Datasheet
LT3971/LT3971-3.3/LT3971-5
24
3971fd
TYPICAL APPLICATIONS
4V Step-Down Converter with a High Impedance Input Source
10pF
SW
FB
SS
RT
V
IN
24V
V
OUT
4V
1.2A*
4.7µF
C
BULK
100µF
0.47µF
100µF
412k
49.9k
f = 800kHz
4.7µH
1M
GND
BD
SYNC
11M
LT3971
3971 TA09a
EN BOOST
PG
1nF
1M
+
–
+
* AVERAGE OUTPUT POWER CANNOT
EXCEED THAT WHICH CAN BE PROVIDED
BY HIGH IMPEDANCE SOURCE.
NAMELY,
WHERE V IS VOLTAGE OF SOURCE, R IS
INTERNAL SOURCE IMPEDANCE, AND η IS
LT3971 EFFICIENCY. MAXIMUM OUTPUT
CURRENT OF 1.2A CAN BE SUPPLIED FOR A
SHORT TIME BASED ON THE ENERGY
WHICH CAN BE SOURCED BY THE BULK
INPUT CAPACITANCE.
P
POUT(MAX) = • η
OUT(MAX)
POUT(MAX) = • η
POUT(MAX) = • η
POUT(MAX) = • η
POUT(MAX) = • η
POUT(MAX) = • η
POUT(MAX) = • η
POUT(MAX) = • η
POUT(MAX) = • η
= •
POUT(MAX) = • η
POUT(MAX) = • η
η
POUT(MAX) = • η
V
POUT(MAX) = • η
2
POUT(MAX) = • η
4R
POUT(MAX) = • η
POUT(MAX) = • η
500µs/DIV
3971 TA09b
V
IN
5V/DIV
V
OUT
200mV/DIV
I
L
1A/DIV
Sourcing a Maximum Load Pulse Start-Up from High Impedance Input Source
2ms/DIV
3971 TA09c
V
IN
1V/DIV
V
OUT
2V/DIV
I
L
500mA/DIV
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
3.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
0.40 ± 0.10
BOTTOM VIEW—EXPOSED PAD
1.65 ± 0.10
(2 SIDES)
0.75 ±0.05
R = 0.125
TYP
2.38 ±0.10
(2 SIDES)
15
106
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DD) DFN REV C 0310
0.25 ± 0.05
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 ±0.05
(2 SIDES)2.15 ±0.05
0.50
BSC
0.70 ±0.05
3.55 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER