Datasheet LX1431IM, LX1431IDM, LX1431CM, LX1431CDM Datasheet (Microsemi Corporation)

LIN DOC #:

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ROGRAMMABLE REFERENCE

1431

LX1431

THE INFINITE POWER OF INNOVATION

DESCRIPTION KEY FEATURES

The LX1431 is an adjustable shunt voltage
regulator featuring 100mA sink capability, a

0.4% initial reference voltage tolerance and
a 0.3% typical temperature stability. This
product, which is ideal for use in Pentium
applications, is equipped with on-chip di­vider resistors, enabling it to be configured
as a 5V shunt regulator. In this configura­tion, the LX1431 has an initial voltage toler­ance of only 1% and requires no additional
external components. The Linfinity
LX1431EB evaluation board and design kit
is available to assist engineers in quickly
configuring the most efficient, cost-effective
Pentium designs.

The output voltage of the LX1431 may be
set to any value between 2.5V and 36V
through the addition of two external resis­tors, which is of particular importance in the

design of both adjustable and switching
power supplies. In addition, the nominal
internal current limit of 100mA may be de­creased with the addition of a single exter-

®

nal resistor.

For applications requiring an adjustable
reference, the Linfinity LX6431CLP, a simpli­fied three-pin programmable reference, may
be used. Because the LX6431 is pin-for-pin
compatible with Linfinity's earlier TL431, use
of this product provides designers a simple
migration path to the more robust LX6431.
A separate LX6431 data sheet is available
which details the specifics of this product.

In addition, Pentium designers may use
Linfinity's LX8585/8585A 4.6A or LX8584/
8584A 7A Low Dropout Regulators to achieve
the most optimum motherboard configura­tion.

PRODUCT HIGHLIGHT

THE LX8584A AND LX1431 IN 75 AND 166MHZ P54C PROCESSOR APPLICATIONS USING 3.3V CACHE

5V

220µF
10V
Low ESR
from
Sanyo

V

IN

LX8584A

ADJ

0.1µF
50V

V

1

3

23

OUT

250pF

2

+V+V+

V

LX1431

SGND FGND

1kW

COL

0.01µF

1kW

1

8

REF

65

2.84kW

0.1%

330µF, 6.3V

Oscon Type

from Sanyo

1k

0.1%

P RODUCTION DATA SHEET

p GUARANTEED 0.4% INITIAL VOLTAGE

TOLERANCE

p 0.1Ω TYPICAL DYNAMIC OUTPUT

IMPEDANCE

p FAST TURN-ON

p SINK CURRENT CAPABILITY, 1mA TO 100mA
p LOW REFERENCE PIN CURRENT

APPLICATIONS

■ LINEAR REGULATORS

■ ADJUSTABLE POWER SUPPLIES

■ SWITCHING POWER SUPPLIES

■ LX1431EB EVALUATION BOARD FOR

PENTIUM APPLICATIONS AVAILABLE.
CONSULT FACTORY.

VO 7A

(See Table Below)

3x

Low ESR

21k
1%

JP1

PLACE IN µP SOCKET CAVITY

100µF x 6

10V

AVX TYPE

TPS

1µF x 10
SMD

µP

Load

Copyright © 1997
Rev. 1.2 4/97

V

O

JP1 TYPICAL APPLICATION

3.50 Short 120/166MHz, VRE, 3.3V Cache

3.38 Open 75/90/100/133MHz, STND, 3.3V Cache

PACKAGE ORDER INFORMATION

T

(°C)

A

Plastic DIP

M

8-pin

0 to 70 LX1431CM LX1431CDM

-40 to 85 LX1431IM LX1431IDM

Note: All surface mount packages are available in Tape & Reel.

Append the letter "T" to part number (i.e. LX1431CDMT).

FOR FURTHER INFORMATION CALL [phone]

11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841

Thick traces represent high current traces which
must be low resistance / low inductance traces in
order to achieve good transient response.

Plastic SOIC

DM

8-pin

1

LX1431

PRODUCT DATABOOK 1996/1997

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RODUCTION DATA SHEET

P

ABSOLUTE MAXIMUM RATINGS (Note 1)

V+, V

COLLECTOR

V

, R

COMP

GND-F to GND-S ........................................................................................................ 0.7V

................................................................................................................. 36V

, R

, V

TOP

MID

...................................................................................................... 6V

REF

Operating Junction Temperature

Plastic (M, DM Packages) ..................................................................................... 150°C

Storage Temperature Range ...................................................................... -65°C to 150°C

Lead Temperature ..................................................................................................... 300°C

Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect

to Ground. Currents are positive into, negative out of the specified terminal.

THERMAL DATA

M PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θ

θθ

JA

95°C/W

DM PACKAGE:

D

θθ

θ

θθ

x θ

JA

).

JA

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

Junction Temperature Calculation: T

numbers are guidelines for the thermal performance of the device/pc-board system.

The θ

JA

All of the above assume no ambient airflow.

