LIN D O C #: 1431 LX1431 PROGRAMMABLE R EFERENCE T H E I N F I N I T E P O W E R I O F P N N O VA T I O N R O D U C T I O N 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 ® 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 D S A T A H E E T K E Y F E AT U R E S 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 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. A P P L I C AT I O N S ■ ■ ■ ■ LINEAR REGULATORS ADJUSTABLE POWER SUPPLIES SWITCHING POWER SUPPLIES LX1431EB EVALUATION BOARD FOR PENTIUM APPLICATIONS AVAILABLE. CONSULT FACTORY. PRODUCT HIGHLIGHT T HE LX8584A 5V 3 AND LX1431 VIN VOUT IN 75 AND 166MH Z P54C P R O C E S S O R A P P L I C ATIONS U S I N G 3.3V C ACHE VO 7A (See Table Below) 2 3x 330µF, 6.3V Low ESR Oscon Type from Sanyo LX8584A 1kW ADJ 0.01µF 1kW 1 PLACE IN µP SOCKET CAVITY 100µF x 6 10V AVX TYPE TPS 250pF 1 2 3 220µF 10V Low ESR from Sanyo COL V+ REF LX1431 0.1µF 50V SGND 5 VO 3.50 3.38 JP1 Short Open 8 1k 0.1% 2.84kW 0.1% 21k 1% µP Load 1µF x 10 SMD JP1 FGND 6 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) DIP M Plastic 8-pin SOIC DM Plastic 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). 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 © 1997 Rev. 1.2 4/97 11861 WESTERN A VENUE , G ARDEN G ROVE , CA. 92841 1 PRODUCT DATABOOK 1996/1997 LX1431 PROGRAMMABLE REFERENCE P R O D U C T I O N A B S O L U T E M A X I M U M R AT I N G S D A T A S H E E T PACKAGE PIN OUTS (Note 1) V+, VCOLLECTOR ................................................................................................................. 36V VCOMP, RTOP, RMID, V REF ...................................................................................................... 6V GND-F to GND-S ........................................................................................................ 0.7V Operating Junction Temperature Plastic (M, DM Packages) ..................................................................................... 150°C Storage Temperature Range ...................................................................... -65°C to 150°C Lead Temperature ..................................................................................................... 300°C COLLECTOR COMP V+ RTOP COLLECTOR COMP V+ RTOP M PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ JA 8 2 7 3 6 4 5 REF RMID GND-F GND-S M PACKAGE (Top View) 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. T H E R MAL DATA 1 1 8 2 7 3 6 4 5 REF RMID GND-F GND-S 95°C/W DM PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ JA 165°C/W DM PACKAGE (Top View) Junction Temperature Calculation: TJ = TA + (PD x θJA). The θ 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 V+ 4 3 COMP 2 COLLECTOR 1 5K REF 8 RMID gm= 60µA/V 7 5K 2.5V 5 GND-SENSE 2 6 GND-FORCE Copyright © 1997 Rev. 1.2 4/97 PRODUCT DATABOOK 1996/1997 LX1431 PROGRAMMABLE R EFERENCE P R O D U C T I O N D A T A S H E E T 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 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 Copyright © 1997 Rev. 1.2 4/97 Symbol Test Conditions LX1431I LX1431C Units Min. Typ. Max. Min. Typ. Max. VKA = 5V, IK = 2mA, TA = 25°C 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 = 25°C [IREF] VKA = 5V 0.6 VKA = VREF to 36V, TA = 25°C IMIN VKA = 36V, VREF = 0V, TA = 25°C [IOFF] VKA = 36V, VREF = 0V VCOLL = 36V, V+ = 5V, VREF = 2.4V, TA = 25°C [ILEAK] V + COLL = 36V, V = 5V, VREF = 2.4V VKA = VREF, IK = 1mA to 100mA, f ≤ 1kHz, TA = 25°C [ZKA ] 80 VKA = VREF + 50mV ILIM 4950 5000 Internal Divider Used, IK = 2mA, TA = +25°C VREF 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 µA µA mA µA µA µA µA Ω mA mV 3 PRODUCT DATABOOK 1996/1997 LX1431 PROGRAMMABLE REFERENCE P R O D U C T I O N D A T A S H E E T 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. 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. 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. 4 Copyright © 1997 Rev. 1.2 4/97 PRODUCT DATABOOK 1996/1997 LX1431 PROGRAMMABLE R EFERENCE P R O D U C T I O N D A T A S H E E T GRAPH / CURVE INDEX Characteristic Curves FIGURE # 1. COLLECTOR VSAT vs. TEMPERATURE vs. CURRENT 2. COMPENSATION PIN VOLTAGE vs. TEMPERATURE vs. ICOLL 3. ILIMIT vs. TEMPERATURE WITH EXTERNAL RESISTOR 4. REFERENCE VOLTAGE and REFERENCE CURRENT vs. V+ 5. REFERENCE VOLTAGE and REFERENCE CURRENT vs. V+ 6. 2.5V REFERENCE IK vs. VKA 7. REFERENCE VOLTAGE and REFERENCE CURRENT vs. TEMPERATURE Copyright © 1997 Rev. 1.2 4/97 5 PRODUCT DATABOOK 1996/1997 LX1431 PROGRAMMABLE REFERENCE P R O D U C T I O N D S A T A H E E T CHARACTERISTIC CURVES FIGURE 1. — COLLECTOR VSAT vs. TEMPERATURE vs. CURRENT FIGURE 2. — COMPENSATION PIN VOLTAGE vs. TEMPERATURE vs. ICOLL 3 0.5 (VCOMP) Compensation Pin Voltage - (V) (VSAT) Saturation Voltage - (V) 0.6 ICOLL = 100mA 0.4 0.3 ICOLL = 50mA 0.2 ICOLL = 20mA 0.1 0 -50 2.5 2 ICOLL = 100mA 1.5 ICOLL = 10mA 1 0.5 ICOLL = 10mA -25 0 25 50 75 100 0 -50 125 (TA) Ambient Temperature - (°C) -25 25 0 50 75 100 125 (TA) Ambient Temperature - (°C) FIGURE 3. — ILIMIT vs. TEMPERATURE WITH EXTERNAL RESISTOR FIGURE 4. — REFERENCE VOLTAGE and 2.505 200 1.4 2.504 190 (VREF) Reference Voltage - (V) 1.5 ILIMIT (Normalized) 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 -50 170 IREF 2.502 160 2.501 150 140 2.50 VREF 2.499 130 120 2.498 110 2.497 100 2.496 -25 0 25 50 75 100 (TA) Ambient Temperature - (°C) 6 180 2.503 125 2.495 2.5 (IREF) Reference Current - (nA) REFERENCE CURRENT vs. V+ 90 80 2.7 2.9 3.1 3.3 3.5 V+ (V) Copyright © 1997 Rev. 1.2 4/97 PRODUCT DATABOOK 1996/1997 LX1431 PROGRAMMABLE R EFERENCE P D R O D U C T I O N A T A S H E E T CHARACTERISTIC CURVES FIGURE 5. — REFERENCE VOLTAGE and FIGURE 6. — 2.5V REFERENCE IK vs. VKA REFERENCE CURRENT vs. V+ 2.502 200 2.50 190 1000 180 900 2.499 170 2.498 160 2.497 150 2.496 140 VREF 2.495 130 800 700 IK - (µA) IREF (IREF) Reference Current - (nA) (VREF) Reference Voltage - (V) 2.501 600 500 400 2.494 120 2.493 110 2.492 100 2.491 90 100 80 0 2.490 0 15 10 5 20 25 30 35 300 200 0 40 0.5 1.0 1.5 2.0 2.5 3.0 VKA - (V) V+ (V) FIGURE 6. — REFERENCE VOLTAGE and REFERENCE CURRENT vs. TEMPERATURE 1 2.51 VREF 0.6 0.4 2.5 0.2 IREF 2.495 0 -0.2 2.49 -0.4 -0.6 2.485 (IREF) Reference Current - (nA) (VREF) Reference Voltage - (V) 0.8 2.505 -0.8 2.48 -50 -25 0 25 50 75 100 -1 125 (TA) Temperature - (°C) Pentium is a registered trademark of Intel Corporation. Copyright © 1997 Rev. 1.2 4/97 7