JP2754779B2 - LSI built-in reference current source circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI built-in reference current power supply circuit.

[Conventional technology]

With the recent high precision of characteristics required for LSIs, there has been an increasing problem of product variations in temperature characteristics and characteristic values of a reference current source circuit built in the LSI.

Conventionally, when a reference current source circuit is built in an LSI, a method is used in which a relatively stable reference voltage source such as a Zener diode or a band gap reference is created, and this is divided by a resistor to use a reference current. I have.

When this resistor is incorporated in an LSI, the stability of the reference current is not good due to the variation in absolute accuracy and the temperature coefficient.

In order to obtain high-precision constant current, INTERNATIONAL CONFERENCE ON CONSUMER ELECTRO
NICS) and Digest of Technical Papers (1989), p. 151, use a highly accurate and stable external reference resistor.

For example, the absolute accuracy of the reference resistor is ± 20% and the temperature coefficient is 2000
PPM / ℃, operating temperature range (-25 to +25 to +125) ℃
Then, the error of the resistance value is -30 to + 40% at the maximum.
Further, when a capacitor charging circuit is configured using a constant current source having such a large error, the time constant is also -30 to +
It is about 40%.

[Problems to be solved by the invention]

The above-described conventional LSI built-in reference current source circuit has a drawback in that it requires a highly stable and highly accurate external reference resistor to obtain good temperature characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide an LSI built-in reference voltage source circuit which has good stability without requiring an external high-performance reference resistor.

[Means for solving the problem]

An LSI built-in reference current source circuit according to the present invention includes a temperature characteristic compensation voltage trimming circuit that trims a divided voltage value of an internal constant voltage and outputs a reference voltage, and an emitter (source) that inputs the divided voltage value to a common control terminal. A plurality of transistors each having a current setting resistor, a plurality of current switches each having one end connected to the collector (drain) of the transistor and the other end supplying an output current to a common output terminal, and outputting a trimming setting signal to output the reference voltage. And a trimming setting circuit having a one-time write memory means for setting the trimming of the current switch.

In addition, the LSI built-in reference current source circuit of the present invention includes a temperature characteristic compensation voltage trimming circuit having a bandgap type reference voltage source that outputs a predetermined reference voltage, and the reference voltage input to one end and the other end to the other end. An operational amplifier that feeds back a feedback voltage and an output signal of the operational amplifier are input to a control terminal, and an emitter (source) is connected to a trimable current setting resistor to generate the feedback voltage, and a collector (drain) is output to an output terminal. A constant current trimming circuit for supplying a constant current; and a trimming setting circuit having a one-time write memory unit for outputting a trimming setting signal to perform trimming of the reference voltage and trimming of the current switch. .

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

 FIG. 1 is a circuit example of the first embodiment of the present invention.

Reference current circuit includes a temperature compensation voltage trimming circuit 1 having a V _B select switch S _W for selecting the reference voltage V _B which is proportional to the constant voltage V _Z, respectively common base B inputs the reference voltage V _B A constant current trimming circuit 2 having transistors Q _{1 to} Q ₃ whose emitters are connected to current setting resistors R _{1 to} R ₃ and whose respective collectors are connected to a common output terminal T ₀ via current switches S _{1 to} S _3. When driving a drive signal d to the V _B select switch S _W by EPROM5 and its output signal set trimming information in LSI manufacturing process by the write circuit 6, also the current switch S ₁ to S ₃ signal d ₁ to d ₃ Register 4 that supplies
And a trimming setting circuit 3 having

Where the upper and lower voltage divider high resistances R _U and R _{D have an} intermediate low resistance r
₁ and r ₂ are set to a value of about 10%.

Therefore, the upper and lower divided voltages V _BU and V _BD are set to + 10% and −10%, respectively, with respect to the center divided voltage V _BC .

The current setting resistor R ₂ and R ₃ each emitter is set to resistor R ₁ to 10-fold and 5-fold, respectively.

Thus the collector current I ₂ and I ₃ of the transistor Q _2, Q ₃ becomes each 0.1I ₁ and 0.2i ₁ to I ₁ to the current.

 Next, the operation of the circuit will be described.

Temperature compensation voltage trimming circuit 1, a constant current I ₁ is applied to the constant voltage diode ZD, the constant voltage V _Z dividing resistors R _U, r
_1, r _2, R _D at V _BU respectively, V _BC, pressurized to min V _BD, V _B select switch S _W with NPN transistors Q selects one of them
It supplies the common base B of ₁ to Q _3.

A resistance voltage (V _B −V _BE ) obtained by subtracting the base-emitter voltage V _BE from the reference voltage V _B is applied to each of the emitter resistors R _{1 to} R _3, and the currents I _{1 to} I ₃ divided by the respective resistance values are applied. Is a transistor
Q ₁ is output from the collectors of to Q _3, a current switch S ₁ to S ₃
The output constant current I ₀ selectively synthesized by allowing overlap using
There is obtained from the output terminal T _0.

