Datasheet L1581T, L1581S-3.3, L1581S-2.5, L1581S, L1581-3.3 Datasheet (NIKO)

1

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

GENERAL DESCRIPTION

The L1581 is a positive and very low
dropout voltage regulator with 5A output
current capability. When supplying 2.5V or

2.8V on Motherboards or VGA Card where
both 5V and 3.3V supplies are available,
the superior dropout characteristics of the
L1581 result in reduced heat dissipation
compared to regular LDOs, thus allowing
heat sink reduction. The adjustable version
requires only two external resistors to set
the output. The L1581 features a low
dropout of less than 600mV and offers fast
transient response, remote sense, internal
limiting, thermal shutdown and safe
operating area protection of the output
device.
The L1581 is a five terminal adjustable
voltage regulator available in the popular 5
pin TO-220 and TO-263 packages.

FEATURES

z Low dropout voltage 600mV at rated load

current

z Remote sense operation
z Fast transient response
z 0.5% voltage reference initial accuracy
z Standard 5 terminal, Low cost TO-220

and TO-263 packages

APPLICATIONS

z 3.3V to 2.8V or 2.5V for Motherboards or

VGA Card

z Spilt plane microprocessor supplies
z Post regulator for switching supplies

TYPICAL APPLICATION

Adjustable Output Parts

(2)

Vin

C3

0.033uF

Vout

Iadj

Vo = Vref (1+R2/R1) + Iadj x R2

330uF

C4

L1581X

35

4

2

1

OUTVin

CTR'L

ADJ

SENSE

R2

C2

10uF

R1

C1

330uF

Vctrl

Vref

2

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

Fixed Output Parts

330uF

C4

Vctrl

L1581X-2.5

35

4

2

1

OUTVin

CTR'L

ADJ

SENSE

2.5V Vout

C1

330uF

C2

10uF

Vin

330uF

C4

Vctrl

L1581X-3.3

35

4

2

1

OUTVin

CTR'L

ADJ

SENSE

C2

10uF

C1

330uF

Vin

3.3V Vout

NOTES :

(1) If the same voltage is input to both INPUT and CONTROL, then the dropout voltage will become 1.3V

maximum.

(2) A small (~0.033uF) capacitor can be used to bypass the ADJUST pin to improve transient response, if needed.

(3) Capacitor values are for reference only. Good quality, low ESR tantalum or aluminum electrolytic capacitors

should be used. Increasing the value of the output capacitor will improve the overall transient response.

3

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

ABSOLUTE MAXIMUM RATINGS

z Input Supply Voltage, V

IN

Control Input Voltage, V

CTRL

7V

13.2V

z Operating Junction
Temperature Range, TJ

0 to 125 °C

z Power Dissipation, PD

Internally

Limited

z Storage Temperature
Range, T

STG

-40 to 150 °C

z Thermal Resistance
Junction to Case, θJC

3 °C/W

z Lead Temperature, T

LEAD

(Soldering, 10 Seconds)

260 °C

z Thermal Resistance
Junction to Ambient, θJA

60 °C/W

ELECTRICAL CHARACTERISTICS (

Unless otherwise specified, TJ = 25 °C)

Parameter Symbol Test Conditions Typical Limits

V

CTRL

=4.5V, VIN=2.05V, I

OUT

=10mA 1.237V~1.263V

Reference Voltage

(1)

(Adj. Voltage
Versions)

V

REF

V

CTRL

= 4.5V, 10mA < I

OUT

< 5A,

VIN = 2.05V

1.25V
1.231V~1.269V

Dropout Voltage

(1) (2)

Minimum VIN

VI - VO

V

CTRL

= 4.75V, I

OUT

= 5A

0.54V 0.62V (Max)

V

CTRL

= 5V, V

IN

= V

OUT

＋ 0.8V,

I

OUT

=10mA

± 1%

Output Voltage

(1)

(Fixed Voltage
Versions)

V

OUT

V

CTRL

= 5V, 10mA < I

OUT

< 5A,

V

IN

= V

OUT

＋ 0.8V

V

OUT

± 1.5%

Line Regulation

(1)

REG

(LINE)

V

CTRL

= 4.5V to 12V, VIN = (V

OUT

＋

0.8V) to 5.5V, I

OUT

= 10mA

1.0mV 3.0mV

Load Regulation REG

(LOAD)

