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LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
T
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NFINITE
P
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N N O VAT I O N
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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 chosen 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 equipment as well as reducing the voltage programming errors due to the impedance of the divider network (See Product Highlight figure below). 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 100m. The reduced reference input bias current and minimum operating currents make these devices suitable for portable and micropower applications.
K E Y F E AT U R E S
s Unconditionally Stable For All Cathode To Anode Capacitance Values s Reduced Reference Input Current Allowing The Use Of Higher Value Divider Resistors (0.5A Max.) s Initial Voltage Reference Accuracy Of 0.4% (LX6431B) s Sink Current Capability 0.6mA to 100mA s Typical Output Dynamic Impedance Less Than 100m s Adjustable Output Voltage From 2.5V to 36V
NOTE: For current data & package dimensions, visit our web site: http://www.linfinity.com.
PRODUCT HIGHLIGHT
O U T P U T V O L TA G E E R R O R
20 18 16 14
DUE TO
I REF T Y P I C A L P R O G R A M M A B L E V O LTA G E REFERENCE CIRCUIT
VIN R1 VKA
% Error
12 10 8 6 4 2 0 2.5 3.75 5 6.25 7.5 8.75
LX6431
R2
GND
10
11.25
(VKA) Output Voltage - (V)
12.5
13.75
15
PA C K A G E O R D E R I N F O R M A T I O N TA (C)
0 to 70
Initial Tolerance
2% 1% 0.4% 2% 1% 0.4%
DM Plastic SOIC 8-pin
LX6431CDM LX6431ACDM LX6431BCDM LX6431IDM LX6431AIDM LX6431BIDM
LP Plastic TO-92 3-pin
LX6431CLP LX6431ACLP LX6431BCLP LX6431ILP LX6431AILP LX6431BILP
-40 to 85
Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. LX5212CDPT) TO-92 (LP) package also available in ammo-pack.
Copyright (c) 1999 Rev. 1.4 6/99
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE PIN OUTS
Cathode to Anode Voltage (VKA) ................................................................... -0.3V to 37V Reference Input Current (IREF) .................................................................... -50A to 10A Continuous Cathode Current (IK) ......................................................... -100mA to 150mA Operating Junction Temperature Plastic (DM & LP Packages) ................................................................................. 150C Storage Temperature Range ...................................................................... -65C to 150C Lead Temperature ..................................................................................................... 300C
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. Pin numbers refer to DIL packages only.
CATHODE N.C. ANODE N.C.
1 2 3 4
8 7 6 5
REF ANODE ANODE N.C.
DM PACKAGE (Top View)
1. CATHODE
THERMAL DATA
DM PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA LP PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA 156C/W 165C/W
2. ANODE 3. REF
LP PACKAGE (Top View)
Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow
BLOCK D IA GR A M
Cathode (K)
Ref (R)
VREF Anode (A)
2
Copyright (c) 1999 Rev. 1.4 6/99
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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ELECTRICAL CHARACTERISTICS
(Note 2)
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for LX6431C/LX6431AC/LX6431BC with 0C TA 70C, LX6431I/LX6431AI/LX6431BI with -40C TA 85C.)
Parameter
Reference Input Voltage LX6431 LX6431A LX6431B LX6431 LX6431A LX6431B Voltage Ratio, Reference to Cathode (Note 3) Reference Input Current Minimum Operating Current Off-State Cathode Current Dynamic Impedance Note 2. These parameters are guaranteed by design. Note 3. VREF VKA
Symbol
VREF
Test Conditions
IK = 10mA, VKA = VREF, TA = 25C, IK = 10mA, VKA = VREF, TA = 25C IK = 10mA, VKA = VREF, TA = 25C IK = 10mA, VKA = VREF, 0C TA 70C IK = 10mA, VKA = VREF, -40C TA 85C IK = 10mA, VKA = VREF, 0C TA 70C IK = 10mA, VKA = VREF, -40C TA 85C IK = 10mA, VKA = VREF, 0C TA 70C IK = 10mA, VKA = VREF, -40C TA 85C IK = 10mA, VKA = 2.5V to 36V, TA = 25C IK = 10mA, VKA = 2.5V to 36V, TA = Operating Range VKA = VREF, TA = 25C VKA = VREF, TA = Operating Range VKA = VREF to 36V, TA = 25C VKA = VREF to 36V, TA = Operating Range VKA = 36V, VREF = 0V, TA = 25C VKA = VREF, IK = 0.6mA to 100mA, f 1kHz, TA = 25C
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 mV mV mV mV mV mV mV mV mV mV/V mV/V A A mA mA A m
Reference Drift
IREF IMIN IOFF ZKA
0.3 0.3 0.1 0.1 0.4 0.4 0.3 30
Ratio of change in reference input voltage to the change in cathode voltage.
