WO2010060069A1 - Circuit de correction de second rang et procédé de référence de tension de bande interdite - Google Patents

Circuit de correction de second rang et procédé de référence de tension de bande interdite Download PDF

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Publication number
WO2010060069A1
WO2010060069A1 PCT/US2009/065634 US2009065634W WO2010060069A1 WO 2010060069 A1 WO2010060069 A1 WO 2010060069A1 US 2009065634 W US2009065634 W US 2009065634W WO 2010060069 A1 WO2010060069 A1 WO 2010060069A1
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WO
WIPO (PCT)
Prior art keywords
voltage
circuit elements
current
resistance
bipolar transistor
Prior art date
Application number
PCT/US2009/065634
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English (en)
Inventor
Stefan Marinca
Original Assignee
Analog Devices, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Analog Devices, Inc. filed Critical Analog Devices, Inc.
Priority to JP2011537697A priority Critical patent/JP5698141B2/ja
Priority to EP09775400.6A priority patent/EP2353056B1/fr
Priority to TW098140248A priority patent/TWI485545B/zh
Publication of WO2010060069A1 publication Critical patent/WO2010060069A1/fr

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
    • G05F3/02—Regulating voltage or current
    • G05F3/08—Regulating voltage or current wherein the variable is dc
    • G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
    • G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
    • G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
    • G05F3/30—Regulators using the difference between the base-emitter voltages of two bipolar transistors operating at different current densities

