10
LT1304/LT1304-3.3/LT1304-5
OPERATIO
U
LOAD CURRENT (mA)
1
ELECTROCHEMICAL EFFICIENCY (%)
100
90
80
70
60
50
40
30
20
10
0
10 100
1304 F12
200
TYPICAL APPLICATIONS
U
V
IN
SW
SHDN GND
LBILBO
I
LIM
FB
LT1304
+
+
220µF
100µF
0.01µF
47k
2 CELLS
33µH**
I
Q
≈ 10µA
5V
100mA
1% METAL FILM
SUMIDA CD54-330
*
**
1304 TA03
47k 22k
1.21M*
3.83M*
MBR0530
200k
2N3906
Super Burst
TM
Low I
Q
DC/DC Converter
LOAD CURRENT (mA)
40
50
70
60
80
90
EFFICIENCY (%)
100
1304 TA04
0.01 0.1 1.0 10
V
IN
= 3V
V
IN
= 2V
Super Burst
Efficiency
Super Burst is a trademark of Linear Technology Corporation.
Figure 12 shows overall energy conversion efficiency,
assuming availability of 6.5WH of battery energy. This
efficiency approximates the electrical efficiency at load
current levels from 1mA to 10mA, but drops severely at
load currents above 10mA (load power above 50mW). The
moral of the story is this: if your system needs 5V at more
than 40mA to 50mA, consider using a NiCd battery (1/10
the internal impedance) instead of a AA cell alkaline
battery.
Figure 12. Overall System Efficiency Including Battery Efficiency
vs Load Current. Internal Impedance of Alkaline AA Cells
Accounts for Rapid Drop in Efficiency at Higher Load Current
