SC493 datasheet(12/28 Pages) SEMTECH

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SC493

General Description

The SC493 is a step down synchronous buck DC-DC

controller optimized for use in 3.3V/5V input small form-

factor applications. It has the following key features:

I2C control over output voltage offset, margin-

ing, power-on delay, switching frequency, soft-

start duration, and power save mode.

Integrated bootstrap switch

Programmable switching frequency from 250kHz

to 1MHz to optimize board space and efficiency.

Protection features — over-current, over-voltage,

under-voltage, and over-temperature

Power save operation — low quiescent current

and ultrasonic power save

Status and flag bits for diagnosis and protection

purposes

Supports 25A operation

I2C Compatible Interface Functions

The I2C interface can be used to read & write the following

functions:

Shutdown/Start-up of output

Power-on delay and soft-start duration

Output voltage offset and margining

Power save mode

Switching frequency

Additionally, the I2C interface can be used to read status

and flag bits for the following functions:

Under voltage

Over voltage

Over temperature

Current limit

Brown out

Did not start

Discontinuous mode

Power good

Status and Flag Bits

The status and flag bits are used to indicate the status of

the converter. The status bits always indicate the current

state of the converter — the status bit becomes high

when the specified condition happens and turns low

when the specified condition disappears. The flag bits also

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become high when the specified condition happens, but

will not turn low when the specified condition disappears.

For the above mentioned status and flag bits, only discon-

tinuous mode and power good are status bits, the rest of

them are all flag bits. The flag bits remain set until one of

the following events occurs:

The input voltage is cycled

EN pin is cycled

CLF bit is set

Enable/Disable

The converter is enabled by applying power to VDD

(VDD when used refers to AVDD and PVDD together) and

VIN, and pulling the EN pin high. The output voltage will

rise to the voltage programmed by the FB pin and the

external FB network. Pulling the EN pin low turns the

converter off and clears all flag bits. The converter can

also be turned on/off via the I2C interface. When the EN

pin is high, setting the ENSW bit low will turn off the

converter, but the flag bits will not be cleared. Setting the

ENSW bit back high will turn on the converter again.

Diagnosis and Protection Features

When the device detects fault conditions, the SC493 sets

the flag bits indicating what fault conditions have

occurred. In addition, depending upon what kind of faults

have been detected, the SC493 will provide appropriate

actions to safeguard the device from catastrophic failures.

The following paragraphs describe how these fault condi-

tions are handled by the SC493.

Did Not Start Indication

If the FB voltage does not rise to 90% of nominal voltage

after the converter is enabled, the soft-start duration has

passed, and the power good delay has elapsed, the Did

Not Start (DNS) flag bit is set. Note that the converter does

not latch off just because this bit is set.

Output Over Voltage Protection

When the FB pin voltage exceeds 120% of the nominal

voltage, DL goes high, forcing the low-side MOSFET on,

and the OVO flag bit is set. The low side MOSFET stays on

(and the high side MOSFET remains off) until the output

voltage comes back into regulation. However, the CLF bit

will successfully clear the OVO flag as soon as the FB falls

below 120% of the normal voltage. The converter does not

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Applications Information

SC493 Datasheet(PDF) 12 Page - Semtech Corporation

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