LT1949 LINER [Linear Technology], LT1949 Datasheet - Page 4

• Manufacturer Part Number: LT1949
• Description: 600kHz, 1A Switch PWM DC/DC Converter
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
V
nect a series RC network from this pin to ground. Typical
values for compensation are a 68k/330pF combination
when using ceramic output capacitors. Minimize trace
area at V
FB (Pin 2): Feedback Pin. Reference voltage is 1.24V.
Connect resistor divider tap here. Minimize trace area at
FB. Set V
SHDN (Pin 3): Shutdown. Pull this pin low for shutdown
mode (only the low-battery detector remains active).
Leave this pin floating or tie to a voltage between 1.4V and
6V to enable the device. SHDN pin is logic level and need
only meet the logic specification (1.4V for high, 0.4V for
low).
LT1949
TYPICAL PERFOR A CE CHARACTERISTICS
50mV/DIV
4
COUPLED
C
OFFSET
ADDED
U
(Pin 1): Compensation Pin for Error Amplifier. Con-
V
26
25
24
23
22
21
20
OUT
DC
–50
Quiescent Current, SHDN = 0V
Load Regulation
V
V
L1 = 10 H, SUMIDA CD54
C
IN
OUT
OUT
C
OUT
= 3V
–25
U
.
= 10V
= 10 F CERAMIC
according to: V
TEMPERATURE ( C)
0
I
LOAD
U
25
25mA/DIV
50
W
OUT
75
1317 TPC10
1949 G10
= 1.24V(1 + R1/R2).
U
100
50mV/DIV
COUPLED
OFFSET
ADDED
V
OUT
DC
40
36
32
28
24
20
16
12
8
4
0
–50
Load Regulation
V
V
L1 = 10 H, SUMIDA CD54
C
FB Pin Bias Current
IN
OUT
OUT
= 4V
= 10V
= 10 F CERAMIC
–25
TEMPERATURE ( C)
I
0
LOAD
50mA/DIV
25
GND (Pin 4): Ground. Connect directly to local ground
plane.
SW (Pin 5): Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.
V
pin.
LBI (Pin 7): Low-Battery Detector Input. 200mV refer-
ence. Voltage on LBI must stay between ground and
700mV. Low-battery detector remains active in shutdown
mode.
LBO (Pin 8): Low-Battery Detector Output. Open collec-
tor, can sink 10 A. A 1M pull-up is recommended.
IN
(Pin 6): Supply Pin. Must be bypassed close to the
50
75
1317 TPC11
1949 G11
100
AC COUPLED
I
LOAD
500mA/DIV
100mV/DIV
200mA
100mA
V
–1
–2
–3
OUT
2
1
0
I
L
0
SHDN Pin Current
Transient Response
V
V
CIRCUIT OF FIGURE 1
IN
OUT
= 3.3V
1
= 10V
SHDN PIN VOLTAGE (V)
2
50 s/DIV
3
4
5
1317 TPC12
1949 G12
6