LX6431 / 6431A / 6431B
PRECISION PROGRAMMABLE REFERENCES
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KEY FEATURES
DESCRIPTION
The LX6431 series precision adjustable three
terminal shunt voltage regulators are pin-to-pin
compatible with the industry standard TL431, but
with significant improvements.
The LX6431
design has eliminated regions of instability
common to older generation shunt regulator
products like the TL431. Designs are made simpler
by eliminating the task of insuring capacitive loads,
and output voltage and cathode currents don’t
combine for unstable operation. The capacitor
value is chose simply to give the best load transient
response without the possibility of instability. A
lower reference input current allows the use of
higher value reference divider resistors, reducing
the current drain from batteries in portable
S
equipment as well as reducing the voltage
programming errors due to the impedance of the
divider network (See product Highlight)
In addition, the LX6431B has an improved
initial accuracy of 0.4%, and the output voltage is
programmable by using two external resistors
from 2.5V to 36V.
These devices offer low output impedance for
improved load regulation. The typical output
impedance of these devices is 100mΩ. The
reduced reference input bias current and minimum
operating currents make these devices suitable for
portable and micro power applications.
„ Unconditionally Stable for All
„
„
„
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„
Cathode To Anode Capacitance
Values
Reduced Reference Input
Current Allowing The Use of
Higher Value Divider Resistors
(0.5µA)
Initial Voltage Reference
Accuracy of 0.4% (LX6431B)
Sink Current Capability 0.6mA to
100mA
Typical Output Dynamic
Impedance Less Than 100mΩ
Adjustable Output Voltage From
2.5V to 36V
„
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
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Output Voltage Error Due to IREF
TA (°C)
0 to 70
-40 to 85
Initial
Tolerance
2%
1%
0.4%
2%
1%
0.4%
PK
PACKAGE ORDER INFO
Plastic TO-89
Plastic SOIC
DM 8-Pin
3-Pin
LP
Plastic TO-92
3-Pin
RoHS Compliant / Pb-free
Transition D/C: 0518
RoHS Compliant / Pb-free
Transition D/C: 0440
RoHS Compliant / Pb-free
Transition D/C: 0509
LX6431CPK
LX6431ACPK
LX6431BCPK
LX6431IPK
LX6431AIPK
LX6431BIPK
LX6431CDM
LX6431ACDM
LX6431BCDM
LX6431IDM
LX6431AIDM
LX6431BIDM
LX6431CLP
LX6431ACLP
LX6431BCLP
LX6431ILP
LX6431AILP
LX6431BILP
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX6431CDM-TR)
Copyright © 1999
Rev. 1.4a,2005-04-04
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
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LX6431 / 6431A / 6431B
PRECISION PROGRAMMABLE REFERENCES
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ABSOLUTE MAXIMUM RATINGS
D
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A T A
H E E T
PACKAGE PIN OUT
Cathode to Anode Voltage (VKA).................................................................... -0.3V to 37V
Reference Input Current (IREF) .....................................................................-50µA to 10µA
Continuous Cathode Current (IK)........................................................... -100mA to 150mA
Operating Temperature Range ................................................................................... 150°C
Maximum Operating Junction Temperature
Plastic (DM & LP Packages) ..................................................................................... 150°C
Storage Temperature Range.........................................................................-65°C to 150°C
Package Peak Temp. for Solder Reflow (40 seconds maximum exposure) ... 260°C (+0 -5)
CATHODE
1
8
REF
N.C.
2
7
ANODE
ANODE
3
6
ANODE
4
5
N.C.
N.C.
DM PACKAGE
(Top View)
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Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
Pin numbers refer to DIL packages only.
THERMAL DATA
1
CATHODE
2
ANODE
3
REF
LP PACKAGE
(Top View)
DM
Plastic SOIC 8-Pin
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
LP
165°C/W
Plastic TO-92 3-Pin
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
PK
REF
1
ANODE
2
CATHODE
3
156°C/W
Plastic TO-89 3-Pin
THERMALRESISTANCE-JUNCTION TO TAB, θJT
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
PK PACKAGE
35°C/W
71°C/W
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
(Top View)
N.C. – No Connection
RoHS / Pb-free 100% Matte Tin Lead Finish
SIMPLIFIED BLOCK DIAGRAM
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Cathode (K)
REF(R)
+
-
VREF
Anode (A)
Copyright © 1999
Rev. 1.4a,2005-04-04
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
2
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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ELECTRICAL CHARACTERISTICS
(Note 2)
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for LX6431C/LX6431AC/LX6431BC with 0°C ≤ TA ≤
70°C, LX6431I/LX6431AI/LX6431BI with -40°C ≤ TA ≤ 85°C.)
