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LIN D O C #: 1431
LX1431
PROGRAMMABLE R EFERENCE
T
HE
I
NFINITE
P
OWER
OF
I
N N O VAT I O N
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
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 (R) 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 exter nal 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 external 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.
K E Y F E AT U R E S
p GUARANTEED 0.4% INITIAL VOLTAGE TOLERANCE p 0.1 TYPICAL DYNAMIC OUTPUT IMPEDANCE p FAST TURN-ON p SINK CURRENT CAPABILITY, 1mA TO 100mA p LOW REFERENCE PIN CURRENT
A P P L I C AT I O N S
s s s s LINEAR REGULATORS ADJUSTABLE POWER SUPPLIES SWITCHING POWER SUPPLIES LX1431EB EVALUATION BOARD FOR PENTIUM APPLICATIONS AVAILABLE. CONSULT FACTORY.
PRODUCT HIGHLIGHT
THE LX8584A
5V 3
AND
LX1431
VOUT 2
IN
75
AND
166MHZ P54C PROCESSOR APPLICATIONS USING 3.3V C ACHE
VO 7A (See Table Below) PLACE IN P SOCKET CAVITY
VIN
LX8584A
1kW ADJ 1 250pF 2 220F 10V Low ESR from Sanyo 0.1F 50V 3 V+ 1 COL REF 8 2.84kW 0.1% 1kW 0.01F
3x 330F, 6.3V Low ESR Oscon Type from Sanyo 100F x 6 10V AVX TYPE TPS
1k 0.1%
P Load
LX1431
SGND 5 FGND 6
21k 1% JP1
1F x 10 SMD
VO 3.50 3.38
JP1 Short Open
TYPICAL APPLICATION 120/166MHz, VRE, 3.3V Cache 75/90/100/133MHz, STND, 3.3V Cache
Thick traces represent high current traces which must be low resistance / low inductance traces in order to achieve good transient response.
PA C K A G E O R D E R I N F O R M AT I O N TA (C) 0 to 70 -40 to 85
M Plastic DIP 8-pin
LX1431CM LX1431IM
DM Plastic SOIC 8-pin
LX1431CDM LX1431IDM
Note: All surface mount packages are available in Tape & Reel. Append the letter "T" to part number (i.e. LX1431CDMT).
F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
Copyright (c) 1997 Rev. 1.2 4/97
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841
1
PRODUCT DATABOOK 1996/1997
LX1431
PROGRAMMABLE REFERENCE
P
RODUCTION
D
ATA
S
HEET
A B S O L U T E M A X I M U M R AT I N G S
(Note 1)
PACKAGE PIN OUTS
V+, VCOLLECTOR ................................................................................................................. 36V VCOMP, RTOP, RMID, V REF ...................................................................................................... 6V GND-F to GND-S ........................................................................................................ 0.7V Operating Junction Temperature Plastic (M, DM 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.
COLLECTOR COMP V+ RTOP
1 2 3 4
8 7 6 5
REF RMID GND-F GND-S
M PACKAGE (Top View)
T H E R MAL DATA
M PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA DM PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA 165C/W 95C/W
COLLECTOR COMP V+ RTOP
1 2 3 4
8 7 6 5
REF RMID GND-F GND-S
DM 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.
B LO C K DIAG R A M
RTOP 4 5K REF 8 7
V+ 3
COMP 2
COLLECTOR 1
gm= 60A/V
RMID
5K
2.5V
5 GND-SENSE
6 GND-FORCE
2
Copyright (c) 1997 Rev. 1.2 4/97
PRODUCT DATABOOK 1996/1997
LX1431
PROGRAMMABLE R EFERENCE
P
RODUCTION
D
ATA
S
HEET
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for LX1431C with 0C TA 70C, LX1431I with -40C TA 85C.)
Parameter
Reference Voltage Reference Drift Voltage Ratio, Reference to Cathode (Open Loop Gain) Reference Input Current Minimum Operating Current Off-State Cathode Current Off-State Collector Leakage Current Dynamic Impedance Collector Current Limit 5V Reference Output
Symbol
VREF
Test Conditions
LX1431I LX1431C Units Min. Typ. Max. Min. Typ. Max.
2510 2490 2500 2510 mV 2535 2480 2520 mV 30 ppm/C 1.0 0.2 1.0 mV/V 1 0.2 1 1.5 1.2 1 0.6 1 1 1 15 2 1 1 5 2 0.1 0.1 360 100 360 5050 4950 5000 5050 A A mA A A A A mA mV
VKA = 5V, IK = 2mA, TA = 25C 2490 2500 VKA = 5V, IK = 2mA 2465 VREF/T VKA = 5V, IK = 2mA 50 0.2 V REF IK = 2mA, VKA = 3V to 36V VKA 0.2 VKA = 5V, TA = 25C [IREF] VKA = 5V 0.6 VKA = VREF to 36V, TA = 25C IMIN VKA = 36V, VREF = 0V, TA = 25C [IOFF] VKA = 36V, VREF = 0V VCOLL = 36V, V+ = 5V, VREF = 2.4V, TA = 25C [ILEAK] V + COLL = 36V, V = 5V, VREF = 2.4V VKA = VREF, IK = 1mA to 100mA, f 1kHz, TA = 25C [ZKA ] 80 VKA = VREF + 50mV ILIM 4950 5000 Internal Divider Used, IK = 2mA, TA = +25C
Copyright (c) 1997 Rev. 1.2 4/97
3
PRODUCT DATABOOK 1996/1997
LX1431
PROGRAMMABLE REFERENCE
P
RODUCTION
D
ATA
S
HEET
A P P L I C AT I O N I N F O R M AT I O N 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 VREF (2.5V). The quiescent current is typically 0.6mA. Pin 4 RTOP: Top of the on-chip 5k-5k resistive divider that 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 RMID: Middle of the on-chip resistive divider string between RTOP and GND-S. The pin is tied to REF for selfcontained 5V operation. It may be left open if unused. Pin 8 REF: Control pin of the shunt regulator with a 2.5V threshold. COMP, RTOP, RMID, and REF have static discharge protection circuits that must not be activated on a continuous basis. 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.
