L5986 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L5986' PDF : 39 Pages View PDF
L5986 - L5986A
Application information
Equation 21
R3
=
-----------R----1----------- ,
4-----⋅---B-----W---- – 1
fLC
C3
=
-------------------1---------------------
2π ⋅ R3 ⋅ 4 ⋅ BW
The suggested maximum system bandwidth is equals to the switching frequency divided by
3.5 (FSW/3.5), anyway lower than 100 kHz if the FSW is set higher than 500 kHz.
For example with VOUT = 3.3 V, VIN = 12 V, IO = 2.5 A, L=12μH, COUT = 22 μF, ESR < 1 mΩ,
the type III compensation network is:
R1 = 4.99kΩ, R2 = 1.1kΩ, R3 = 180Ω, R4 = 3.9kΩ, C3 = 3.3nF, C4 = 10nF, C5 = 150pF
In Figure 11 is shown the module and phase of the open loop gain. The bandwidth is about
71 kHz and the phase margin is 48°.
21/39
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