Parameter
Reference Input Voltage
LX6431
LX6431A
LX6431B
LX6431
VREF
Test Conditions
IK = 10mA, VKA = VREF, TA = 25°C,
IK = 10mA, VKA = VREF, TA = 25°C
IK = 10mA, VKA = VREF, TA = 25°C
IK = 10mA, VKA = VREF, 0°C ≤ TA ≤ 70°C
IK = 10mA, VKA = VREF, -40°C ≤ TA ≤ 85°C
IK = 10mA, VKA = VREF, 0°C ≤ TA ≤ 70°C
IK = 10mA, VKA = VREF, -40°C ≤ TA ≤ 85°C
IK = 10mA, VKA = VREF, 0°C ≤ TA ≤ 70°C
IK = 10mA, VKA = VREF, -40°C ≤ TA ≤ 85°C
IK = 10mA, VKA = 2.5V to 36V, TA = 25°C
IK = 10mA, VKA = 2.5V to 36V, TA = Operating Range
VKA = VREF, TA = 25°C
VKA = VREF, TA = Operating Range
VKA = VREF to 36V, TA = 25°C
VKA = VREF to 36V, TA = Operating Range
VKA = 36V, VREF = 0V, TA = 25°C
VKA = VREF, IK = 0.6mA to 100mA, f ≤ 1kHz, TA = 25°C
LX6431
Units
Min. Typ. Max.
2440
2470
2490
2550
2520
2510
15
25
15
25
15
20
1
1
0.5
0.5
0.6
0.6
1
100
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Reference Drift
Symbol
LX6431A
LX6431B
Voltage Ratio, Reference to Cathode
(Note 3)
Reference Input Current
IREF
Minimum Operating Current
IMIN
Off-State Cathode Current
Dynamic Impedance
IOFF
ZKA
0.3
0.3
0.1
0.1
0.4
0.4
0.3
30
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV/V
mV/V
µA
µA
mA
mA
µA
mΩ
Note 2. These parameters are guaranteed by design.
∆VREF
∆VKA
Ratio of change in reference input voltage
to the change in cathode voltage.
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Note 3.
Copyright © 1999
Rev. 1.4a
3
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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GRAPH / CURVE INDEX
FIGURE INDEX
Characteristic Curves
Application Information
FIGURE #
1.
REFERENCE VOLTAGE vs. FREE-AIR TEMPERATURE
7.
2.
REFERENCE CURRENT vs. FREE-AIR TEMPERATURE
COMPARISON OF REFERENCE RESISTOR VALUES BETWEEN AN
LX6431B AND A TL1431. Resistors used with the LX6431B are 5
times higher in value.
3.
CATHODE CURRENT vs. CATHODE VOLTAGE
8.
4.
OFF-STATE CATHODE CURRENT vs. FREE-AIR TEMPERATURE
5.
RATIO OF DELTA REFERENCE VOLTAGE TO DELTA CATHODE
VOLTAGE vs. FREE-AIR TEMPERATURE
COMPARISON OF REFERENCE RESISTOR VALUES BETWEEN AN
LX6431B AND A TL1431. When used as 0.5%, 5V shunt
regulators.
6.
EQUIVALENT INPUT NOISE VOLTAGE vs. FREQUENCY
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FIGURE #
Parameter Measurement Information
FIGURE #
9.
