CN105049047A - Reference voltage driving circuit of analogue-to-digital converter - Google Patents

Abstract

The invention discloses a reference voltage driving circuit of an analogue-to-digital converter. The reference voltage driving circuit is characterized by comprising two reference voltage driving modules and two switched capacitor networks; the two switched capacitor networks are correspondingly connected with the two reference voltage driving modules. According to the reference voltage driving circuit of the analogue-to-digital converter, the relative establishment accuracy of the reference voltage driving circuit outputting voltage signals is improved, and therefore, higher-speed and higher-accuracy establishment is realized under the same power consumption.

Description

A kind of drive circuit of analog to digital converter reference voltage

Technical field

The present invention relates to semiconductor integrated circuit technical field, particularly a kind of drive circuit of analog to digital converter reference voltage.

Background technology

In the past few decades, integrated circuit technique obtains swift and violent development.Electronic system particularly headed by communication, the direction towards two-forty, high-performance, high integration, low cost constantly advances.This just has higher requirement to the modules in system.As analog to digital converter.While system requirements improves the requirement such as sampling rate, quantified precision of analog to digital converter, also wish the conversion efficiency improving analog to digital converter, reduce its power consumption.

In traditional high sampling rate analog to digital converter, internal reference voltage drive circuit is usually used to improve the driving precision of reference voltage.Along with the raising of sampling rate, the voltage of reference voltage circuit can recovery time shorten.Reference voltage circuit can only consume more electric current to what improve output voltage and set up speed, ensures the precision of analog to digital converter.

Summary of the invention

For solving above-mentioned existing shortcoming, main purpose of the present invention is the drive circuit providing a kind of analog to digital converter reference voltage, relatively set up precision by what improve reference voltage driving circuit output voltage signal, under same power consumption, realize the foundation that speed is faster, precision is higher.

For reaching above-described object, following technical scheme taked by the drive circuit of a kind of analog to digital converter reference voltage of the present invention:

A drive circuit for analog to digital converter reference voltage, is characterized in that: comprise two reference voltage driver modules and two switched capacitor networks; Described two switched capacitor networks and described two corresponding connections of reference voltage driver module.

Described reference voltage driver module comprises Vt drive circuit Vtdriver and Vb drive circuit Vbdriver; The output of described Vt drive circuit and Vb drive circuit has low impedance characteristics; The input and output voltage gain of described drive circuit is about 1.

Described switched capacitor network, comprises Vt switched capacitor network and Vb switched capacitor network; Described Vt switched capacitor network comprises switch S t1, switch S t2, switch S t3, switch S t4, electric capacity Ctp, electric capacity Ctn, electric capacity Ct, electric capacity Ctx; Described Vb switched capacitor network comprises switch Sb 1, switch Sb 2, switch Sb 3, switch Sb 4, electric capacity Cbp, electric capacity Cbn, electric capacity Cb, electric capacity Cbx, and described Vt switched capacitor network is connected to the output of Vt drive circuit; Described Vb switched capacitor network is connected to the output of Vb drive circuit.

Described switching capacity Ctp, electric capacity Ctn, electric capacity Ct, its negative plate is connected to the output of Vt drive circuit by switch S t1, switch S t2, switch S t3, the positive plate of electric capacity Ctp is connected to Vopa, p, the positive plate of electric capacity Ctn is connected to Vopa, n, and the positive plate of electric capacity Ct is connected to ground, the negative plate of electric capacity Ctx is connected to input common mode electrical level Vicm by switch S t4, and the positive plate of electric capacity Ctx is connected to ground; Total capacitance of electric capacity Ctp and electric capacity Ctn is N*Cs0, and wherein N*Cs0 is the total capacitance of sampling capacitance of sample circuit, is on average divided into the equal small capacitances Cs0 of N number of capacitance; The capacitance of electric capacity Ctp is determined at the input voltage value of sampling phase by ADC; Hypothetical reference voltage Vref=Vt-Vb, the anode of ADC is input as Vip=Vi+Vicm, and the negative terminal of ADC is input as Vin=-Vi+Vicm, and wherein the span of Vi is between ± Vref/2, and Vicm is the common mode incoming level of ADC; The capacitance of electric capacity Ctp can be expressed as M*Cs0 ≈ Vi/Vref*N*Cs0+N*Cs0/2, and namely the span of M is 0 ~ N; The capacitance of described electric capacity Ctn is (N-M) * Cs0; The capacitance of described electric capacity Ct is | N-2*M|*Cs0; The capacitance of described electric capacity Ctx is (N-|N-2*M|) * Cs0.

