JPH02275664A - Reference-voltage generating circuit - Google Patents

Abstract

PURPOSE:To enable trimming even when the constant voltage of a constant voltage source is made higher than desired reference output voltage by installing an output voltage selector for selecting a voltage dividing path. CONSTITUTION:An output voltage selector 4 is inserted between a nodal point B, at which the output terminal of an internal reference voltage section 1 and a resistance section 6 for trimming are connected, and the input terminal of an output buffer section 2. The i1-i32 and T6-T10 and output terminal S of the output voltage selector 4 correspond to j1-j32 and T1-T5 and an output terminal F respectively, the input terminal i1 is connected at the nodal point B, and i2-i32 are connected to nodal points N1-N31 respectively. Consequently, the same internal reference voltage VB or one of the divided voltage is selected as selective output voltage VS at the output terminal S by digital control signals input to the terminals T6-T10. Accordingly, reference output voltage lower than internal constant voltage can also be trimmed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reference voltage generation circuit, and more particularly to a reference voltage generation circuit for an integrated circuit having a trimming resistor section.

[Conventional technology]

FIG. 2 is a circuit diagram of an example of a conventional reference voltage generating circuit.

The output buffer section 2 is a voltage follower circuit that outputs one times the internal reference voltage VB from the internal reference voltage section 1.

The feedback voltage selector 3 is used for selection at the output of the internal reference voltage section 1.

The decoder receives digital signals from input terminals T1 to T.

input to drive the electronic switch.

The constant voltage VT of the constant voltage source 5 is determined by the threshold voltages of the enhancement type transistor and the dabrella silane type transistor inside the internal reference voltage section 1.

Resistors Ra, Rb, and r are the respective resistors of the trimming resistor section 6, and here, one each of Ra and Rb and 32 r are used.

The contact points Nl''N3z between the respective resistors are connected to the input terminals jt-j3z of the selector 3 in order from the top.

FIG. 3 is a circuit diagram of the feedback voltage selector of FIG. 2.

The feedback voltage selector 3 is connected to a row gate section 3R and a column gate section 3c according to input signals from digital input terminals T1 to T.
It drives a decoder and has a matrix gate section 3M of 8×4 transfer gates.

This reference voltage generation circuit is connected to a node of the trimming resistor section 6, for example, jl connected to N1 or jl7 connected to N1γ.
is selected by the selector 3, the output balance section 20
The reference output voltage Vj can be easily obtained.

Further, from these voltages, it is possible to find the node number that is closest to the predetermined reference output voltage ■j.

The internal reference voltage of the internal reference voltage section 1 is VB, the constant voltage of the constant voltage source 5 is VT, the reference output voltage of the output buffer section 2 is ■j, and the j-th input voltage terminal Jj selected by the selector 3
(however, j = 1 to 32), the offset voltage of the output buffer section 2) [pressure is VIO% When the selection number j is 1 and 17, the reference output voltage ■ is Vl p ■ 17, then the following Equations (1) to (5) are obtained.

Vj=Vs+Vro --(1)
VB=(1+(Ra+(k-1)r)/(Rb+(33
-k)r))Vr ・---(2)th (1), (
According to formula 21, Vj=(1+(Ra+(k 1)r)/(Rb+(3
3-k)r])Vt+Vxo-(3) When j=1.17, ■j=■l, ■17, so the equation (3) becomes the
), formula (5) is obtained.

V 1== (1+Ra/ (几b+3z r ) )
VT +V 10... (4) Vly=(1+(Ra+16 r)/(LCb+16
r)) Vr + Vz.

(5) In Figure 2, the actual value is 0.48 kΩ.
.

Using Ω for Rb = 10.212 kΩ and r = 0.213, and assuming the desired reference output voltage Vj to be 3.1v, equation (6) is obtained from equations +31, +4) and (5). .

j=(251,1+4Vty 85Vl)/(3,1
-5vl+4Vly) +++ (6) Also, the first
From equations 4) and 5), equations +71 and (81) are obtained.

VI? =1.28525VT+VIO-・” (7)
v1 = 1.0282vT 1.・・・・・・
(8) Now VT=3. When OV, VX□=10 mV, j=1.1 from equations (7) and (8), and v0=λ099VK from equation (3).

Also, if VT = 1.9 V and "to = -20 mV," No. (6).

According to equations (7) and (8), j = 3o, 9 and the (3rd
) From the formula ■.

=3.106V.

Therefore, in this reference voltage generation circuit, the constant voltage (1) is 1.9V~
Trimming is possible with the selector 3 between 3.070 and 3.070.

That is, the constant voltage vT is the desired reference output voltage ■.

Trimming was performed when the voltage was lower than that.

[Problem to be solved by the invention]

The conventional reference voltage generation circuit described above has a drawback that trimming cannot be performed when the constant voltage of the constant voltage source is higher than the desired reference output voltage.

An object of the present invention is to provide a reference voltage generation circuit that can also trim a reference output voltage lower than an internal constant voltage.