TEST CIRCUIT FOR VKA = VREF
10. TEST CIRCUIT FOR VKA > VREF
11. TEST CIRCUIT FOR IOFF
Typical Characteristics
FIGURE #
12. EQUIVALENT INPUT NOISE VOLTAGE OVER A 10-SECOND PERIOD
13. SMALL-SIGNAL VOLTAGE AMPLIFICATION vs. FREQUENCY
14. REFERENCE IMPEDANCE vs. FREQUENCY
15. PULSE RESPONSE
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16. DIFFERENTIAL VOLTAGE AMPLIFICATION vs. FREQUENCY
4
Copyright © 1999
Rev. 1.4a
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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CHARACTERISTIC CURVES
FIGURE 1. — REFERENCE VOLTAGE
vs. FREE-AIR TEMPERATURE
FIGURE 2. — REFERENCE CURRENT
vs. FREE-AIR TEMPERATURE
0.15
IK = 10mA
R1 = 10k
(IREF) Reference Current - (µA)
VREF = VKA
IK = 10mA
2.51
0.14
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(VREF) Reference Voltage - (V)
2.52
2.50
2.49
2.48
-50
-25
25
0
50
75
100
0.13
0.12
0.11
0.1
-50
125
(TA) Ambient Temperature - (°C)
25
50
75
100
125
FIGURE 4. — OFF-STATE CATHODE CURRENT
vs. FREE-AIR TEMPERATURE
800
0.8
(IOFF) Off-State Cathode Current - (µA)
VKA = VREF
TA = 25°C
600
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(IK) Cathode Current - (µA)
0
(TA) Ambient Temperature - (°C)
FIGURE 3. — CATHODE CURRENT vs. CATHODE VOLTAGE
400
200
0
-200
-2
-1
0
1
2
(VKA) Cathode Voltage - (V)
Copyright © 1999
Rev. 1.4a
-25
3
4
0.7
VKA = 36V
VREF = 0
0.6
0.5
0.4
0.3
0.2
0.1
0
-50
-25
0
25
50
75
100
125
(TA) Ambient Temperature - (°C)
5
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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CHARACTERISTIC CURVES
FIGURE 5. — RATIO OF DELTA REFERENCE VOLTAGE TO DELTA
CATHODE VOLTAGE vs. FREE-AIR TEMPERATURE
FIGURE 6. — EQUIVALENT INPUT NOISE VOLTAGE
vs. FREQUENCY
0
260
VKA = 3V to 36V
(VN) Noise Voltage - (nV/ Hz)
220
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∆VREF / ∆VKA - (mV/V)
IO = 10mA
TA = 25°C
240
-0.1
-0.2
-0.3
-0.4
-0.5
200
180
160
140
120
-0.6
-50
-25
0
25
50
75
100
100
10
100
1k
10k
100k
(f) Frequency - (Hz)
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(TA) Ambient Temperature - (°C)
125
6
Copyright © 1999
Rev. 1.4a
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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A P P L I C AT I O N I N F O R M AT I O N
Application Hints
VKA
5V, 0.5%
VIN
R1
1k
0.1%
R2
1k
0.1%
LX6431B
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The reference input current of the LX6431 series voltage references is much lower than other similar precision parts. This helps
to design programmable voltage references that can use much
higher value programming resistors while maintaining the same
accuracy as the other precision parts. Figure 7 below shows a 5V,
1% shunt regulator using the LX6431B and a shunt regulator using
the TL1431 (Also available from Linfinity). Figure 8 shows 0.5%
shunt regulators. Noteworthy are the values of the reference
resistors used in the two circuits. With the LX6431B it is possible
to use 25k resistors for setting the output voltage with 1%
precision as opposed to 5k programming resistors when the same
precision needs to be achieved with a TL1431.
GND
a)
VKA
5V, 0.5%
VIN
VKA
5V, 1%
VIN
R1
25k
0.1%
240
0.1%
R2
240
0.1%
TL1431
LX6431B
R2
R1
25k
0.1%
GND
b)
GND
a)
VKA
5V, 1%
VIN
R1
5k
0.1%
R2
5k
0.1%
TL1431
GND
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b)
FIGURE 7 — Comparison of reference resistor values between an
LX6431B and an TL1431, resistors used with the
LX6431B are 5 times higher in value.
Copyright © 1999
Rev. 1.4a
FIGURE 8 — Comparison of reference resistor values between an
LX6431B and a TL1431, when used as 0.5%, 5V shunt regulators.
The output voltage of the reference can be programmed by using
the formula below:
R1 

VKA ≅ 2.5 ∗ 1 +


R2 
If more accuracy is required then the effects of the input bias
current (IREF) must be taken into account. The formula below
accounts for the error this current produces.