Described switching capacity Cbp, electric capacity Cbn, electric capacity Cb, its negative plate is connected to the output of Vb drive circuit by switch Sb 1, switch Sb 2, switch Sb 3, the positive plate of electric capacity Cbp is connected to Vopa, p, the positive plate of electric capacity Cbn is connected to Vopa, n, and the positive plate of electric capacity Cb is connected to ground, the negative plate of electric capacity Cbx is connected to input common mode electrical level Vicm by switch Sb 4, and the positive plate of electric capacity Cbx is connected to ground; Total capacitance of electric capacity Cbp and electric capacity Cbn is N*Cs0, and wherein N*Cs0 is total capacitance of the sampling capacitance of sample circuit; The capacitance of Cbp inputs Vin=-Vi+Vicm by the negative terminal of ADC and determines; The capacitance of electric capacity Cbp can be expressed as (N-M) * Cs0; The capacitance of described electric capacity Cbn is M*Cs0; The capacitance of described electric capacity Cb is | N-2*M|*Cs0; The capacitance of described electric capacity Cbx is (N-|N-2*M|) * Cs0.

When switched capacitor network is connected with Vt drive circuit, Vb drive circuit, the quantity of electric charge that under compensation ADC varying input signal voltage magnitude, switching network needs, the difference of the output charge amount of reduction Vt drive circuit, Vb drive circuit.

Adopt the invention of as above technical scheme, there is following beneficial effect:

The present invention sets up precision relatively by raising reference voltage driving circuit output voltage signal, under same power consumption, realizes the foundation that speed is faster, precision is higher.

Accompanying drawing explanation

Fig. 1 is the low power consumption high-precision sheet internal reference voltage drive schemes of high-speed ADC of the present invention.

Fig. 2 is the present invention when being applied in MDAC, the connected mode of reference voltage driver and sampling capacitance, additional capacitor.

When Fig. 3 (a) is for reference voltage driver drives high level reference voltage, the comparison diagram of traditional circuit and circuit output charge amount of the present invention.

When Fig. 3 (b) is for reference voltage driver drives low level reference voltage, the comparison diagram of traditional circuit and circuit output charge amount of the present invention.

Embodiment

In order to further illustrate invention, be described further below in conjunction with accompanying drawing:

As shown in Figure 1, the drive circuit of a kind of analog to digital converter reference voltage of the present invention, circuit module comprises two reference voltage driver modules and switched capacitor network.Voltage driven module is voltage driven module Vtdriver, voltage driven module Vbdriber respectively, is respectively used to drive reference voltage high potential and electronegative potential.The voltage gain of this driver is 1.Switching capacity networking comprises Vt switched capacitor network and Vb switched capacitor network.Vt switched capacitor network is by switch S t1, switch S t2, switch S t3, switch S t4, and electric capacity Ctp, electric capacity Ctn, electric capacity Ct, electric capacity Ctx form.Vb switched capacitor network is by switch Sb 1, switch Sb 2, switch Sb 3, switch Sb 4, and electric capacity Cbp, electric capacity Cbn, electric capacity Cb, electric capacity Cbx form.Wherein electric capacity Ctp, electric capacity Ctn, electric capacity Cbp, electric capacity Cbn are electric capacity intrinsic in traditional MDAC circuit.And electric capacity Ct, electric capacity Ctx, electric capacity Cb, electric capacity Cbx are the electric capacity that the present invention increases.

Suppose that the electric capacity that sampling capacitance is Cs0 by N number of capacitance forms, total capacitance value is designated as Cs, and its size is N*Cs0.Electric capacity Ctp and electric capacity Cbp, electric capacity Ctn and electric capacity Cbn, electric capacity Ct and electric capacity Ctx, electric capacity Cb, electric capacity Cbx, each group in these four groups of electric capacity all has the electric capacity that N number of capacitance is Cs0.

