LT431 ADJUSTABLE PRECISION SHUNT REGULATOR FEATURES * Precision reference voltage : LT431O : 2.495V0.4% LT431N : 2.495V1.0% * Adjustable output voltage is VREF to 36V * Sink current capability is 200mA * Low dynamic output impedance is 0.2 (typ.) * Minimum Cathode current for regulation is 0.2mA (typ.) * Plastic material has UL flammability classification 94V-0 GENERAL DESCRIPTION The LT431 is a low voltage three terminal adjustable shunt regulator with a guaranteed thermal stability over applicable temperature ranges. The output voltage can be set to any value between 2.495V (VREF) to 36V with two external resistors (see application circuit). The high precise Reference voltage tolerance is 0.4% and 1.0% by LT431. This device has a typical output impedance of 0.2. Active output circuitry provides a very sharp turn on characteristic, making this device excel lent replacement for Zener diodes in many applications. Block Diagram & Symbol Absolute Maximum Ratings (at TA=25C) Characteristics Symbol Rating Unit Cathode Voltage VKA 40 V Continuous Cathode Current IKA 250 mA Reference Input Current IREF 10 mA Junction Temperature TJ 160 C Storage Temperature TSTG -40~150 C 0.68 W 0.25 W Power Dissipation (Note1) TO-92 SOT-23 PD Note1 : Ratings apply to ambient temperature at 25C 1 Rev 4.3 LT431 Recommended Operating Conditions Characteristics Symbol Min Max Unit Cathode Voltage VKA VREF 36 V Cathode Current IKA 0.5 200 mA Operating Temperature (Operating free-air temperature) TA -20 85 C Electrical Characteristics (TA=25C, unless otherwise specified) Characteristics Symbol Conditions 0.4 % Reference Voltage VREF Reference Input Current Deviation of Reference Input Current over Temperature Max 2.485 2.495 2.505 Unit V 2.470 2.520 VKA = VREF, IKA = 10mA, TA = -20~85C (Fig.1) 6.0 20 mV IREF R1 = 10K,R2 = IKA= 10mA (Fig.2) 1.5 3.5 uA IREF(DEV) R1 = 10K,R2 = IKA = 10mA TA = -20~85C (Fig.2) 0.4 1.2 uA -1.2 -2.0 VREF(DEV) VKA = 10V ~VREF Ratio of the Change in Reference VKA = 10V ~VREF - -1.2 -2.0 Voltage to the Change in Cathode Voltage VREF VKA Minimum Cathode Current for Regulation IKA(min) Off-state Cathode Current IKA(OFF) Dynamic Output Impedance Typ VKA = VREF, I KA = 10mA (Fig.1) 1.0 % Deviation of Reference Input Voltage over full temperature range Min IKA = 10mA (Fig.2) mV/V VKA= 36V ~10V ZKA -1 -2.0 VKA = VREF (Fig.1) 0.2 0.5 mA VKA = 36V, VREF = 0V (Fig.3) 0.1 1 uA V KA = VREF Frequency 1KHz (Fig.1) 0.2 0.5 2 Rev 4.3 LT431 Application Circuit Fig1: VKA=VREF Fig2: VKA>VREF Fig3: Off state current 3 Rev 4.3 LT431 Typical Characteristics 4 Rev 4.3 LT431 Typical Characteristics (Continued) (1) Small Signal Voltage Amplification Vs Frequency (2) Reference Impedance VS Frequency 5 Rev 4.3 LT431 Typical Characteristics (Continued) (3) Pulse Response (4) Stability boundary conditions 6 Rev 4.3 LT431 Ordering Information LT431 X X X X Reference Voltage Package Tolerance O : +/- 0.4% N : +/- 1.0% H : TO-92 CA : SOT-23 CR : SOT-23R Product Number LT431OHPA LT431NHPA LT431OCAPA LT431NCAPA LT431OCRPA LT431NCRPA Lead Free Packing P : Green A : Tape & Reel Output Voltage Tolerance Package Lead Free Packing 0.4 % 1.0 % 0.4 % 1.0 % 0.4 % 1.0 % TO-92 TO-92 SOT-23 SOT-23 SOT-23R SOT-23R Green Green Green Green Green Green Taping & Reel Taping & Reel Taping & Reel Taping & Reel Taping & Reel Taping & Reel Pin Assignment (1) TO-92 (2) SOT-23 (Top View) (Top View) CATHODE ANODE (3) SOT-23R (Top View) 2 CATHODE 2 REF ANODE ANODE 3 REF 1 CATHODE 3 1 REF Marking Information (1) TO-92 LT YM 431XXX (2) SOT-23 & SOT-23R 1) YM = Date Code, Y: Year, M: Month 1) YM = Date Code, Y: Year, M: Month XXX YM 2) 431xxx = Product Number LT431OHPA: 431OHP LT431NHPA: 431NHP 7 2) xxx = Product Number LT431OCAPA: OCA LT431NCAPA: NCA LT431OCRPA: OCR LT431NCRPA: NCR Rev 4.3 LT431 Mechanical Information (1) Package type: TO-92 Unit: mm DIM. MIN. MAX. A 4.30 4.70 B 4.30 4.70 D 0.38 0.55 E 1.10 1.40 F 3.30 3.70 G 2.44 2.64 H 0.36 0.51 I 1.27 TYP. J 13.00 14.00 K 3.50 4.50 L 2.20 2.80 8 Rev 4.3 LT431 Mechanical Information (Continued) (1) Package type: SOT-23 & SOT-23R Unit: mm DIM. MIN. MAX. A 0.89 1.15 B 0.3. 0.51 C 0.08 0.18 D 2.75 3.04 E 1.2 1.4 F 0.95 TYP. G 1.70 2.10 H 2.10 2.75 I 0.0 0.1 L L1 0.55 Typ. 0.30 9 0.50 Rev 4.3 LT431 Important Notice and Disclaimer LSC reserves the right to make changes to this document and its products and specifications at any time without notice. Customers should obtain and confirm the latest product information and specifications before final design, purchase or use. LSC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does LSC assume any liability for application assistance or customer product design. LSC does not warrant or accept any liability with products which are purchased or used for any unintended or unauthorized application. No license is granted by implication or otherwise under any intellectual property rights of LSC. LSC products are not authorized for use as critical components in life support devices or systems without express written approval of LSC. 10 Rev 4.3