Definitions

  • the present invention relates generally to voltage references and in particular to voltage references implemented using bandgap circuitry.
  • the present invention more particularly relates to a circuit and method which provides a reference voltage which compensates for typical second order voltage error.
  • a conventional bandgap voltage reference circuit is based on the addition of two voltage components having opposite and balanced temperature slopes.
  • Fig. 1 illustrates a symbolic representation of a conventional bandgap reference. It consists of a current source, 110, a resistor, 120, and a diode, 130. It will be understood that the diode represents the base-emitter junction of a bipolar transistor.
  • the voltage drop across the diode has a negative temperature coefficient, TC, of about -2.2 mV/°C and is usually denoted as a Complementary to Absolute Temperature (CTAT) voltage, since its output value decreases with increasing temperature.
  • CTAT Complementary to Absolute Temperature
  • the current source 110 in Fig. 1 is desirably a Proportional to Absolute
  • PTAT Temperature
  • the PTAT current is generated by reflecting across a resistor a voltage difference ( ⁇ V be ) of two forward-biased base-emitter junctions of bipolar transistors operating at different current densities.
  • the difference in collector current density may be established from two similar transistors, i.e. Ql and Q2 (not shown), where Ql is of unity emitter area and Q2 is n times unity emitter area.
  • the PTAT current or voltage is generated by reflecting across a resistor a voltage difference ( ⁇ V be ) of the two forward-biased base-emitter junctions of transistors Ql and Q2.
  • the resulting ⁇ V be which has a positive temperature coefficient, is provided in equation 2 below:
  • Fig. 2 illustrates the operation of the circuit of Fig. 1.
  • first order error correction Even if the two voltage components are well balanced, the corresponding reference voltage is not entirely flat over temperature as second order nonlinearity components A and B of equation 1 are not compensated. Nonlinearity components contribute to what is known as “curvature.” [07] Different methods are known to compensate for "curvature" errors. In U.S.
  • the correction current is generated from a voltage difference of two bipolar transistors, having the same emitter area, one biased with PTAT current and one with CTAT current. This correction current, proportional to a differential gain stage, is then subtracted from a Brokaw cell in order to compensate for the "curvature" error.
  • Fig. 1 shows a known bandgap voltage reference circuit.
  • Fig. 2 is a graph that illustrates how PTAT and CTAT voltages generated through the circuit of Fig. 1 may be combined to provide a reference voltage.
  • FIG. 3 shows an embodiment of the present invention.
  • Fig. 4 is a graphical representation of how the ratio of the first resistance to the second resistance in Fig. 3 may compensate for the second order error of the bandgap reference voltage.
  • Fig. 5 is a graphical representation of the simulated, calculated, and second order approximation of the bandgap reference voltage over temperature, in accordance with an embodiment of the present invention.
  • FIG. 6 shows an embodiment of the present invention wherein the output voltage has an extra CTAT component.
  • Fig. 7 is a graphical representation of the voltage reference output voltage vs. temperature in accordance with the embodiment of Fig. 6.
  • a system and method are provided for a more accurate bandgap voltage reference wherein the first and second order errors are corrected simultaneously.
  • the second order errors are corrected, advantageously providing less process variability.
  • the bandgap reference circuit of Fig. 3 is an embodiment of the present invention.
  • This circuit includes a first set of circuit elements arranged to provide a complimentary to absolute temperature (CTAT) voltage or current.
  • the first set of circuit elements may comprise transistors 370 and 375, which are supplied by current sources 330 and 340 accordingly.
  • a second set of circuit elements are arranged to provide a proportional to absolute temperature (PTAT) voltage or current.
  • the second set of circuit elements may comprise at least transistor 380, which is supplied by current source 310, and of first resistance 350.
  • transistor 382 may be included. By transistor 382 drawing base current similar to the base current drawn by transistor 375, the emitter currents supplied to transistors 370 and 380 more closely match.
  • Transistors 370 and 375 of the first set of circuit elements have emitter areas n times larger than transistors 380 and 382 of the second set of circuit elements. Thus, if the current sources 310, 320, 330, and 340 provide the same current, and the current through 350 can be neglected, transistors 380 and 382 operate at n times the current density of transistors 370 and 375.
  • a third set of circuit elements are arranged to combine the CTAT voltage or current with the PTAT voltage or current.
  • the third set of circuit elements may comprise amplifier 390 and a second resistance 385. Since there is a virtual short across the positive and negative terminals of amplifier 390, the Vbe of transistor 380 is seen at both the positive and negative terminals of amplifier 390. Accordingly, one terminal of resistance 350 is at Vbe from transistor 380 while the transistor stack of 370 and 375 provides 2Vbe at the opposite terminal of resistance 350. Thus, amplifier 390 combines the CTAT component of transistors 370 and 375 and the ⁇ Vbe component across resistance 350 to create the bandgap reference voltage at output 395.
  • the ratio of second resistance 385 to first resistance 350 controls the output gain of amplifier 390.
  • amplifier 390 can provide the gain to balance the two voltage components of Vbe and ⁇ V be .