Suppose that the low and high level of the reference voltage of analog to digital converter is Vt, Vb respectively, its expression formula is

$Vt=\frac{Vref}{2}+Vicm$

$Vb=-\frac{Vref}{2}+Vicm$

Wherein, Vicm is the intermediate voltage value of height reference voltage.At sampling instant point, the Differential Input of analog to digital converter is designated as anode input Vip and negative terminal input Vin, can be expressed as

$Vip=Vi+Vicm,(Vi\∈\[-\frac{Vref}{2},\frac{Vref}{2}\])$

$Vin=-Vi+Vicm,(Vi\∈\[-\frac{Vref}{2},\frac{Vref}{2}\])$

Wherein, Vi is the AC signal of analog to digital converter single ended input.Comparator, according to the magnitude of voltage of Differential Input, obtains quantized result M.This quantized result represents, amplifies phase place in surplus, and have M to be connected to the high potential of reference voltage at the sampling capacitance of input anode, namely the capacitance of Ctp equals M*Cs0; Have N-M to be connected to the electronegative potential of reference voltage at the sampling capacitance of input anode, namely the capacitance of Cbp equals (N-M) * Cs0.Correspondingly, have N-M to be connected to the high potential of reference voltage at the sampling capacitance of input negative terminal, namely the capacitance of Cbn equals M*Cs0; Have M to be connected to the electronegative potential of reference voltage at the sampling capacitance of input negative terminal, namely the capacitance of Ctn equals (N-M) * Cs0.The relation of quantized result M and input voltage can be expressed as

$M\≈\frac{N}{2}+\frac{Vi}{Vref}*N$

The span of M is 0 ~ N.

Under compensating different input voltage condition, reference voltage driving circuit is to the discharge and recharge quantity of electric charge of capacitance network, and the present invention increases variable, Mp.The electric capacity Cs0 number that Mp is electric capacity Ct, electric capacity Cb is connected to reference voltage high potential by switch S t3, Sb3 in surplus amplification phase place.Mp is determined by following expression formula

Mp＝|N-2*M|

The input signal of Mp and analog to digital converter closes and is

$Mp\≈2N\left|\frac{Vi}{Vref}\right|$

Similarly, N-Mp electric capacity Cs0 is had to be connected to reference voltage electronegative potential by switch S t4, switch Sb 4.

Fig. 2 follows phase place in input, the connected mode of the electric capacity in Fig. 1.The positive plate of electric capacity Ctp, electric capacity Cbp is connected to the input common mode electrical level Vopa of operational amplifier, cm by switch S 9; The negative plate of electric capacity Ctp, electric capacity Cbp is connected to the anode input Vip of analog to digital converter by switch S 5.The positive plate of electric capacity Ctn, electric capacity Cbn is connected to the input common mode electrical level Vopa of operational amplifier, cm by switch S 10; The negative plate of electric capacity Ctn, electric capacity Cbn is connected to the negative terminal input Vin of analog to digital converter by switch S 5.The positive plate of electric capacity Ct, electric capacity Ctx, electric capacity Cb, electric capacity Cbx is all connected to ground, and negative plate is connected to the input common mode electrical level Vicm of analog to digital converter respectively by switch S 7, S8.

Suppose at sampling instant point, the single ended input alternating voltage of analog to digital converter is Vi, and quantized result is M.Amplify phase place in surplus, the switch S 9 in Fig. 2, switch S 10, switch S 11 disconnect.Under the effect of operational amplifier, node Vopa, p, node Vopa, n void are short.Can think that the current potential of these two nodes is Vopa, cm.

So the anode input of analog to digital converter is connected to the electric capacity Ctp of reference voltage high level, and the total charge dosage Δ Qtp extracted from reference circuit is

$\begin{array}{c}\mathrm{\Δ}Qtp=(Vt-Vip)*M*Cs0\\ \≈Cs*\frac{Vref}{4}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2})\end{array}$

The negative terminal input of analog to digital converter is connected to the electric capacity Ctn of reference voltage high level, and the total charge dosage Δ Qtn extracted from reference circuit is

$\begin{array}{c}\mathrm{\Δ}Qtn=(Vt-Vin)*(N-M)*Cs0\\ \≈Cs*\frac{Vref}{4}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2})\end{array}$

The anode input of analog to digital converter is connected to the low level electric capacity Cbp of reference voltage, and the total charge dosage Δ Qbp extracted from reference circuit is

$\begin{array}{c}\mathrm{\Δ}Qbp=(Vb-Vip)*(N-M)*Cs0\\ \≈-Cs*\frac{Vref}{4}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2})\end{array}$

The negative terminal input of analog to digital converter is connected to the electric capacity Cbn of reference voltage high level, and the total charge dosage Δ Qbn extracted from reference circuit is

$\begin{array}{c}\mathrm{\Δ}Qbn=(Vb-Vin)*M*Cs0\\ \≈-Cs*\frac{Vref}{4}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2})\end{array}$

