National Semiconductor LP3881 Technical data

LP3881

0.8A Fast-Response Ultra Low Dropout Linear Regulators

LP3881 0.8A Fast-Response Ultra Low Dropout Linear Regulators

August 2003

General Description

The LP3881 is a high current, fast response regulator which can maintain output voltage regulation with minimum input to output voltage drop. Fabricated on a CMOS process, the device operates from two input voltages: Vbias provides voltage to drive the gate of the N-MOS power transistor, while Vin is the input voltage which supplies power to the load. The use of an external bias rail allows the part to operate from ultra low Vin voltages. Unlike bipolar regulators, the CMOS architecture consumes extremely low quiescent current at any output load current. The use of an N-MOS power transistor results in wide bandwidth, yet minimum external capacitance is required to maintain loop stability.

The fast transient response of these devices makes them suitable for use in powering DSP, Microcontroller Core voltages and Switch Mode Power Supply post regulators. The parts are available in TO-220 and TO-263 packages.

Dropout Voltage: 75 mV (typ) Ground Pin Current: 3 mA (typ) at full load. Shutdown Current: 60 nA (typ) when S/D pin is low. Precision Output Voltage: 1.5% room temperature accu-

racy.

0.8A load current.

Typical Application Circuit

Features

n Ultra low dropout voltage (75 mV@0.8A typ) n Low ground pin current n Load regulation of 0.04%/A n 60 nA typical quiescent current in shutdown n 1.5% output accuracy (25˚C) n TO-220, TO-263 packages n Over temperature/over current protection n −40˚C to +125˚C junction temperature range

Applications

n DSP Power Supplies n Server Core and I/O Supplies n PC Add-in-Cards n Local Regulators in Set-Top Boxes n Microcontroller Power Supplies n High Efficiency Power Supplies n SMPS Post-Regulators

At least 4.7 µF of input and output capacitance is required for stability.

20063001

Connection Diagrams

TO-220, Top View

20063002

TO-263, Top View

20063003

Ordering Information

LP3881

Order Number Package Type Package Drawing Supplied As

LP3881ES-1.2 TO263-5 TS5B Rail

LP3881ESX-1.2 TO263-5 TS5B Tape and Reel

LP3881ET-1.2 TO220-5 T05D Rail

LP3881ES-1.5 TO263-5 TS5B Rail

LP3881ESX-1.5 TO263-5 TS5B Tape and Reel

LP3881ET-1.5 TO220-5 T05D Rail

LP3881ES-1.8 TO263-5 TS5B Rail

LP3881ESX-1.8 TO263-5 TS5B Tape and Reel

LP3881ET-1.8 TO220-5 T05D Rail

Block Diagram

20063024

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LP3881

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Storage Temperature Range −65˚C to +150˚C

(Survival) Internally Limited

OUT

Output Voltage (Survival) −0.3V to +6V

Junction Temperature −40˚C to +150˚C

Operating Ratings

Lead Temp. (Soldering, 5 seconds) 260˚C

ESD Rating

Human Body Model (Note 3) Machine Model (Note 10)

2kV

200V

Power Dissipation (Note 2) Internally Limited

Supply Voltage (Survival) −0.3V to +6V

Supply Voltage (Survival) −0.3V to +7V

BIAS

VINSupply Voltage (V

Shutdown Input Voltage 0 to +6V

OUT

Operating Junction

Temperature Range

BIAS

Shutdown Input Voltage (Survival) −0.3V to +7V

Electrical Characteristics Limits in standard typeface are for T

over the full operating temperature range. Unless otherwise specified: V C

OUT

= 4.7 µF, V

S/D=VBIAS

Symbol Parameter Conditions

BIAS

0.8A

≤ 6V

∆V

Output Voltage Tolerance 10 mA<I

(NOM) + 1V ≤ VIN≤ 5.5V

4.5V ≤ V

/∆V

Output Voltage Line Regulation

VO(NOM) + 1V ≤ VIN≤ 5.5V

(Note 7)

