L6986I datasheet(8/60 Pages) STMICROELECTRONICS

Part #	L6986I

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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Functional description

The iso-buck topology based on the L6986I consists of:

•

Primary side, the regulation loop of the peak current mode architecture regulates the primary voltage (blue

area in the picture below)

•

A two-windings transformer (in grey)

•

The secondary side, which generates the isolated output voltage (in green) given the selected transformer

ratio

Figure 4. Iso-buck general schematic

4.1

Primary side

The L6986I is based on a “peak current mode”, constant frequency control. The intersection between the error

amplifier output and the sensed inductor current generates the PWM control signal to drive the power switch of

the primary side, defining so the duty-cycle and regulating the primary output voltage.

The device operates in forced PWM control (MLF pin to GND), allowing negative currents to flow in the

synchronous MOSFET, hence transferring energy to the secondary coil during the off-time.

The main internal blocks shown in the block diagram in figure below are:

L6986I

Functional description

DS13647 - Rev 2

page 8/60

L6986I Datasheet(PDF) 8 Page - STMicroelectronics