[Failure to solve the problem]

The reference voltage generation circuit of the present invention has an internal reference voltage section that inputs a constant voltage and a feedback voltage, operationally amplifies them, and outputs an internal reference voltage, and a plurality of trimming resistors connected in series through nodes to generate the internal reference voltage. a trimming resistor unit that divides the voltage; a feedback voltage selection unit that selects one voltage at the node as the feedback voltage; and a reference output voltage that selects one of the internal reference voltage or the voltage at the node and outputs it as a reference output voltage. It is configured to include a selection section.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

The reference voltage generation circuit differs in that an output voltage selector 4 is inserted between the node B where the output terminal of the internal reference voltage section 1 and the trimming resistor section 6 are connected in FIG. 2, and the input terminal of the output buffer section 2. Other than this point, it is the same as the conventional reference voltage generation circuit.

The output voltage selector 4 is the same circuit as the feedback voltage selector 3 in FIG. There is.

Input terminal i1 is connected to node B, and input terminals 12 to isx are connected to nodes N1 to N31, respectively.

Therefore, depending on the digital control signal input to the terminals T6 to 'l'to, the same internal reference voltage VB as the conventional one explained in FIG. 2 or one of its divided voltages is selected as the selected output voltage ■s at the output terminal S. be done.

Next, the operation of the circuit will be explained.

The internal reference voltage of the internal reference voltage section 1 is set to vB%, the constant voltage of the constant voltage source 5 is set to vT1, the reference output voltage of T1 output is set to Vj, and the feedback voltage selector 3, which inputs each divided voltage of the trimming resistor section 6, selects j-th input terminal number" (however, j
= 1 to 32), the i-th input terminal number selected by the output voltage selector 4 is i (where i = 2 to 32), and the offset voltage of the output buffer section 2 is VIO, then the following (91,
(Equation 11 is obtained.

VB = ((Ra 10 b + 32 r) / [几 b + (a 3
Dr)) VT・・・・・・ (9) Vj=(C几り+(34=)r)10Lb+(33−
j) r)) VT+VIO...0.1 Here, if i = l, it will be the same as the case explained in the conventional example in Fig. 2, so when 1 = 1117, Vj = V1°V
j7, Ra=0.48 is Ω, R=0.212 is Ω, r=0.213 is Ω, and the desired reference output voltage Vj is 3.1■, then the formula (1v) is obtained.

j=(251,1+4V+y85V+)/(3,
15V1+4V17) --(11) This is the same equation as equation (6) explained in the conventional example.

As an example, the case where ZIV≦■T≦3.4■ will be explained.

+7+, from formula (8), Vxo=O and V17
=4.3699V.

Vx=3.4959V and fx ri (to 6!')j=-
9, 22 and fx, 1≦j≦32 is not satisfied, i = l
It is impossible to trim.

Therefore, when i>1, trimming is performed when the internal reference voltage is higher than the reference output voltage.

For example, K that allows trimming at VT = 3.4V only needs to satisfy ■l≦3.1v when j = 1 in the α1 equation, so if VIo = O, the equation (10-1) is obtained. It will be done.

i≧8,05 ・・・・・・
(10-1) Therefore, if i = / 0, then from the α1 formula, the 04th is the mari j = 1, 17 O, Vj = V
+ , Vj7 tel, and when VIO=0, equations (13 and (14)) are obtained.

Vj = ((Rb +24.r)/(Rb +(33
−j)R) )Vt+Vxo ・・・・・・ α
Vl=0.90VT-・”
Q31Ly = 1.1 25VT
−・・04) Here vT=
If it is 3.4v, then formulas Q31 and Q41 (yoF) V
+ = 3.06v, v17 = 3.825■, so
Equation (11) j=2. o3, therefore, if ``=2, then V = 3.099V from the α3 equation.

Here, VT=2. If it is IV, from the αth country, formula C14), Vl ' 1.85 V-Vj7 = Z3625
V The Alkara, according to equation (11), j = 3z2, so if j = 32, then from equation α3, Vz = 3.086 V
become.

Therefore, trimming is possible even when ZIV≦vT≦3.4■, and a constant voltage V higher than the desired reference output voltage o
Trimming is also possible with T.

Note that both selectors 3 and 4 are connected to the column gate section 3c in FIG.
Instead of υ, a logic circuit using an inverter, NAND, and transformer 7 agate may be used.

〔Effect of the invention〕

As explained above, the present invention provides an output voltage selector for selecting a voltage dividing path between the trimming resistor section and the input terminal of the next-stage output buffer section, so that the constant voltage of the constant voltage source can be adjusted to a desired level. This has the effect that trimming can be performed even when the output voltage is higher than the reference output voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of an example of a conventional reference voltage generating circuit, and FIG. 3 is a circuit diagram of the feedback voltage selector of FIG. 2. 1...Internal reference voltage section, 2...Output balance section, 3...Feedback voltage selector, 4...
... Output voltage selector, 5 ... Constant voltage source, 6
...Trimming resistance section, v8...Internal reference voltage, VF...Feedback voltage, Vj...
...Reference output voltage, Vs...Selected output voltage, V
T... Constant voltage. Agent Patent Attorney Shinsuke Uchihara 3

Claims (1)

[Claims] an internal reference voltage section that inputs a constant voltage and a feedback voltage, operationally amplifies them, and outputs an internal reference voltage; a trimming resistor section that divides the internal reference voltage by connecting a plurality of trimming resistors in series through nodes; The feedback voltage selection unit selects one voltage at a node as the feedback voltage, and the reference output voltage selection unit selects one of the internal reference voltage or the voltage at the node and outputs it as a reference output voltage. Reference voltage generation circuit.