L4978
Table 6. Electrical Characteristcs
(T
j
= 25°C, C
osc
= 2.7nF, R
osc
= 20kΩ, V
CC
= 24V, unless otherwise specified). “
●
"
Specification Referred
to T
j
from 0 to 125°C
Symbol
Parameter
Ramp Valley
Ramp peak
Maximum duty cycle
Maximum Frequency
Duty Cycle = 0%
R
osc
= 13kΩ, C
osc
= 820pF
V
cc
= 8V
V
cc
= 55V
Test Condition
Min.
0.78
2
9
95
Typ.
0.85
2.15
9.6
97
300
Max.
0.92
2.3
10.2
Unit
V
V
V
%
kHz
OSCILLATOR SECTION
Figure 4. Test and evaluation board circuit.
Vi=8V to 55V
5
R
1
20K
3
C
1
220µF
63V
C
7
220nF
C
2
2.7nF
2
7
8
L4978
4
1
6
L1
126µH
(77120)
C
8
330µF
V
O
=3.3V/2A
R
3
C
5
100nF
R
2
9.1K
C
4
22nF
C
6
100nF
D1
STPS3L60U
R
4
D98IN834B
C1=220µF/63V EKE
C2=2.7nF
C5=100nF
C6=100nF
C7=220nF/63V
C8=330µF/35V CG Sanyo
L1=126µH KoolMu 77120 - 55 Turns - 0.5mm
R1=20K
R2=9.1K
D1=STPS3L60U
L4978
V
O
(V)
3.3
5.1
12
15
18
24
R3(KΩ)
0
2.7
12
16
20
30
4.7
4.7
4.7
4.7
4.7
R4(KΩ)
Figure 5. PCB and component layout of the figure 4.
5/13
STMICROELECTRONICS [ STMICROELECTRONICS ]