  • the specific ratio of the second resistance 385 to the first resistance 350 provides a gain that may be used in balancing the two voltage components of Vbe and ⁇ V be . This balancing can accommodate the first order errors.
  • the calculations below provide further insight:
  • V be (Q n ) V be (Q x ) -W be (Eq.5)
  • Ql is transistor 380
  • Q n is a transistor having n times emitter width (i.e. transistor 370 or 375).
  • the voltage across resistance 350 is:
  • K 1 2V ⁇ (Q 1 ) ⁇ 2AV be - V 1x (Q 1 ) (Eq.6)
  • V r ⁇ V be (Q ⁇ ) - 2W be (EqJ)
  • the V be (Qi) component may be of the order of 60OmV to 70OmV.
  • ⁇ V be is only about 10OmV. Accordingly, a gain factor is required to balance the two voltage components.
  • the ratio of second resistance 385 to first resistance 350 controls the output gain of amplifier 390. Equation 8 below provides the reference voltage at output 395 taking the gain factor into consideration.
  • V ref is the voltage at output 395
  • Qi is transistor 380
  • ri is resistance 350
  • r 2 is resistance 385.
  • current sources 310, 320, 330, and 340 are assumed to be generated from the emitter voltage difference of transistors 382 and 380, on the one hand, and 375 and 370, on the other, reflected across a resistance r 0 (not shown). These bias currents are assumed to be the same, as provided in equation 9 below:
  • Ii is the current through source 310
  • 1 2 is the current through source 320
  • 1 3 is the current through source 330.
  • the bias current 340 which is denoted as I 4 in subsequent equations, supplies the currents to the emitter of transistor 375 and resistance 350.
  • the bias current 340 may have the same temperature dependency as bias currents 310, 320, and 330 such that at room temperature (T 0 ) all bipolar transistors (370, 375, 380, and 382) are operating at substantially the same emitter currents.
  • T 0 room temperature
  • the base current effect on bipolar transistor stack i.e. transistors 370 and 375
  • the emitter current of transistor 375 may differ from those of transistors 310, 320, and 330 as the current through resistance 350 is a shifted CTAT, as provided by equation 10 below:
  • Qi is transistor 380
  • Q 3 is transistor 370
  • Q 4 is transistor 375.
  • I 4 the current through the emitter of Q 4 plus the current through rl, is PTAT current
  • I(ri), the current through resistance ri is shifted CTAT current
  • the current through the emitter of Q4 is shifted PTAT.
  • Fig. 4 illustrates the emitter current of Q4 (410) in relation to the emitter current of Qi, Q 2 , Q 3 , and Q 4 (420). This shifted PTAT response is provided in equation 14 below:
  • V be (Q r ) V G ⁇ --) + V b ⁇ O (T o y- -( ⁇ - ⁇ y — * ⁇ n(-) (Eq. ⁇ 5) T 0 T 0 q T 0
  • V be (Q 2 ) V GO ( ⁇ -—) + V be2O (T o y — - ( ⁇ - ⁇ y * ln(— ) (Eq.l ⁇ )
  • V be (Q,) V GO ( ⁇ --) + V be3O (T o y-- (a- ⁇ y — Hn(-) (EqAl)
  • V b AQ ⁇ ) V GO ( ⁇ --) + V be ⁇ O (T o y-- ⁇ * — nn(-) + — nn(- ⁇ -) (Eq. ⁇ %) T 0 T 0 q T 0 q T 0 - T 1
  • V be io, V be 2o, V be 3o, and V be 4o are the corresponding base-emitter voltages at reference or room temperature, T 0 , and ⁇ is the saturation current temperature exponent.
  • V ref - ⁇ r * [V be (Q i ) + V be (Q ⁇ ) ⁇ + ( ⁇ +- r ⁇ -y V be (Q ⁇ ) (Eq. ⁇ 9)
  • V ref can be calculated:
  • Fig. 5 provides three reference voltage plots.
  • Plot 510 represents the simulated voltage reference with respect to the embodiment illustrated in Fig. 1.
  • Plot 520 represents an exact calculation based on equation 20 above.
  • Plot 530 represents the second order approximation according to equations 21 to 24.
  • the simulated response 510 is within 1% of the exact calculation 520 and the second order approximation 530.
  • all three diagrams show that the curvature due to the T(logT) error is compensated.
  • the total deviation of simulated voltage reference is about 82uV, which corresponds to a thermal coefficient (TC) of 2.3ppm/°C. Accordingly, this exemplary embodiment is validated as well as the different approaches in calculating and simulating the output reference voltage.
  • Fig. 6 shows an embodiment of the present invention with a corrected higher reference voltage.
  • This circuit includes a first set of circuit elements arranged to provide a CTAT voltage or current.
  • the first set of circuit elements may comprise transistors 670 and 675, which are supplied by current sources 630 and 640 accordingly.
  • resistance 655 includes the purpose of advantageously increasing the output voltage by injecting an extra CTAT component into feedback resistance 685.
  • a second set of circuit elements are arranged to provide a PTAT voltage or current.
  • they may comprise at least transistor 680 which is supplied by current source 610, and a first resistance 650.
  • Transistors 670 and 675 of the first set of circuit elements have emitter areas n times that of transistor 680 of the second set of circuit elements.
  • transistor 680 operates at a current density n times the current density of transistors 670 and 675.
  • a third set of circuit elements are arranged to combine the CTAT voltage or current with the PTAT voltage or current.
  • the third set of circuit elements may comprise amplifier 690 and a second resistance 685.
  • the principles provided in the discussion of Fig. 3 largely apply to this circuit as well. However, due to resistance 655, an extra CTAT component is injected into the feedback resistance 685, thereby increasing the output voltage 695.
  • Fig. 7 illustrates a reference voltage vs. temperature of a circuit according to the principles embodied in the circuit of Fig. 6.
  • Graph 710 illustrates the curvature error is only marginally overcorrected and are mainly attributable to simulation tolerances.
  • the resulting temperature coefficient of the reference voltage of Fig. 7 is about 4ppm/°C for the temperature ranging from -40 0 C to 125 0 C.