∆VO/∆I

Output Voltage Load Regulation

10 mA<I

0.8A 0.04

(Note 8)

IQ(VIN) Quiescent Current Drawn from

Q(VBIAS

Dropout Voltage (Note 9) IL= 0.8A

Supply

) Quiescent Current Drawn from

Supply

BIAS

Short-Circuit Current V

10 mA

S/D

10 mA

S/D

OUT

0.8A

≤ 0.3V

0.8A

≤ 0.3V

= 0V 1.8 A

Shutdown Input

SDT

Output Turn-off Threshold Output = ON 0.7 1.3

Output = OFF 0.7 0.3

Td (OFF) Turn-OFF Delay R

Td (ON) Turn-ON Delay R

S/D

S/D Input Current V

LOAD

=1.3V 1

S/D

≤ 0.3V −1

S/D

OUT

<< <<

IN=VO

Td (OFF) 20

Td (ON) 15

OUT+VDO

) to 5.5V

0.8A

−40˚C to +125˚C

Supply Voltage 4.5V to 6V

= 25˚C, and limits in boldface type apply

(NOM) + 1V, V

Typical

(Note 4)

= 4.5V, IL= 10 mA, CIN=

BIAS

MIN

(Note 5)

1.198

MAX

(Note 5)

1.234

Units

1.216

1.186

1.478

1.246

1.522 V1.5

1.455

1.773

1.545

1.827

1.8

1.746

1.854

0.01 %/V

0.06

0.03

120

160

%/A

µA

µs

µA

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Electrical Characteristics Limits in standard typeface are for T

over the full operating temperature range. Unless otherwise specified: V

LP3881

OUT

= 4.7 µF, V

S/D=VBIAS

. (Continued)

IN=VO

= 25˚C, and limits in boldface type apply

(NOM) + 1V, V

= 4.5V, IL= 10 mA, CIN=

BIAS

Symbol Parameter Conditions

Typical

(Note 4)

MIN

(Note 5)

MAX

(Note 5)

AC Parameters

PSRR (V

BIAS

) Ripple Rejection for VINInput

Voltage

Ripple Rejection for V

)

Voltage

BIAS

VIN=V

OUT

VIN=V

OUT

BIAS=VOUT

+1V, f = 120 Hz

+ 1V, f = 1 kHz 65

+ 3V, f = 120 Hz

+ 3V, f = 1 kHz 65

Output Noise Density f = 120 Hz 1 µV/root−Hz

Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Operating ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications, see Electrical Characteristics. Specifications do not apply when operating the device outside of its rated operating conditions.

Note 2: At elevated temperatures, device power dissipation must be derated based on package thermal resistance and heatsink thermal values. θ devices is 65˚C/W if no heatsink is used. If the TO-220 device is attached to a heatsink, a θ approximately 40˚C/W if soldered down to a copper plane which is at least 1.5 square inches in area. If power dissipation causes the junction temperature to exceed specified limits, the device will go into thermal shutdown.

Note 3: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.

Note 4: Typical numbers represent the most likely parametric norm for 25˚C operation.

Note 5: Limits are guaranteed through testing, statistical correlation, or design.

Note 6: If used in a dual-supply system where the regulator load is returned to a negative supply, the output pin must be diode clamped to ground.

Note 7: Output voltage line regulation is defined as the change in output voltage from nominal value resulting from a change in input voltage.

Note 8: Output voltage load regulation is defined as the change in output voltage from nominal value as the load current increases from no load to full load.

Note 9: Dropout voltage is defined as the minimum input to output differential required to maintain the output with 2% of nominal value.

Note 10: The machine model is a 220 pF capacitor discharged directly into each pin. The machine model ESD rating of pin 5 is 100V.

Output Noise Voltage

= 1.8V

OUT

BW = 10 Hz − 100 kHz 150

BW = 300 Hz − 300 kHz 90

value of 4˚C/W can be assumed. θ

J-S

for TO-220

J-A

for TO-263 devices is

J-A

µV (rms)

Units

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