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Copyright (c) 1997 Rev. 1.2 4/97
PRODUCT DATABOOK 1996/1997
LX1431
PROGRAMMABLE R EFERENCE
P
RODUCTION
D
ATA
S
HEET
GRAPH / CURVE INDEX
Characteristic Curves
FIGURE # 1. 2. 3. 4. 5. 6. 7. COLLECTOR VSAT vs. TEMPERATURE vs. CURRENT COMPENSATION PIN VOLTAGE vs. TEMPERATURE vs. ICOLL ILIMIT vs. TEMPERATURE WITH EXTERNAL RESISTOR REFERENCE VOLTAGE and REFERENCE CURRENT vs. V+ REFERENCE VOLTAGE and REFERENCE CURRENT vs. V+ 2.5V REFERENCE IK vs. VKA REFERENCE VOLTAGE and REFERENCE CURRENT vs. TEMPERATURE
Copyright (c) 1997 Rev. 1.2 4/97
5
PRODUCT DATABOOK 1996/1997
LX1431
PROGRAMMABLE REFERENCE
P
RODUCTION
D
ATA
S
HEET
CHARACTERISTIC CURVES
FIGURE 1. -- COLLECTOR VSAT vs. TEMPERATURE vs. CURRENT
0.6
FIGURE 2. -- COMPENSATION PIN VOLTAGE
vs. TEMPERATURE vs. ICOLL
3
(VSAT) Saturation Voltage - (V)
0.5
(VCOMP) Compensation Pin Voltage - (V)
ICOLL = 100mA
2.5
0.4
2 ICOLL = 100mA 1.5 ICOLL = 10mA 1
0.3 ICOLL = 50mA
0.2
0.1
ICOLL = 20mA
0.5
0 -50
ICOLL = 10mA -25 0 25 50 75 100 125
0 -50
-25
0
25
50
75
100
125
(TA) Ambient Temperature - (C)
(TA) Ambient Temperature - (C)
FIGURE 3. -- ILIMIT vs. TEMPERATURE WITH EXTERNAL RESISTOR
1.5 1.4 1.3
FIGURE 4. -- REFERENCE VOLTAGE and
REFERENCE CURRENT vs. V+
2.505 2.504 200 190
2.503 2.502 2.501 2.50 2.499 2.498 2.497 2.496 2.495 2.5
ILIMIT (Normalized)
1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 -50
IREF
170 160 150 140
VREF
130 120 110 100 90 80
-25
0
25
50
75
100
125
2.7
2.9
3.1
3.3
3.5
(TA) Ambient Temperature - (C)
V+ (V)
6
Copyright (c) 1997 Rev. 1.2 4/97
(IREF) Reference Current - (nA)
(VREF) Reference Voltage - (V)
180
PRODUCT DATABOOK 1996/1997
LX1431
PROGRAMMABLE R EFERENCE
P
RODUCTION
D
ATA
S
HEET
CHARACTERISTIC CURVES
FIGURE 5. -- REFERENCE VOLTAGE and
REFERENCE CURRENT vs. V+
2.502 2.501 200
FIGURE 6. -- 2.5V REFERENCE IK vs. VKA
2.499 2.498 2.497 2.496 2.495 2.494 2.493 2.492 2.491 2.490 0 5 10 15 20 25 30 35 40
170 160 150 140
(IREF) Reference Current - (nA)
(VREF) Reference Voltage - (V)
2.50
IREF
190 180
1000 900 800 700
IK - (A)
600 500 400 300 200 100 0 0 0.5 1.0 1.5 2.0 2.5 3.0
VREF
130 120 110 100 90 80
V+ (V)
VKA - (V)
FIGURE 6. -- REFERENCE VOLTAGE and
REFERENCE CURRENT vs. TEMPERATURE
2.51 1 0.8
VREF
0.6 0.4
2.5
IREF
2.495
0.2 0 -0.2
2.49
-0.4 -0.6 -0.8
2.485
2.48 -50
-25
0
25
50
75
100
-1 125
(TA) Temperature - (C)
(IREF) Reference Current - (nA)
(VREF) Reference Voltage - (V)
2.505
Pentium is a registered trademark of Intel Corporation. Copyright (c) 1997 Rev. 1.2 4/97
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