= TA + (P

J

165°C/W

BLOCK DIAGRAM

R

TOP

+

V

COMP COLLECTOR

PACKAGE PIN OUTS

COLLECTOR

COLLECTOR

COMP

1 8

2 7

COMP

+

3 6

V

4 5

R

TOP

M PACKAGE

(Top View)

1 8

2 7

+

3 6

V

4 5

R

TOP

DM PACKAGE

(Top View)

REF
R

MID

GND-F
GND-S

REF
R

MID

GND-F
GND-S

REF

R

MID

432 1

5K

8

gm=
60µA/V

7

5K

2.5V

65

GND-SENSE GND-FORCE

2

Copyright © 1997

Rev. 1.2 4/97

PRODUCT DATABOOK 1996/1997

LX1431

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P RODUCTION DAT A SHEET

ELECTRICAL CHARACTERISTICS

(Unless otherwise specified, these specifications apply over the operating ambient temperatures for LX1431C with 0°C ≤ TA ≤ 70°C, LX1431I with -40°C ≤ TA ≤ 85°C.)

Parameter

Reference Voltage

Reference Drift ∆V
Voltage Ratio, Reference to Cathode ∆V

(Open Loop Gain) ∆V

Reference Input Current

Minimum Operating Current I

Off-State Cathode Current

Off-State Collector Leakage Current

Dynamic Impedance [Z

Collector Current Limit I

Symbol

V

REF

/∆TV

REF

REFIK

KA

[I

]

REF

MINVKA

]

[I

OFF

]

[I

LEAK

]VKA = V

KA

LIM

Test Conditions

VKA = 5V, IK = 2mA, TA = 25°C
VKA = 5V, IK = 2mA

= 5V, IK = 2mA

KA

= 2mA, VKA = 3V to 36V

VKA = 5V, TA = 25°C
VKA = 5V

= V

to 36V, TA = 25°C

REF

VKA = 36V, V
VKA = 36V, V

V

= 36V, V+ = 5V, V

COLL

V

= 36V, V+ = 5V, V

COLL

VKA = V

= 0V, TA = 25°C

REF

= 0V

REF

, I

= 1mA to 100mA, f ≤ 1kHz, T

REF

K

+ 50mV

REF

= 2.4V, TA = 25°C

REF

= 2.4V

REF

5V Reference Output Internal Divider Used, IK = 2mA, TA = +25°C

= 25°C

A

LX1431I

Min. Typ. Max. Min. Typ. Max.

2490 2500 2510 2490 2500 2510 mV
2465 2535 2480 2520 mV

50 30 ppm/°C

0.2 1.0 0.2 1.0 mV/V

0.2 1 0.2 1 µA

1.5 1.2 µA

0.6 1 0.6 1 mA
11µA

15 2 µA

11µA
52µA

0.1 0.1 Ω

80 360 100 360 mA

4950 5000 5050 4950 5000 5050 mV

LX1431C

Units

Copyright © 1997
Rev. 1.2 4/97

3

PRODUCT DATABOOK 1996/1997

LX1431

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RODUCTION DATA SHEET

P

APPLICATION INFORMATION

PIN FUNCTIONS

Pin 1 COLL: Open collector of the output transistor. The
maximum pin voltage is 36V. The saturation voltage at 100mA
is approximately 1V.

Pin 2 COMP: Base of the driver for the output transistor. This
pin allows additional compensation for complex feedback
systems and shutdown of the regulator. It must be left open if
unused.

Pin 3 V+: Bias voltage for the entire shunt regulator. The
maximum input voltage is 36V and the minimum to operate is
equal to V

Pin 4 R

guarantees 1% accuracy of operation as a 5V shunt regulator
with no external trim. The pin is tied to COLL for self­contained 5V operation. It may be left open if unused.

Pin 5 GND-S: Ground reference for the on-chip resistive
divider and shunt regulator circuitry except for the output
transistor. This pin allows external current limit of the output
transistor with one resistor between GND-F (force) and GND-S
(sense).

Pin 6 GND-F: Emitter of the output transistor and substrate
connection for the die.

Pin 7 R

between R
contained 5V operation. It may be left open if unused.

(2.5V). The quiescent current is typically 0.6mA.

REF

: Top of the on-chip 5k-5k resistive divider that

TOP

: Middle of the on-chip resistive divider string

MID

and GND-S. The pin is tied to REF for self-

TOP

, R

COMP, R

circuits that must not be activated on a continuous basis.

, and REF have static discharge protection

TOP

MID

Therefore, the absolute maximum DC voltage on these pins is
6V, well beyond the normal operating conditions.

As with all bipolar ICs, the LX1431 contains parasitic diodes
which must not be forward biased or else anomalous behavior
will result. Pin conditions to be avoided are RTOP below
RMID in voltage and any pin below GND-F in voltage (except
for GND-S).

