L7986TA STMicroelectronics, L7986TA Datasheet - Page 22

• Manufacturer Part Number: L7986TA
• Description: 3A step-down switching regulator
• Manufacturer: STMicroelectronics

Specifications of L7986TA

• Low Dropout Operation: 100% duty cycle

Application informations
22/43
Equation 24
where K is the feed forward constant and 1/K is equals to 18.
3.
Equation 25
4.
Equation 26
5.
Equation 27
The suggested maximum system bandwidth is equals to the switching frequency divided by
3.5 (F
For example with V
III compensation network is:
In
58 kHz and the phase margin is 50°.
R
Figure 11
1
=
Calculate C
Calculate C
Set also the first pole at four times the system bandwidth and also the second zero at
the output filter double pole:
SW
4.99kΩ
/3.5), anyway lower than 100 kHz if the F
is shown the module and phase of the open loop gain. The bandwidth is about
,
R
4
5
2
by placing the zero at 50% of the output filter double pole frequency (f
by placing the second pole at four times the system bandwidth (BW):
OUT
=
680Ω
=5 V, V
R
,
3
R
=
Doc ID 022098 Rev 1
3
IN
-------------------------- -
4 BW
----------------- 1
=
=24 V, I
⋅
f
C
LC
200Ω
5
R
1
=
–
R
------------------------------------------------------------- -
2π R
C
,
4
O
4
,
R
⋅
=3 A, L=18 μH, C
=
=
4
BW
--------- - K R
4
f
-------------------------- -
π R
=
LC
⋅
⋅
2kΩ
C
C
C
⋅
4
1
4
4
⋅
3
⋅
,
4 BW
SW
⋅
=
f
LC
⋅
---------------------------------------- -
2π R
C
1
is set higher than 500 kHz.
3
⋅
=
–
3.3nF
3
1
OUT
1
⋅
4 BW
⋅
=22 μF, ESR<1 mΩ, the type
,
C
4
=
22nF
,
C
5
=
L7986TA
220pF
LC
):