LT1173 データシートの表示（PDF） - Linear Technology
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LT1173 Datasheet PDF : 16 Pages
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LT1173
TYPICAL PERFOR A CE CHARACTERISTICS
Quiescent Current vs Temperature
120
Supply Current vs Switch Current
50
VIN = 3V
40
110
30
VIN = 5V
100
90
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LT1173 •TPC06
20
VIN = 2V
10
0
0
200 400 600 800 1000
SWITCH CURRENT (mA)
LT1173 •TPC07
Oscillator Frequency
26.0
25.5
25.0
24.5
24.0
23.5
23.0
22.5
22.0
0
5 10 15 20 25 30
VIN(V)
LT1173 • TPC08
PI FU CTI S
ILIM (Pin 1): Connect this pin to VIN for normal use. Where
lower current limit is desired, connect a resistor between
ILIM and VIN. A 220Ω resistor will limit the switch current
to approximately 400mA.
VIN (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 VIN.
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
1.245V reference.
FB/SENSE (Pin 8): On the LT1173 (adjustable) this pin
goes to the comparator input. On the LT1173-5 and
LT1173-12, this pin goes to the internal application resis-
tor that sets output voltage.
BLOCK DIAGRA S
LT1173
SET
V IN
1.245V
REFERENCE
GND
FB
4
A2
AO
GAIN BLOCK/
ERROR AMP
I LIM
SW1
A1
OSCILLATOR
COMPARATOR
DRIVER
SW2
LT1173 • BD01
SET
V IN
1.245V
REFERENCE
R1
GND
LT1173-5, -12
A2
AO
GAIN BLOCK/
ERROR AMP
I LIM
SW1
A1
OSCILLATOR
R2
753k Ω
COMPARATOR
SENSE
DRIVER
SW2
LT1173-5: R1 = 250kΩ
LT1173-12: R1 = 87.4kΩ
LT1173 • BD02
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