EL7564C
Monolithic 4 Amp DC:DC Step-down Regulator
However, due to the superimpose of VC and VIN, the
choice of RA and RB are restricted by the following
relationship:
2. Offset Tracking
The intended start-up sequence is shown in Figure 3a. In
this configuration, VC will not start until VP reaches a
preset value of:
R
R
A
B
-------------------
´ V
C
V
+ 0.5 < ------------------- ´ V
+
P
IN
R
+ R
B
R
+ R
B
A
A
R
B
------------------- ´ V
IN
R
+ R
B
A
Where 0.5 is for noise immunity. See Figure 3 below.
R
B
1
20
19
15
14
13
12
11
2
6
V
C
EL7564C
7
V
IN
V
P
R
A
8
STP
V
OUT
V
C
9
+
-
STN
10
TIME
1
2
20
19
15
14
13
12
11
6
V
P
7
EL7564C
8
STP
9
+
-
STN
10
Figure 3. Offset Power Tracking
12
ELANTEC [ ELANTEC SEMICONDUCTOR ]
