SC563 datasheet(12/16 Pages) SEMTECH

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SC563

General Description

The SC563 is a dual output linear regulator with low

dropout voltage, low supply current, and low output

noise. The device provides a simple, low cost solution with

minimal PCB area. It has a miniature package size and

needs four µF 0402 size external capacitors for its input

and output.

The dual LDOs are powered from separate input supply

pins. Each LDO provides up to 300mA output current.

Power On and Off Control and Turn-on Delay

The SC563 device has separate enable pins (EN and EN2)

that control the LDO outputs respectively. Pulling enable

pin high will enable the device when the Vin is above the

its UVLO level at about 2.4V. Pulling this pin low causes

the device to shutdown where it typically draws 00nA

from the input supply.

When the enable pins are connected to the input voltage

supply, the device turn-on and turn-off has two voltage

thresholds to overcome. At the turn-on event, the enable

pin voltage needs to be greater than the enable threshold

and the Vin voltage needs to be higher than the UVLO.

The higher of the two voltages, which is the UVLO,

determines the turn on time. At turn-off, the first

condition of either enable threshold low or the VIN UVLO

will determine the turn-off event.

After the enable goes high, the IC has a delay time before

the output voltage ramps up. The delay is typically

between 20µs to 50µs. The 50µs is related to the lower

Vin condition.

With uF output capacitor (capacitor part number:

GRM55R6A05kE5) at no load conditions, the output

voltage ramp time is typically at 5µs. The device has an

internal discharge MOSFET to discharge the output

voltage at disable, the typical discharge time is at 2ms.

The enable and disable waveforms are illustrated in Figure

and the Oscilloscope waveform is shown in the Typical

Characteristics.

The Output Noise

LDO’s noise generally is characterized through noise

spectral density (NSD) and total RMS value in the

frequency band between 0Hz to 00kHz. The noise

spectral density can be measured using a network

analyzer with active probes. The RMS noise value is

obtained from the noise spectral density curve by taking

the square root of the area within the frequency range

from 0Hz to 00kHz.

The normalized output noise for SC563 is at a typical

value of 00µVrms/V. The generalized output voltage

noise can be approximated by: V

rms=Vout*00 µV.

Protection Features

The SC563 provides protection features to ensure that no

damage is incurred in the event of a fault condition. These

functions include:

Under-Voltage Lockout

Over-Temperature Protection

Short-Circuit Protection with peak and fold-

back current limit

•

Applications Information

140-510

Enable

Vout

2ms

Figure 1 — Timing Diagram

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