LTC1174-3.3 Linear Technology, LTC1174-3.3 Datasheet - Page 5

• Manufacturer Part Number: LTC1174-3.3
• Description: High Efficiency Step-Down and Inverting DC/DC Converter
• Manufacturer: Linear Technology

PI FU CTIO S
TYPICAL PERFOR
V
main voltage comparator’s input. On the LTC1174-3.3 and
LTC1174-5 this pin goes to an internal resistive divider
which sets the output voltage.
LB
pin will sink current when pin 3 (LB
During shutdown this pin goes to high impedance.
LB
Comparator. The “+” input is connected to a reference
voltage of 1.25V.
GND (Pin 4): Ground Pin.
OUT
2.0
1.5
1.0
0.5
OUT
IN
95
94
93
92
91
90
89
U
0
0
Efficiency vs Input Voltage
5
Operating Frequency
vs V
(V
(Pin 3): The “–” Input of the Low-Battery Voltage
(Pin 2): Open Drain of an N-Channel Pull-Down. This
V
FB
OUT
6
1
IN
I
LOAD
) (Pin 1): For the LTC1174, this pin connects to the
= 5V
I
U
– V
PGM
7
2
(V
= 300mA
IN
OUT
INPUT VOLTAGE (V)
= V
8
3
– V
IN
T
OUT
A
9
4
= 25°C
) VOLTAGE (V)
T
U
10
5
A
V
L = 100 H
COIL = CTX100-4
= 70°C
OUT
I
I
LOAD
PGM
11
6
= 5V
= 0V
= 100mA
12
W
7
13
1174 G10
A
8
1174 G13
U
14
9
IN
CE
) goes below 1.25V.
C
HARA TERISTICS
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0
0
Supply Current in Shutdown
Switch Resistance vs
Input Voltage
4
SHUTDOWN = 0V
T
CURRENT INTO PIN 6 ONLY
A
= 25°C
2
6
LTC1174
C
8
4
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LTC1174HV
10
6
12
SW (Pin 5): Drain of the P-Channel MOSFET Switch. Cathode
of Schottky diode must be closely connected to this pin.
V
close to ground pin 4.
I
Switch. With I
with I
SHUTDOWN (Pin 8): Pulling this pin to ground keeps the
internal switch off and puts the LTC1174 in micropower
shutdown.
PGM
IN
8
14
(Pin 6): Input Supply Voltage. It must be decoupled
PGM
(Pin 7): Selects the Current Limit of the P-Channel
10
16
T
A
= 25°C
12
= 0V, the current trip value is reduced to 340mA.
1174 G11
18
1174 G14
PGM
14
20
LTC1174-3.3/LTC1174-5
= V
IN
, the current trip point is 600mA and
500
450
400
350
300
250
200
150
100
50
50
40
30
20
10
0
0
0
0
Off-Time vs Output Voltage
DC Supply Current
LTC1174HV-3.3
T
A
LTC1174-3.3
= 25°C
2
ACTIVE MODE
1
4
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
SLEEP MODE
LTC1174-5
LTC1174HV-5
2
6
8
LTC1174
3
I
I
PGM
PGM
10
= V
= 0V
IN
4
12
1174 G12
1174 G15
5
14
5