A6986I datasheet(27/62 Pages) STMICROELECTRONICS

Part #	A6986I

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

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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6.5

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 (see Section 3 ) 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 A6986I 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. Bode plot (phase).

Figure 29. Bode plote (magnitude)

A6986I

Compensation network design

DS13481 - Rev 2

page 27/62

A6986I Datasheet(PDF) 27 Page - STMicroelectronics