Abstract

L'invention concerne un système et procédé de référence de tension de bande interdite plus précis dans lequel les erreurs de premier rang et de second rang sont corrigées simultanément. Les composants inclus dans la correction de l'erreur de premier rang permettent de corriger les erreurs de second rang, réduisant avantageusement la variabilité du processus.
PCT/US2009/065634 2008-11-24 2009-11-24 Circuit de correction de second rang et procédé de référence de tension de bande interdite WO2010060069A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP2011537697A JP5698141B2 (ja) 2008-11-24 2009-11-24 バンドギャップ基準電圧の二次補正回路および方法
EP09775400.6A EP2353056B1 (fr) 2008-11-24 2009-11-24 Circuit de correction de second rang et procédé de référence de tension de bande interdite
TW098140248A TWI485545B (zh) 2009-11-24 2009-11-25 用於帶隙電壓參考之二階修正電路及方法

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US12/277,042 US8710912B2 (en) 2008-11-24 2008-11-24 Second order correction circuit and method for bandgap voltage reference
US12/277,042 2008-11-24

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WO2010060069A1 true WO2010060069A1 (fr) 2010-05-27

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US7902912B2 (en) * 2008-03-25 2011-03-08 Analog Devices, Inc. Bias current generator
US8717090B2 (en) * 2012-07-24 2014-05-06 Analog Devices, Inc. Precision CMOS voltage reference
US9411355B2 (en) * 2014-07-17 2016-08-09 Infineon Technologies Austria Ag Configurable slope temperature sensor
US10691156B2 (en) * 2017-08-31 2020-06-23 Texas Instruments Incorporated Complementary to absolute temperature (CTAT) voltage generator
US10409312B1 (en) * 2018-07-19 2019-09-10 Analog Devices Global Unlimited Company Low power duty-cycled reference

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US5325045A (en) * 1993-02-17 1994-06-28 Exar Corporation Low voltage CMOS bandgap with new trimming and curvature correction methods
EP1359490A2 (fr) * 2002-04-29 2003-11-05 AMI Semiconductor, Inc. Référence de tension du type Bandgap utilisant des paires différentielles pour compensation de température
WO2004077192A1 (fr) * 2003-02-27 2004-09-10 Analog Devices, Inc. Circuit de reference de tension a barriere de potentiel et procede de production d'une reference de tension corrigee en courbure de temperature
US20080074172A1 (en) * 2006-09-25 2008-03-27 Analog Devices, Inc. Bandgap voltage reference and method for providing same

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US7173407B2 (en) * 2004-06-30 2007-02-06 Analog Devices, Inc. Proportional to absolute temperature voltage circuit
US7193454B1 (en) * 2004-07-08 2007-03-20 Analog Devices, Inc. Method and a circuit for producing a PTAT voltage, and a method and a circuit for producing a bandgap voltage reference
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EP1359490A2 (fr) * 2002-04-29 2003-11-05 AMI Semiconductor, Inc. Référence de tension du type Bandgap utilisant des paires différentielles pour compensation de température
WO2004077192A1 (fr) * 2003-02-27 2004-09-10 Analog Devices, Inc. Circuit de reference de tension a barriere de potentiel et procede de production d'une reference de tension corrigee en courbure de temperature
US20080074172A1 (en) * 2006-09-25 2008-03-27 Analog Devices, Inc. Bandgap voltage reference and method for providing same

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US20100127763A1 (en) 2010-05-27
EP2353056A1 (fr) 2011-08-10
JP5698141B2 (ja) 2015-04-08
EP2353056B1 (fr) 2019-05-08
US8710912B2 (en) 2014-04-29
JP2012510112A (ja) 2012-04-26

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