V

CTRL

= 4.5V, VIN = (V

OUT

＋0.8V) ,

I

OUT

= 10mA ~ 5A

1.0mV 5.0mV

Thermal Regulation

(6)

REG

(Thermal)

0.002

% / W

0.02% / W

Minimum Load
Current

(4)

IO

V

CTRL

= 5V, VIN = V

OUT

＋0.8V

5mA 10mA

Adjust Pin Current I

ADJ

V

CTRL

= 4.5V, VIN = V

OUT

＋0.8V,

I

OUT

= 10mA

50µA 120µA

Control Pin Current

(3)

I

CTRL

V

CTRL

= 4.5V, VIN = V

OUT

＋0.8V,

I

OUT

= 5A

33mA 120mA

Current Limit ICL

V

CTRL

= 4.5V, VIN = V

OUT

＋0.8V

Δ

V

OUT

= 100mV

5.1A (Min)

Ripple Rejection
Ratio

(5)

RA

V

CTRL

= VIN = 5V, I

OUT

= 5A

80dB 60dB (Min)

4

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

NOTE :

(1) Low duty cycle pulse testing with Kelvin connections required.
(2) Minimum input to output voltage differential required to maintain 1% regulation.
(3) Current used to drive the output section.
(4) Required to maintain regulation. Resistor divider R1, R2 is usually utilized for minimum load current.
(5) V

RIPPLE = 1VPK-PK, 120Hz.

(6) 30ms.

DEVICE SELECTION GUIDE

Device

L1581S L1581S-2.5 L1581S-3.3 L1581T L1581T-2.5 L1581-3.3

Package

TO-263 TO-263 TO-263 TO-220 TO-220 TO-220

Marking

L1581S L1581S-2.5 L1581S-3.3 L1581T L1581T-2.5 L1581-3.3

PIN CONFIGURATIONS

Pin # Function

1 Sense
2 Adjust
3 Output
4 Control
5 Input

Note: TAB is Output Pin

5

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

PIN FUNCTIONS

NO FUNCTION DESCRIPTION

1 Sense

This pin is the positive side of the reference voltage for the device. With
this pin it is possible to Kelvin sense the output voltage at the load.

2

Adjust

This pin is the negative side of the reference voltage for the device.
Transient response can be improved by adding a small bypass capacitor
from the adjust pin to ground.

3 Output

This is the power output of the device, and is electrically connected to
the TAB.

4 Control

This pin is the supply pin for the control circuitry for the device. The
current flow into this pin will be approximately 1% of the output. For the
device to regulate, the voltage at this pin must be between 1.0V and 1.3V
greater than the output voltage (see dropout specifications).

5 Input

This is the collector input to the power device of the L1581. The output
load current is supplied through this pin. For the device to regulate, the
voltage on this pin must be between 0.1V and 0.7V greater than the
output, depending upon load current (see dropout specifications).

6

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

TO-220 (5-Lead) MECHANICAL DATA

mm mm

Dimension

Min. Typ. Max.

Dimension

Min. Typ. Max.

A 9.78 10.16 10.54 H 1.57 1.7 1.83

B 2.61 2.74 2.87 I 6.81

C J 4.4 4.6 4.8

D 28.5 28.9 29.3 K 1.14 1.27 1.4

E 14.6 15.0 15.4 L 2.3 2.6 2.9

F 8.4 8.8 9.2 M 0.26 0.46 0.66

G 0.73 0.83 0.93 N

7°

7

Dual Input Ultra Low Dropout

Voltage Regulator (ULDO)

L1581 Series

TO-220,TO-263

JAN-08-Y02

NIKO-SEM

TO-263 (D2PAK, 5-Lead) MECHANICAL DATA

mm mm

Dimension

Min. Typ. Max.

Dimension

Min. Typ. Max.

A 14.5 15 15.8 H 1.0 1.5 1.8

B 4.2 4.7 I 9.8 10.3

C 1.20 1.35 J 6.5

D 2.8 K 1.5

E 0.3 0.4 0.5 L 0.7 0.85 1.0

F -0.102 0.203 M 1.57 1.7 1.83

G 8.5 9 9.5 N