L7986TA STMicroelectronics, L7986TA Datasheet - Page 24

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

Specifications of L7986TA

• Low Dropout Operation: 100% duty cycle

Application informations
6.4.2
24/43
Type II compensation network
If the equivalent series resistance (ESR) of the output capacitor introduces a zero with a
frequency lower than the desired bandwidth (that is: 2π∗ESR∗COUT>1/BW), this zero helps
stabilize the loop. Electrolytic capacitors show not negligible ESR (>30 mΩ), so with this
kind of output capacitor the type II network combined with the zero of the ESR allows
stabilizing the loop.
In
Figure 12. Type II compensation network
The singularities of the network are:
In
and the open loop gain (G
Figure 12
Figure 13
the type II network is shown.
the Bode diagram of the PWM and LC filter transfer function (G
f
Z1
=
----------------------------- -
2π R
LOOP
⋅
Doc ID 022098 Rev 1
1
4
(f) = G
⋅
C
4
,
PW0
f
P0
· G
=
LC
0
,
(f) · G
f
P1
TYPEII
=
------------------------------------------- -
2π R
⋅
(f)) are drawn.
4
⋅
1
------------------- -
C
C
4
4
+
⋅
C
C
5
5
PW0
· G
L7986TA
LC
(f))