Copyright (c) 1999 Rev. 1.4 6/99
3
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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GRAPH / CURVE INDEX
FIGURE INDEX
Characteristic Curves
FIGURE # 1. 2. 3. 4. 5. 6. REFERENCE VOLTAGE vs. FREE-AIR TEMPERATURE REFERENCE CURRENT vs. FREE-AIR TEMPERATURE CATHODE CURRENT vs. CATHODE VOLTAGE OFF-STATE CATHODE CURRENT vs. FREE-AIR TEMPERATURE RATIO OF DELTA REFERENCE VOLTAGE TO DELTA CATHODE VOLTAGE vs. FREE-AIR TEMPERATURE EQUIVALENT INPUT NOISE VOLTAGE vs. FREQUENCY FIGURE # 9. 8. FIGURE # 7.
Application Information
COMPARISON OF REFERENCE RESISTOR VALUES BETWEEN AN LX6431B AND A TL1431. Resistors used with the LX6431B are 5 times higher in value. COMPARISON OF REFERENCE RESISTOR VALUES BETWEEN AN LX6431B AND A TL1431. When used as 0.5%, 5V shunt regulators.
Parameter Measurement Information
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 16. DIFFERENTIAL VOLTAGE AMPLIFICATION vs. FREQUENCY
4
Copyright (c) 1999 Rev. 1.4 6/99
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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D
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CHARACTERISTIC CURVES
FIGURE 1. -- REFERENCE VOLTAGE vs. FREE-AIR TEMPERATURE
2.52
FIGURE 2. -- REFERENCE CURRENT vs. FREE-AIR TEMPERATURE
0.15
(IREF) Reference Current - (A)
(VREF) Reference Voltage - (V)
VREF = VKA IK = 10mA
2.51
IK = 10mA R1 = 10kW
0.14
0.13
2.50
0.12
2.49
0.11
2.48 -50
-25
0
25
50
75
100
125
0.1 -50
-25
0
25
50
75
100
125
(TA) Ambient Temperature - (C)
(TA) Ambient Temperature - (C)
FIGURE 3. -- CATHODE CURRENT vs. CATHODE VOLTAGE
800
FIGURE 4. -- OFF-STATE CATHODE CURRENT vs. FREE-AIR TEMPERATURE
0.8
(IOFF) Off-State Cathode Current - (A)
VKA = VREF TA = 25C
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -50
VKA = 36V VREF = 0
(IK) Cathode Current - (A)
600
400
200
0
-200 -2 -1 0 1 2 3 4
-25
0
25
50
75
100
125
(VKA) Cathode Voltage - (V)
(TA) Ambient Temperature - (C)
Copyright (c) 1999 Rev. 1.4 6/99
5
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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D
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CHARACTERISTIC CURVES
FIGURE 5. -- RATIO OF DELTA REFERENCE VOLTAGE TO DELTA CATHODE VOLTAGE vs. FREE-AIR TEMPERATURE
0
FIGURE 6. -- EQUIVALENT INPUT NOISE VOLTAGE vs. FREQUENCY
260
VKA = 3V to 36V
(VN) Noise Voltage - (nV/ Hz)
-0.1
240 220 200 180 160 140 120
IO = 10mA TA = 25C
VREF / VKA - (mV/V)
-0.2
-0.3
-0.4
-0.5
-0.6 -50
-25
0
25
50
75
100
125
100 10
100
1k
10k
100k
(TA) Ambient Temperature - (C)
(f) Frequency - (Hz)
6
Copyright (c) 1999 Rev. 1.4 6/99
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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D
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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 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.