Here, when the temperature characteristic of the voltage V _Z of the Zener diode ZD of the temperature compensation voltage trimming circuit 1 is 0, the divided reference voltage V _B has no temperature characteristics, V _B select switch S reference voltage V _B according to the position selection of _W is only changed to _{V BU, V BC, V BD} .

The collector current I ₁ of the example, a transistor Q ₁ constant current trimming circuit 2 is generally represented by equation (1).

I ₁ = (V _B −V _BE ) / R ₁ (1) When this is logarithmically differentiated with the temperature T, the following equation (2) is obtained.

here Is (+ 2000ppm) / ° C, when (V _B −V _BE ) is 1V Is (+2000 ppm) / ° C, so from equation (2) Becomes 0.

Also, by changing the value of V _B from the equation (2) Conversely, it seen is given some positive or negative temperature characteristic on the output current I _1.

Can be trimmed variations in first order temperature characteristic of the resistor and base-emitter voltage V _BE by slightly changing the reference voltage V _B reversed.

Above mentioned manner, V _B select switch S _W advance and the temperature characteristics of the output constant current I ₀ at the center voltage V _BC is designed to be zero, the output current I obtained by actual measurement in the manufacturing process the temperature characteristic of _0, for example, + EPR trimming setting circuit 3 to select the larger voltage V _BU of the case of the temperature coefficient of
The trimming information is written into OM5 and the trimming signal d is output from the register 4.

As described above, a constant current source having no temperature characteristic was obtained as the output current I ₀ for the transistor current I ₁ , but the constant current value of this current source was further set by the reference voltage V _B and the current setting resistor R. Trimming with a variation ΔR of ₁ is required.

Therefore, when the transistor currents I ₂ and I ₃ are obtained in the transistors Q ₂ and Q ₃ using R ₂ and R ₃ having the same temperature characteristics as R ₁ , those currents also have the same temperature characteristics as the collector current I _1. I have.

Also, since the manufacturing processes are the same, the transistor currents I ₁ , I ₂ and I ₂
The relative ratio of ₃ is relatively easy to take accurately.

Here, when the transistor currents I _{1 to} I ₃ are set as described above, I ₁ , 1.1I ₁ , 1.2I ₁ , and 1.3I ₁ are output setting currents I ₀ in combination with the current switches S _{1 to} S ₃ . since obtained previously by the I ₁ should make slightly smaller than the predetermined output current value I _0, ± by selecting any of the above 0.05I ₀
Can be trimmed.

Combination of setting of the current switch S ₁ to S _3, in order to trim the setting of the reference current source circuit during the manufacturing process, first,
V _B select switch S _W central divided voltage V _BC and the current switch S ₁ only if Pick in advance but a first temperature coefficient of the output constant current I _0, then to compensate cancels the temperature coefficient as trimming signal d is put out to drive the V _B select switch S _W, also write set of one-time EPROM5 to put out a trimming signal d ₁ to d ₃ of the combination of current switches for trimming a constant current value .

 In this case, the memory may be a fuse ROM.

Further, the number of resistors, transistors and switches may be increased in order to perform fine trimming.

 The transistor may be a MOS type.

 FIG. 2 is a circuit diagram of a second embodiment of the present invention.

The constant-voltage circuit uses a circuit of band gap reference type, the transistor Q ₁₂ diode Q ₁₁
And 10-fold joining the size of the diode current I ₁₁ and the transistor current I ₁₂ is the (3), is obtained to the equation (4).

When _{I 11 = I s · exp (} qV D / kT) ...... (3) I 12 = 10I s exp (qV BE12 / kT) ...... (4) will now be equal to I ₁₁ and I _12, the diode voltage V _D And the transistor voltage V _BE12 , the relationship of equation (5) is obtained.

That this voltage difference is obtained at both ends of the voltage emitter resistor R ₁₃ having a positive temperature coefficient which is proportional to T, which R ₁₂ / R
_By multiplying by _{13 and} adding to the temperature coefficient of the base-emitter voltage V _BE having a negative temperature coefficient of the amplification transistor Q ₁₃ , the temperature coefficient of the collector voltage V _R of the transistor Q ₁₃ is reduced to zero or any desired value. can do.

By connecting the resistor R _14, R ₁₅ in parallel with the temperature compensation voltage trimming circuit 1 _a resistor R ₁₃ Alternatively, it is possible to trim the correction of the temperature characteristic by set by changing the current.

The diodes D ₁ and D ₂ are a kind of fuse ROM that can be destructively short-circuited by applying a current.

