L6986ITR datasheet(26/60 Pages) STMICROELECTRONICS

Part #	L6986ITR

Description	38 V, 5 W synchronous iso-buck converter for isolated applications

PDF	60 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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5.5

Compensation network design

The maximum bandwidth of the system can be designed up to fSW/6 up to 150 kHz maximum to guarantee a valid

small signal model

RC= 2∙π∙BW∙COUT∙VOUT

0.85V∙gCS∙gm_typ

(20)

where:

fPOLE= ωP2∙π

(21)

ωP is defined by eq. (9) , gCS represents the current sense transconductance and gm TYP the error amplifier

transconductance.

CC= 52∙π∙RC∙BW

(22)

Example 1:

VIN = 12 V, VOUT_pri = 5.3 V, ROUT_pri = 5.6 Ω (corresponding to almost 1 A load).

Selecting the L6986I with VOUT_pri = 5.3 V, fSW = 500 kHz, Lpri = 18 µH, COUT_pri = 10 µF and ESR = 3 mΩ, RC

= 56 kΩ, CC = 680 pF, CP = 4.7 pF (please refer to Table 11), the gain and phase bode diagrams are plotted

respectively in Figure 29 and Figure 30.

Figure 29. Bode plote (magnitude)

Figure 30. Bode plot (phase)

L6986I

Compensation network design

DS13647 - Rev 1

page 26/60

L6986ITR Datasheet(PDF) 26 Page - STMicroelectronics