VIN R1 25k 0.1% 25k 0.1%
GND
VIN R1 1k 0.1% 1k 0.1%
VKA 5V, 0.5%
LX6431B
R2
GND
a)
VIN R1 240 0.1% 240 0.1% VKA 5V, 0.5%
VKA 5V, 1%
TL1431
R2
LX6431B
R2
GND
b)
FIGURE 8 -- Comparison of reference resistor values between an LX6431B and a TL1431, when used as 0.5%, 5V shunt regulators.
a)
VIN R1 5k 0.1% 5k 0.1% VKA 5V, 1%
The output voltage of the reference can be programmed by using the formula below:
TL1431
R2
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.
GND
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.
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.
Copyright (c) 1999 Rev. 1.4 6/99
7
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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D
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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
Input
IK
VKA
Input
IK
VKA
R1
IREF
VREF
R2
VREF
FIGURE 9 -- TEST CIRCUIT FOR VKA = VREF
FIGURE 10 -- TEST CIRCUIT FOR VKA > VREF
Input IOFF
VKA
FIGURE 11 -- TEST CIRCUIT FOR IOFF
8
Copyright (c) 1999 Rev. 1.4 6/99
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
RODUCTION
D
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TYPICAL CHARACTERISTICS
6 5
(VN) Input Noise Voltage - (V)
4 3 2 1 0 -1 -2 -3 -4 -5 -6 0 2 4 6
f = 0.1 to 10Hz IK = 10mA TA = 25C
8
10
(t) Time - (s)
FIGURE 12. -- EQUIVALENT INPUT NOISE VOLTAGE OVER A 10-SECOND PERIOD
19.1V
1kW
500F
910W 2000F LX6431 (DUT) 820W 16W
VCC VCC 1F TLE2027 AV = 10V/mV TLE2027 16kW 16kW 1F
160kW
2.2F
33kW AV = 2V/V 33kW VEE 1MW CRO
0.1F VEE
Test Circuit for 0.1Hz to 10Hz Equivalent Input Noise Voltage
Copyright (c) 1999 Rev. 1.4 6/99
9
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
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D
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TYPICAL CHARACTERISTICS
FIGURE 13. -- SMALL-SIGNAL VOLTAGE AMPLIFICATION vs. FREQUENCY
70 60 50 40 30
8.25kW 9F
(AV) Voltage Amplification - (dB)
IK = 10mA TA = 25C
15kW
Output IK 230W
20 10 0
GND
Test Circuit for Voltage Amplification
-10 1k 10k 100k 1M 10M
(f) Frequency - (Hz)
FIGURE 14. -- REFERENCE IMPEDANCE vs. FREQUENCY
100
(|zKA|) Reference Impedance - (W )
IK = 1mA to 100mA TA = 25C
Output 1kW
10
50W
IK
1
GND
Test Circuit for Reference Impedance
0.1 1k 10k 100k 1M 10M
(f) Frequency - (Hz)
10
Copyright (c) 1999 Rev. 1.4 6/99
PRODUCT DATABOOK 1996/1997
LX6431/LX6431A/LX6431B
PRECISION PROGRAMMABLE REFERENCES
P
RODUCTION
D
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TYPICAL CHARACTERISTICS
FIGURE 15. -- PULSE RESPONSE
6 5
Output 220W
VIN - (V)
4 3 2 1
Pulse Generator f = 100kHz 50W
(VKA) Output Voltage - (V)
0 3
GND
2 1 0 0 1 2 3 4 5 6
Test Circuit for Pulse Response
(t) Time - (s)
FIGURE 16. -- DIFFERENTIAL VOLTAGE AMPLIFICATION vs. FREQUENCY
AVD - Differential Voltage Amplification - (dB)
50
180
Phase Shift
30
GM/20
90
+35V R3 1K R1 100K R2 100K C2 10F To Network Analyzer as DUT Output Port
10 0 -10
0
Phase Shift
To Network Analyzer as DUT Input Port with 10X Probe
C1 10F
-90
R4 2W
-30
-180
DUT is bias at 30mA and 5V
-50 1k 10k 100k 1M
Test Setup for Measuring AVD vs. Frequency
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 (c) 1999 Rev. 1.4 6/99
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