L296 - L296P
Figure 35 : P.C. Board and ComponentLayoutof the Circuit of fig. 34 (1:1 scale)
SELECTION OF COMPONENT VALUES (see fig. 34)
Allowed Rage
Recommended
Value
Component
Purpose
Notes
Min.
Max.
R1
R2
–
Set Input Voltage
Threshold for Reset.
–
Vi min
5
R1/R2
1
−
100 k
220k
Ω
Ω
If output voltage is sensed R1 and
R2 may be limited and pin 12
connected to pin 10.
R3
R4
4.3 kΩ
10 kΩ
Sets Switching Frequency 1 kΩ 100kΩ
Pull-down Resistor
22kΩ May be omitted and pin 6 grounded
if inhibit not used.
R5
R6
15 k
Frequency Compensation 10k
Ω
Ω
Collector Load For Reset
Output
VO
Omitted if reset function not used.
0.05A
R7
R8
–
Divider to Set Output
Voltage
–
–
–
1kΩ
VO − VREF
R7/R8 =
-
4.7 kΩ
VREF
Riim
–
Sets Current Limit Level
7.5kΩ
If Riim is omitted and pin 4 left open
the current limit is internally fixed.
C1
C2
C3
C4
10
F
Stability
2.2 F
µ
µ
2.2
F
Sets Reset Delay
Sets Switching Frequency
Soft Start
–
–
3.3nF
–
Omitted if reset function not used.
µ
2.2 nF
1 nF
1 µF
2.2 µF
Also determines average short
circuit current.
C5
C6
33 nF
Frequency Compensation
390 pF
High Frequency
Compensation
–
–
–
–
Not required for 5 V operation.
C7, C8
L1
100
300
F
Output Filter
µ
H
100 H
µ
µ
Q1
Crowbar Protection
The SCR must be able to withstand
the peak discharge current of the
output capacitor and the short
circuit current of the device.
D1
Recirculation Diode
7A Schottky or 35 ns trr Diode.
15/22
STMICROELECTRONICS [ ST ]