R1 

VKA = 2.5 ∗ 1 +
 + IREF ∗ R1

R2 
Smaller values of programming resistors tend to minimize bias
current errors. In this respect the low input current characteristics
of the LX6431B helps to reduce the power dissipation on the
programming resistors by a factor of five compared to other
references like the TL1431 and TL431.
The LX6431 series of voltage references have an enhanced
circuit design that can tolerate any value of cathode to anode
capacitance.
7
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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PA R A M E T E R M E A S U R E M E N T I N F O R M A T I O N
VKA
Input
VKA
Input
IK
IK
R1
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IREF
R2
VREF
VREF
FIGURE 10 — TEST CIRCUIT FOR VKA > VREF
FIGURE 9 — TEST CIRCUIT FOR VKA = VREF
VKA
Input
IOFF
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FIGURE 11 — TEST CIRCUIT FOR IOFF
8
Copyright © 1999
Rev. 1.4a
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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R O D U C T I O N
A T A
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H E E T
TYPICAL CHARACTERISTICS
6
f = 0.1 to 10Hz
IK = 10mA
TA = 25°C
4
3
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(VN) Input Noise Voltage - (µV)
5
2
1
0
-1
-2
-3
-4
-5
-6
0
2
4
6
8
10
(t) Time - (s)
FIGURE 12. — EQUIVALENT INPUT NOISE VOLTAGE OVER A 10-SECOND PERIOD
19.1V
1k
500µF
VCC
910
2000µF
VCC
1µF
LX6431
(DUT)
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TLE2027
AV = 10V/mV
820
TLE2027
16k
16
160k
1µF
0.1µF
VEE
2.2µF
16k
33k
AV = 2V/V
1M
CRO
33k
VEE
Test Circuit for 0.1Hz to 10Hz Equivalent Input Noise Voltage
Copyright © 1999
Rev. 1.a
9
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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H E E T
TYPICAL CHARACTERISTICS
FIGURE 13. — SMALL-SIGNAL VOLTAGE AMPLIFICATION
vs. FREQUENCY
Output
IK = 10mA
TA = 25°C
60
IK
230
15k
50
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(AV) Voltage Amplification - (dB)
70
9µF
40
30
8.25k
20
10
GND
0
Test Circuit for Voltage Amplification
-10
1k
10k
100k
1M
10M
(f) Frequency - (Hz)
FIGURE 14. — REFERENCE IMPEDANCE vs. FREQUENCY
Output
IK = 1mA to 100mA
TA = 25°C
1k
IK
10
50
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(|zKA|) Reference Impedance - ( )
100
1
GND
Test Circuit for Reference Impedance
0.1
1k
10k
100k
1M
10M
(f) Frequency - (Hz)
10
Copyright © 1999
Rev. 1.4a
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
R O D U C T I O N
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TYPICAL CHARACTERISTICS
FIGURE 15. — PULSE RESPONSE
6
Output
220
4
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VIN - (V)
5
3
Pulse
Generator
f = 100kHz
2
50
(VKA)
Output Voltage - (V)
1
0
3
GND
2
1
Test Circuit for Pulse Response
0
0
1
2
3
4
5
6
(t) Time - (µs)
50
180
Phase Shift
GM/20
+35V
90
10
0
0
-10
-90
-30
-180
Phase Shift
30
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AVD - Differential Voltage Amplification - (dB)
FIGURE 16. — DIFFERENTIAL VOLTAGE AMPLIFICATION
vs. FREQUENCY
To Network
Analyzer as DUT
Input Port with
10X Probe
R3
1K
C1
R1
100K
10µF
R2
100K
C2
10µF
To Network
Analyzer as
DUT Output Port
R4
2
DUT is bias at 30mA and 5V
Test Setup for Measuring AVD vs. Frequency
-50
1k
10k
100k
1M
Frequency - (Hz)
PRODUCTION DATA - Information contained in this document is proprietary to LinFinity, and is current as of publication date. This document
may not be modified in any way without the express written consent of LinFinity. Product processing does not necessarily include testing of
all parameters. Linfinity reserves the right to change the configuration and performance of the product and to discontinue product at any time.
Copyright © 1999
Rev. 1.4a
11