NSC LM3880MFX-1AD, LM3880 Datasheet

March 2007

LM3880
Power Sequencer

General Description

The LM3880 Power Sequencer offers the easiest method to
control power up and power down of multiple power supplies
(switchers or linear regulators). By staggering the startup se­quence, it is possible to avoid latch conditions or large in-rush
currents that can affect the reliability of the system.

Available in a SOT23-6 package, the Power Sequencer con­tains a precision enable pin and three open drain output flags.
Upon enabling the LM3880 the three output flags will sequen­tially release, after individual time delays, permitting the con­nected power supplies to startup. The output flags will follow
a reverse sequence during power down to avoid latch condi­tions.

Standard timing option of 30ms is available.
EPROM capability allows every delay and sequence to be

fully adjustable. Contact National Semiconductor if a non­standard configuration is required.

Features

■

Easiest method to sequence rails

■

Power up and power down control

■

Input voltage range of 2.7V to 5.5V

■

Small footprint SOT23-6

■

Low quiescent current of 25 µA

■

Standard timing options available

■

Customization of timing and sequence available through
factory programmability

Applications

■

Multiple supply sequencing

■

Microprocessor / Microcontroller sequencing

■

FPGA sequencing

Typical Application Circuit

20192601

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LM3880 Power Sequencer

Connection Diagram

20192602

Top View

SOT23–6 Package

Pin Descriptions

Pin # Name Function

1 VCC Input supply

2 GND Ground

3 EN Precision enable pin

4 FLAG3 Open drain output #3

5 FLAG2 Open drain output #2

6 FLAG1 Open drain output #1

Ordering Information

20192603

Sequence Designator Table

Sequence Number Flag Order

Power Up Power Down

1 1 - 2 - 3 3 - 2 - 1

2 1 - 2 - 3 3 - 1 - 2

3 1 - 2 - 3 2 - 3 - 1

4 1 - 2 - 3 2 - 1 - 3

5 1 - 2 - 3 1 - 3 - 2

6 1 - 2 - 3 1 - 2 - 3

See timing diagrams for more information

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LM3880

Timing Designator Table

Timing

Designator

t

d1

t

d2

t

d3

t

d4

t

d5

t

d6

AA 10ms 10ms 10ms 10ms 10ms 10ms

AB 30ms 30ms 30ms 30ms 30ms 30ms

AC 60ms 60ms 60ms 60ms 60ms 60ms

AD 120ms 120ms 120ms 120ms 120ms 120ms

See timing diagrams for more information

LM3880 Ordering Information

Order

Number

Timer settings Sequence

Order

Supplied As

Package

Type

NSC
Package
Drawing

Package

Marking

t

d1

t

d2

t

d3

t

d4

t

d5

t

d6

LM3880

MF-1AA

10ms 10ms 10ms 10ms 10ms 10ms 1 1k units T&R

SOT23-6 MF06A

F20A

LM3880

MFX-1AA

10ms 10ms 10ms 10ms 10ms 10ms 1 3k units T&R F20A

LM3880

MF-1AB

30ms 30ms 30ms 30ms 30ms 30ms 1 1k units T&R F21A

LM3880

MFX-1AB

30ms 30ms 30ms 30ms 30ms 30ms 1 3k units T&R F21A

LM3880

MF-1AC

60ms 60ms 60ms 60ms 60ms 60ms 1 1k units T&R F22A

LM3880

MFX-1AC

60ms 60ms 60ms 60ms 60ms 60ms 1 3k units T&R F22A

LM3880

MF-1AD

120ms 120ms 120ms 120ms 120ms 120ms 1 1k units T&R F23A

LM3880

MFX-1AD

120ms 120ms 120ms 120ms 120ms 120ms 1 3k units T&R F23A

Non-standard parts are available upon request. Please contact National Semiconductor for more information.

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LM3880

Absolute Maximum Ratings (Note 1)

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

VCC −0.3V to +6.0V
EN, FLAG1, FLAG2, FLAG3 −0.3V to 6.0V
Max Flag 'ON' Current 50 mA
Storage Temperature Range −65°C to +150°C
Junction Temperature 150°C
Lead Temperature (Soldering, 5

sec.) 260°C
Minimum ESD Rating ±2 kV

Operating Ratings (Note 1)

VCC to GND 2.7V to 5.5V
EN, FLAG1, FLAG2, FLAG3 −0.3V to VCC + 0.3V

Junction Temperature −40°C to +125°C

Electrical Characteristics Specifications with standard typeface are for T

J

= 25°C, and those in bold face type
apply over the full Operating Temperature Range (TJ = -40°C to +125°C). Minimum and Maximum limits are guaranteed through
test, design or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C and are provided for
reference purposes only. Unless otherwise specified VCC = 3.3V.

Symbol Parameter Conditions Min

(Note 3)

Typ

(Note 4)

Max

(Note 3)

Unit

I

Q

Operating Quiescent current 25 80 µA

Open Drain Flags

I

FLAG

FLAGx Leakage Current V

FLAGx

= 3.3V 1 20 nA

V

OL

FLAGx Output Voltage Low I

FLAGx

= 1.2mA 0.4 V

Power Up Sequence

t

d1

Timer delay 1 accuracy -15 15 %

t

d2

Timer delay 2 accuracy -15 15 %

t

d3

Timer delay 3 accuracy -15 15 %

Power Down Sequence

t

d4

Timer delay 4 accuracy -15 _ 15 %

t

d5

Timer delay 5 accuracy -15 15 %

t

d6

Timer delay 6 accuracy -15 15 %

Timing Delay Error

(t

d(x)

– 400 us) / t

d(x+1)

Ratio of timing delays For x = 1 or 4 95 105 %

t

d(x)

/ t

d(x+1)

Ratio of timing delays For x = 2 or 5 95 105 %

ENABLE Pin

V

EN

EN pin threshold 1.0 1.25 1.4 V

I

EN

EN pin pull-up current VEN = 0V 7 µA

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but does not guarantee specific performance limits. For guaranteed specifications and conditions, see the Electrical Characteristics.

Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.

Note 3: Limits are 100% production tested at 25°. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control

(SQC) methods. The limits are used to calculate National's Average Outgoing Quality Level (AOQL).

Note 4: Typical numbers are at 25°C and represent the most likely parametric norm.

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LM3880