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 2004 Semtech Corp.

www.semtech.com

SC1592

POWER MANAGEMENT

Application Information

The SC1592 is a 3A low dropout high performance linear

voltage regulator. The SC1592 can be used for voltage

applications as low as 0.8V and is ideal for down

conversion utilizing dual supply configuration. This allows

for extremely low dropout voltages with excellent load

and line regulation. The SC1592 can be utilized in high

voltage applications, with V

there is adequate thermal management.

SC1592 is designed to meet stringent requirements of

current generation microprocessors and other sensitive

electronic devices. This is possible by employing an

additional bias source, V

needs to be at least 1.5V greater than the output voltage

in order to achieve low dropout, typically less then

300mV.

Unlike most of the other high current linear regulators,

the SC1592 provides a programmable current limit which

can be set with a single resistor. The value of the

programming resistor is:

LIM

OUT

LIM

R

V

240

I

•

≈

where I

V

R

The SC1592 has a fast transient response that allows it

to handle large load changes associated with high current

applications. Proper selection of the of the output

capacitor and it’s ESR value determines stable operation

and optimizes performance.

The typical application shown in Figure 2 was tested with

a wide range of different capacitors. The circuit was found

to be unconditionally stable with capacitor values from

47µF to 330µF and ESR ranging from 0.5m

Ω to greater

then 75m

Ω.

It’s recommended to maintain 5-10mA through the output

divider network in order to have a tight load and line

regulation. Initial accuracy of the internal voltage

reference V

This commands the use of 0.5% or better accuracy

resistors to build a precision power supply.

C1

2.2uF

C2

22uF

R1

C3

100uF

R3

R2

+1.8V Vout

+3.3V Vcntl

+2.5V Vin

SC1592

CNTL

IN

OUT

SENSE

ILIM

EN

GND

10k

66.5

53

100

Figure 2

The circuit in Figure 2 shows a typical application of 2.5V

to 1.8V conversion with a 3.3V control supply and the

load range of up to 3A steady state. Considering the

approximate 2W power being dissipated by the pass

element of the SC1592, we are still able to choose an

SO-8 EDP package with T

1sq.in. copper pad allocated for adequate heat transfer.

The ambient temperature in this case should not exceed

50°C. If this temperature range is too restrictive, then

the DDPAK can be utilized, having T

on the same size copper pad.

Input capacitor: A minimum of 10µF ceramic capacitor

is recommended to be placed directly next to the Vin pin.

This allows for the device being some distance from any

bulk capacitance on the rail. Additionally, bulk

capacitance may be added closely to the input supply

pin of the SC1592 to ensure that Vin does not sag,

improving load transient response.

Output capacitor: A minimum bulk capacitance of 33µF,

along with a 0.1µF ceramic decoupling capacitor is

recommended. Increasing the bulk capacitance will

improve the overall transient response. The use of

multiple lower value ceramic capacitors in parallel to

achieve the desired bulk capacitance will not cause

stability issues. Although designed for use with ceramic

output capacitors, the SC1592 is extremely tolerant of

output capacitor ESR values and thus will also work

comfortably with tantalum output capacitors.

.

typ

V

8

.

0

V

V

)

3

R

2

R

1

(

V

REF

REF

OUT

=

•

+

=