER
SW2
LT1073-5: R1 = 40k
LT1073-12: R2 = 16.3k
1073 BD02