SiC462

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Vishay Siliconix

S17-0360-Rev. D, 13-Mar-17

7

Document Number: 65124

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

OPERATIONAL DESCRIPTION

Device Overview

SiC462 is a high-efficiency synchronous buck regulator

capable of delivering up to 6 A continuous current. The

device has programmable switching frequency of 100 kHz

to 2 MHz. The control scheme is based on voltage mode

constant on time. It delivers fast transient response and

minimizes external components. It also enables loop

stability regardless of the type of output capacitor used,

including low-ESR ceramic capacitors. This device also

incorporates a power saving feature by enabling diode

emulation mode and frequency fold back as the load

decreases.

SiC462 has a full set of protection and monitoring features:

• Over current protection in pulse-by-pulse mode

• Output overvoltage protection

• Output undervoltage protection with device latch

• Over temperature protection with hysteresis

• Dedicated enable pin for easy power sequencing

• Power good open drain output

• This device is available in MLP55-27L package to deliver

high power density and minimize PCB area.

Power Stage

SiC462 integrates a high-performance power stage with a

25 m

 n-channel high side MOSFET and a 11 m n-channel

low side MOSFET. The MOSFETs are optimized to achieve

up to 98 % efficiency.



as low as 4.5 V for power conversion.

Control Scheme

SiC462 employs a voltage - mode COT control mechanism

in conjunction with adaptive zero current detection which

allows precise power saving feature. The switching



0.8 V reference inputs to the error amplifier. An internally

generated for a fixed time, programmed by the external

be turned ON. Once the ON-time pulse expires, the high

side MOSFET is turned off and the low side MOSFET will be

turned ON after a break-before-make period. The low side

MOSFET will be on for duration of minimum OFF-time pulse

Fig. 4 illustrates the basic block diagram for voltage mode

constant on time architecture with external ripple injection.

• The reference of a basic voltage mode COT regulator is

replaced with a high gain error amplifier loop. This loop

ensures the DC component of the output voltage follows

the internal accurate reference voltage provides excellent

regulation

injection scheme ensures rapid correction of the transient

perturbation

• This establishes two parallel voltage regulating feedback

paths, a ripple injection path, and a steady accurate dc

reference path

Fig. 4 - SiC462 Control Block Diagram



For stability purposes the SiC462 requires 200 mV of ripple

ripple injection.



Fig. 5 demonstrates the basic operational waveforms:

Fig. 5 - SiC462 Operational Principle



In this case, set

 1 nF, R

above.

R

fsw

V

OUT

f

sw

190

10

12

–





---------------------------------------------

=

48

V1

Q1

Q2

Ripple based

controller

C

Y

R

COMP

1 nF

X1

C

COMP

+

Ref.

Erroramp

R

X

C

X

L

OUT

R1

R2

C

OUT

Load

R

X

V

 x V

f

SW



x C





=

Fixed on-time

V

RAMP

V

COMP

PWM

R

L

=