FREQUENCY COMPENSATION

Excess capacitance on the REF pin can introduce enough
phase shift to induce oscillation when configured as a refer­ence >2.5V. This can be compensated with capacitance
between COLL and REF (phase lead). More complicated
feedback loops may require shaping of the frequency response
of the LX1431 with dominant pole or pole-zero compensation.
This can be accomplished with a capacitor or series resistor
and capacitor between COLL and COMP.

The compensation schemes mentioned above use voltage
feedback to stabilize the circuits. There must be voltage gain
at the COLL pin for them to be effective, so the COLL pin must
see a reasonable AC impedance. Capacitive loading of the
COLL pin reduces the AC impedance, voltage gain, and
frequency response, thereby decreasing the effectiveness of
the compensation schemes, but also decreasing their necessity.

Pin 8 REF: Control pin of the shunt regulator with a 2.5V
threshold.

4

Copyright © 1997

Rev. 1.2 4/97

PRODUCT DATABOOK 1996/1997

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P RODUCTION DAT A SHEET

GRAPH / CURVE INDEX

Characteristic Curves

FIGURE #

1. COLLECTOR V

2. COMPENSATION PIN VOLTAGE vs. TEMPERATURE vs. I

3. I

vs. TEMPERATURE WITH EXTERNAL RESISTOR

LIMIT

4. REFERENCE VOLTAGE and REFERENCE CURRENT vs. V+

5. REFERENCE VOLTAGE and REFERENCE CURRENT vs. V+

6. 2.5V REFERENCE I

7. REFERENCE VOLTAGE and REFERENCE CURRENT vs. TEMPERATURE

vs. TEMPERATURE vs. CURRENT

SAT

vs. V

K

KA

COLL

LX1431

Copyright © 1997
Rev. 1.2 4/97

5

LX1431

(

REF

)

(

)

PRODUCT DATABOOK 1996/1997

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RODUCTION DATA SHEET

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CHARACTERISTIC CURVES

FIGURE 1. — COLLECTOR V

0.6

0.5

0.4

0.3

0.2

) Saturation Voltage - (V)

SAT

(V

0.1

0

-50 -25 0

(TA) Ambient Temperature - (°C)

FIGURE 3. — I

1.5

1.4

1.3

1.2

1.1

1

(Normalized)

0.9

LIMIT

I

0.8

0.7

0.6

0.5

-50 -25 0

vs. TEMPERATURE WITH EXTERNAL RESISTOR FIGURE 4. — REFERENCE VOLTAGE and

LIMIT

vs. TEMPERATURE vs. CURRENT

SAT

I

= 100mA

COLL

I

= 50mA

COLL

I

= 20mA

COLL

I

= 10mA

COLL

25

50 75 100 125

25

50 75 100 125

FIGURE 2. —

2.5

1.5

COMPENSATION PIN VOLTAGE
vs. TEMPERATURE vs. I

3

2

I

1

= 10mA

COLL

COLL

I

= 100mA

COLL

) Compensation Pin Voltage - (V)

0.5

COMP

(V

0

-50 -25 0

25

50 75 100 125

(TA) Ambient Temperature - (°C)

REFERENCE CURRENT vs. V+

2.505

2.504

2.503

I

2.9

REF

V

REF

3.1 3.3 3.5

2.502

2.501

2.50

2.499

2.498

) Reference Voltage - (V)

REF

2.497

(V

2.496

2.495

2.5 2.7

200

190

180

nA

170

160

150

140

130

120

Reference Current -

110

I

100

90

80

(TA) Ambient Temperature - (°C)

V+ (V)

6

Copyright © 1997

Rev. 1.2 4/97

PRODUCT DATABOOK 1996/1997

100

0

VKA - (V)

I

K

- (µA)

0 0.5 1.0 1.5 2.0 2.5 3.0

200

300

400

500

600

700

800

900

1000

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P RODUCTION DAT A SHEET

CHARACTERISTIC CURVES

LX1431

FIGURE 5. — REFERENCE VOLTAGE and

REFERENCE CURRENT vs. V+

2.502

2.501

2.50

2.499

2.498

2.497

2.496

2.495

2.494

) Reference Voltage - (V)

2.493

REF

(V

2.492

2.491

2.490
0 5

10

V

REF

15

20 25 40

V+ (V)

FIGURE 6. — REFERENCE VOLTAGE and

REFERENCE CURRENT vs. TEMPERATURE

I

REF

30 35

FIGURE 6. —

200

190

180

170

160

150

140

130

120

) Reference Current - (nA)

110

100

90

80

REF

(I

2.5V REFERENCE IK vs. V

KA

2.51

2.505

2.5

2.495

2.49

) Reference Voltage - (V)

REF

(V

2.485

2.48

-50 -25

0

(TA) Temperature - (°C)

Copyright © 1997
Rev. 1.2 4/97

V

REF

I

REF

25 75 125

50 100

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

) Reference Current - (nA)

-0.6

-0.8

-1

REF

(I

Pentium is a registered

trademark of Intel Corporation.

7