
TL497A
500mA PEAK STEPUP, STEPDOWN, INVERTING SWITCHING VOLTAGE REGULATOR
SLVS009F JUNE 1976 REVISED FEBRUARY 2005
5
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
APPLICATION INFORMATION
VI
L
14
13
10
8
7
6
5
4
3
2
1
TL497A
R2 = 1.2 k
R1
VO
CO
BASIC CONFIGURATION
(Peak Switching Current = I(PK) < 500 mA)
VI
RCL
L
R1
8
10
13
14
12
3
4
5
EXTENDED POWER CONFIGURATION
(using external transistor)
TL497A
DESIGN EQUATIONS
I
(PK) +
2I
O
max
V
O
V
I
L(
mH) +
V
I
(PK)
ton (ms)
C
T
(pF)
[ 12 ton (ms)
R1
+ (V
O
–1.2 V) k
W
Choose L (50 to 500
H), calculate
ton (25 to 150 s)
R
CL +
0.5 V
I
(PK)
C
O
(
mF) [ ton(ms)
V
I
V
O
I
(PK) )
I
O
V
ripple
(PK)
CT
R2 = 1.2 k
VO
CO
CT
RCL
Figure 1. Positive Regulator, Step-Up Configurations