While the collector of the transistor Q ₁₃ is an output voltage V _R of the constant-voltage circuit, over feedback at the operational amplifier A ₁ as the emitter voltage V _E of the voltage and the transistor Q ₁₄ becomes equal.

Thus current I ₀ obtained by dividing the voltage V _R at the resistor R ₁₆ flows through the transistor Q _14.

The capacitor C starts charging when the short-circuit switch S _s is turned off by the constant current I ₀ , and the voltage V _{C at} both ends of the capacitor _C becomes t.
Is the time, Equation (6) is obtained.

This voltage is inverted output signal S ₀ of the comparator A ₂ when so is compared with a reference voltage V _r of the capacitor voltage V _C is equal to the comparison voltage V _r in the comparator A _2.

That is, the delay time t of the delay circuit 7 is expressed by the following equation (7).

Here, the compensation of the temperature coefficient of the current V _R / R ₁₆ of the reference voltage V so _R can be a desired temperature coefficient, the transistor Q ₁₄ by equalizing the temperature characteristics of this and R ₁₆ as previously described can do.

Further using a voltage source of reference voltage V _r having no temperature coefficient as V _r, ignoring the temperature coefficient of the capacitor C since the temperature coefficient of the normal LSI internal capacitor is small, delay time t does not depend on temperature constant It can be.

Of course, the temperature characteristics of the voltage _Vr can be determined so as to strictly correct the comparison voltage _Vr and the temperature coefficient of the capacitor C.

Variation Δt mainly C · because determined by the variation of R ₁₆ delay time by by trimming the value of the resistor R ₁₆ in accordance with a variation ΔC of the capacitor C sets the CR product to a predetermined value t in this case the delay time t Can be eliminated.

Current resistance R ₁₇ to R _19, the diode D ₃ to D ₅ is a trimming circuit for this.

The present embodiment is different from the first embodiment in that the value of the current source whose temperature coefficient has been corrected is set so as to correct the variation ΔC of the built-in capacitor C.

This example can be applied to a circuit for determining a time constant of a one-shot multiplier, an oscillator, a filter, or the like, in addition to the delay circuit 7, and can produce a time constant having no temperature characteristics and little variation.

The present invention is not limited to FIGS. 1 and 2, but may be a combination of the two as appropriate, various reference voltage circuits, memory means, or current combining means.

〔The invention's effect〕

As described above, according to the present invention, trimming is performed using an element inside the LSI to set a constant current without a temperature coefficient or corrected, and trimming of the absolute value of the current or the variation of the time constant with the built-in capacitance. Thus, a reference current source circuit having an output constant current with good accuracy and good temperature characteristics can be obtained.

This means that a high-precision current output and time constant can be created without the need for an external high-performance resistor on the LSI. In addition to being able to be used and improving the degree of integration, there is an industrially significant effect that a highly accurate external resistor is not required.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, and FIG. 2 is a circuit diagram of a second embodiment of the present invention. 1,1 _a …… Temperature characteristic compensation voltage trimming circuit, 2,2 _a ……
Constant current trimming circuit, 3,3 _a ...... trimming setting circuit,
4 ... register, 5 ... EPROM, 6 ... writing circuit, 7 ...
… Delay circuit, d, d _{1 to} d ₃ …… Trimming setting signal, I _I
…… Constant current, I _O …… Output constant current, Q _{1 to} Q ₃ …… Transistor, R _{1 to} R ₃ …… Current setting resistance, R _V , R _D …… Division resistance, S ₁
~S ₃ ...... current switch, S _W ...... V _B select switch,
T ₀ , T _0a …… Output terminal, V _B , V _R …… Reference voltage, V _Z …… Constant voltage.

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01L 27/04

Claims (2)

(57) [Claims] 1. A temperature characteristic compensating voltage trimming circuit for trimming a divided voltage value of an internal constant voltage to output a reference voltage, and a current setting resistor at an emitter (source) which receives the divided voltage value at a common control terminal. A plurality of transistors, a plurality of current switches each having one end connected to the collector (drain) of the transistor, and the other end supplying an output current to a common output terminal; outputting a trimming setting signal to trim the reference voltage; And a trimming setting circuit having a one-time write memory means for setting the trimming of the LSI. A temperature-compensation voltage trimming circuit having a bandgap reference voltage source for outputting a predetermined reference voltage; an operational amplifier for inputting the reference voltage at one end and feeding back a feedback voltage to the other end; An output signal of the operational amplifier is input to a control terminal, an emitter (source) is connected to a current setting resistor capable of trimming, the feedback voltage is generated, and a collector (drain) supplies an output constant current to an output terminal. And a trimming setting circuit having a one-time write memory means for outputting a trimming setting signal to perform trimming of the reference voltage and trimming setting of the current switch.