SC1456-3.0IMSTR Ver la hoja de datos (PDF) - Semtech Corporation

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Fabricante

SC1456-3.0IMSTR

Dual 150mA Ultra Low Dropout, Low Noise Regulator

Semtech Corporation 

SC1456

POWER MANAGEMENT

Typical Characteristics (Cont.)

Sense/Select Threshold vs.

Junction Temperature

80

VIN = 3.6V

70

60

50

Output Spectral Noise Density

vs. Frequency

10

SC1456B

VIN = 3.6V

IOUT = 50mA

TJ = 25°C

1

COUT = 1µF

40

0.1

30

20

-50

-25

0

25

50

75

100

125

TJ (°C)

0.01

0.1

COUT = 100µF

1

10

100

f (kHz)

Applications Information

Theory Of Operation

The SC1456 is intended for applications where very low

dropout voltage, low supply current, low output noise and

pcb real estate are critical. It provides a very simple, low

cost solution for two seperate regulated outputs.

Internally preset output voltage options require the use

of only four external capacitors for operation.

Each regulator has both fixed and adjustable

output voltage modes. Grounding the SET pin (pulling it

below the Sense/Select threshold of 55mV) will connect

the internal resistor divider of that regulator to the error

amplifier resulting with the internally preset output

voltage. If SET is pulled above this threshold, then the

Sense/Select switch will connect the SET pin to the

error amplifier. The output will be regulated such that

the voltage at SET will equal VSET, the SET reference

voltage (typically 1.250V).

series resistance (ESR) of <1Ω over temperature.

Ceramic capacitors are ideal for this application.

Increasing the bulk capacitance will further reduce

output noise and improve the overall transient response.

Input capacitor: Semtech recommends the use of a 1µF

ceramic capacitor at each input. This allows for the

device being some distance from any bulk capacitance

on the rail. Additionally, input droop due to load transients

is reduced, improving load transient response.

Component Selection - Externally Set Output

Please refer to Figure 1 on page 9. The output voltage of

both outputs (OUT1 shown here) can be externally

adjusted anywhere within the range from 1.25V to

(V - V ). The output voltage will be in accordance

IN(MIN) D(MAX)

with the following equation:

An active high enable pin (EN) is provided for each

output to allow the customer to shut down that

regulator and enter an extremely low power Off-state. A

logic Low signal will reduce the regulator’s supply current

to 0.1nA.

Component Selection - General

Output capacitor: Semtech recommends a minimum

capacitance of 1µF at each output with an equivalent

VOUT

= 1.250 • 1+



R1

R2





1% tolerance resistors are recommended. The values of

R1 and R2 should be selected such that the current flow

through them is ≥ 10µA (thus R2 ≤ 120kΩ). At high input

voltages and/or high output currents, stability may be

improved by increasing C2 to 2.2µF and reducing R2 to

10kΩ. See “Component Selection - General” for input

capacitor requirements.

 2005 Semtech Corp.

8

www.semtech.com

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