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AT431
Preliminary Product Information 1.24V low-Voltage Adjustable Precision Shunt Regulator Features
Low-Voltage Operation: Down to 1.24V 1% Reference-Voltage Tolerance Adjustable Output Voltage, Vo=Vref to 12V Low Operational Cathode Current....50A 0.25 Typical Output Impedance SOT-23 and TO-92 Packages
Description
The AT431 is low-voltage three-terminal adjustable voltage reference with specified thermal stability over applicable commercial temperature ranges. Output voltage may be set to any value between Vref (1.24V) and 12V with two external resistors (see Figure 2). When used with an optocoupler, the AT431 is ideal voltage reference in isolated feedback circuits for 1.8V to 12 V switching-mode power supplies. This device has typical output impedance of 0.20. Active output circuitry provides a very sharp turn-on characteristic, making the AT431 excellent replacements for low-voltage zener diodes in many applications, including onboard regulation and adjustable power supplies.
Application
Linear Regulators Voltage Reference for Power Circuit
Block Diagram and Symbol
Aimtron reserves the right without notice to change this circuitry and specifications.
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 1
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator Equivalent Schematic
Pin Assignments
Ordering Information Part number AT431Z AT431UN AT431UN_GRE : Date Code
Package TO-92 SOT-23 SOT-23, Green
Marking Date Code Date Code ,Date Code with one bottom line
*For more marking information, contact our sales representative directly
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 2
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator Absolute maximum ratings (TA = 25oC)
Parameter Cathode voltage Continuous cathode current range Reference Current Operating temperature Storage temperature Package thermal impedance JA Symbol VKA IK IREF TOPR TSTG SOT-23-5 SOT-23-3 TO-92 PD Limits 12 -20~20 -0.05~3 -30~+85 -55~+150 347 156 (TJ(max)-TA)/ JA unit V mA mA o C o C o C/W
Power Dissipation
Stresses beyond those listed under " absolute maximum ratings" may cause permanent damage to the device. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Recommend operating condtion
Parameter Cathode voltage VKA Continuous cathode current range IK Operating free-air temperature range TA min Vref 0.05 0 Max 12 15 70 unit V mA o C
Electrical characteristics (unless otherwise noted)
Parameter Reference Voltage Symbol Vref (TA = 25oC) Vref (TA = full o range 0~70 C) Vref(dev) Vref / VKA Iref Iref(dev) IK(min) IK(off) | ZKA | Min. 1.228 1.221 Typ. 1.24 4 -1.5 0.15 0.05 40 0.001 0.20 Max. 1.252 1.259 20 -2.7 0.5 0.3 50 0.1 0.4 Unit V V mV Conditions VKA= Vref IK=10mA (Figure 1)
Vref deviation over full temperature range Ratio of Vref change in cathode voltage change Reference terminal current Iref deviation over full temperature range Minimum cathode current for regulation Off-state cathode current Dynamic impedance
VKA= Vref IK=10mA (Figure 1) mV/V VKA= Vref to 12V IK=10mA (Figure 2) A IK=10mA R1=10K (Figure 2) A IK=10mA R1=10K R2=open (Figure 2) A VKA= Vref (Figure 1) A VKA=12V Vref =0V (Figure 3) VKA= Vref f1KHz IK=0.1mA to 15mA
(Figure 1)
* The dynamic impedance is defined as : |ZKA| = VKA / IKA
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 3
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator Parameter Measurement Information
Figure 2. Test Circuit for VKA>Vref Figure 1. Test Circuit for VKA=Vref VO= VKA=Vref VO= VKA=Vref *(1+R1/R2)+Iref *R1
Figure 3. Test Circuit for IK(off)
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 4
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator
Figure 4.
Figure 5.
Figure 6.
Figure 7.
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 5
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator
Figure 8.
Figure 9.
Figure 10.
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 6
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator Application Circuit
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 7
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator
Above shows the AT4311 used in a 3.3V isolated flyback supply. Output voltage Vo can be as low as reference voltage Vref (1.24V1%). The output of the regulator, plus the forward voltage drop of the optocoupler LED (1.24+1.4=2.64V), determine the minimum voltage that can be regulated in an isolated in an isolated supply configuration. Regulated voltage as low as 2.7V is possible using the circuit.
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 8
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator Package Information SOT-23
SYMBOL A A1 B C D E E H L S R
MILLIMETERS MIN MAX 0.787 1.194 0.025 0.127 0.356 0.559 0.086 0.152 2.667 3.048 1.194 1.397 1.778 2.032 2.083 2.489 0.102 0.305 0.432 0.559 8 0
INCHES MIN 0.031 0.001 0.014 0.0034 0.105 0.047 0.070 0.082 0.004 0.017 0 MAX 0.047 0.005 0.022 0.006 0.120 0.055 0.080 0.098 0.012 0.022 8
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 9
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator
TO-92
SYMBOL A B C D E e e1 L
MILLIMETERS MIN MAX 3.4 3.8 0.3 0.5 4.4 4.8 4.4 4.8 0.9 1.5 1.17 1.37 2.39 2.69 12 16
INCHES MIN 0.134 0.012 0.173 0.173 0.035 0.046 0.094 0.472 MAX 0.150 0.020 0.189 0.189 0.059 0.054 0.106 0.630
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 10
AT431
Preliminary Product Information 1.24V Low-Voltage Adjustable Precision Shunt Regulator Reflow Profiles
Profile Feature
Sn-Pb Eutectic Assembly Large Body Small Body
Pb-Free Assembly Large Body Pkg. thickness 2.5mm or Pkg. volume 350mm3 Small Body Pkg. thickness 2.5mm or Pkg. volume 350mm3
Pkg. thickness 2.5mm Pkg. thickness <2.5mm 3 or Pkg. volume 350mm3 or Pkg. volume <350mm Average ramp-up rate (TL to TP) Preheat -Temperature Min(Tsmin) -Temperature Max (Tsmax) -Time (min to max)(ts) Tsmax to TL -Ramp-up Rate Time maintained above: -Temperature (TL) -Time (tL) Peak Temperature(TP) Time within 5C Temperature (tP) Ramp-down Rate Time 25C to Peak Temperature of actual Peak 225+0/-5C 10-30 seconds 183C 60-150 seconds 240+0/-5C 10-30 seconds 100C 150C 60-120 seconds 3C/second max.
3C/second max.
150C 200C 60-180 seconds 3C/second max.
217C 60-150 seconds 245+0/-5C 10-30 seconds 250+0/-5C 20-40 seconds
6C/second max. 6 minutes max.
3C/second max. 8 minutes max.
*All temperatures refer to topside of the package, measured on the package body surface.
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/8/2006 REV:1.1 Email: service@aimtron.com.tw 11

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