Amplify phase place in surplus, electric capacity Ct, electric capacity Cb are respectively from the high level, the low level output that are connected to Vicm and are switched to reference voltage circuit.Namely Fig. 2 breaker in middle S7, S8 disconnect, and switch S t3, switch S t4, switch Sb 3, switch Sb 4 close.The total charge dosage Δ Qct that electric capacity Ct extracts from reference circuit is

ΔQct＝(Vt-Vicm)*Mp*Cs0

≈Cs*|Vi|

The total charge dosage Δ Qcb that electric capacity Cb extracts from reference circuit is

ΔQcb＝(Vb-Vicm)*Mp*Cs0

≈-Cs*|Vi|

So, traditional reference circuit needs the total charge dosage Δ Qt0 provided for electric capacity Ctp, electric capacity Ctn to be

$\begin{array}{c}\mathrm{\Δ}Qt0=\mathrm{\Δ}Qtp+\mathrm{\Δ}Qtn\\ \≈Cs*\frac{Vref}{2}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2})\end{array}$

Increase after electric capacity Ct is connected to reference voltage circuit, reference voltage high potential vto needs the total charge dosage provided for switching capacity to be

$\begin{array}{c}\mathrm{\Δ}Qt=\mathrm{\Δ}Qtp+\mathrm{\Δ}Qtn+\mathrm{\Δ}Qct\\ \≈Cs*\frac{Vref}{2}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2}+2\frac{\left|Vi\right|}{Vref})\end{array}$

The total charge dosage minimum value that traditional reference circuit vto exports is 0, and corresponding input Vi is exporting total charge dosage maximum is corresponding input vi is 0.Minimax quantity of electric charge difference is the total charge dosage minimum value that reference circuit of the present invention exports is corresponding input Vi is 0, exporting total charge dosage maximum is corresponding input vi is minimax quantity of electric charge difference is as shown in Fig. 3 (a).When block curve in figure is traditional reference voltage driving circuit driving high level, each switch needs the total amount of electric charge provided.Dashed curve is drive scheme of the present invention, and when drive circuit drives high level, each switch needs the total amount of electric charge provided.

Similarly, can obtain conventional reference circuit needs the total charge dosage Δ Qb0 provided for electric capacity Cbp, electric capacity Cbn to be

$\begin{array}{c}\mathrm{\Δ}Qb0=\mathrm{\Δ}Qbp+\mathrm{\Δ}Qbn\\ \≈-Cs*\frac{Vref}{2}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2})\end{array}$

Increase after electric capacity Cb is connected to reference voltage circuit, reference voltage high potential vbo needs the total charge dosage provided for switching capacity to be

$\begin{array}{c}\mathrm{\Δ}Qb=\mathrm{\Δ}Qbp+\mathrm{\Δ}Qbn+\mathrm{\Δ}Qcb\\ \≈-Cs*\frac{Vref}{2}*(1-4*\frac{{\mathrm{Vi}}^2}{{\mathrm{Vref}}^2}+2\frac{\left|Vi\right|}{Vref})\end{array}$

The total charge dosage minimum value that traditional reference circuit vbo exports is 0, and corresponding input Vi is exporting total charge dosage maximum is corresponding input vi is 0.Minimax quantity of electric charge difference is the total charge dosage minimum value that reference circuit of the present invention exports is corresponding input Vi is 0, exporting total charge dosage maximum is corresponding input vi is minimax quantity of electric charge difference is as shown in Fig. 3 (b).When block curve in figure is traditional reference voltage driving circuit driving high level, each switch needs the total amount of electric charge provided.Dashed curve is drive scheme of the present invention, and when drive circuit drives high level, each switch needs the total amount of electric charge provided.

Although the maximum output charge amount of Voltag driving circuit of the present invention is larger than traditional circuit.But as long as ensure under different input voltage, reference voltage is set up between error enough little in official hour.Voltag driving circuit of the present invention does not require that Voltage Establishment arrives absolute precision, and requires that Voltage Establishment arrives relative accuracy.The output charge measures of dispersion of circuit of the present invention is traditional circuit can consume under same power consumption, the condition of same settling time, obtain 4 times and relatively set up precision to traditional circuit.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (6)

1. a drive circuit for analog to digital converter reference voltage, is characterized in that: comprise two reference voltage driver modules and two switched capacitor networks; Described two switched capacitor networks and described two corresponding connections of reference voltage driver module.

2. the drive circuit of a kind of analog to digital converter reference voltage according to claim 1, is characterized in that: described reference voltage driver module comprises Vt drive circuit Vtdriver and Vb drive circuit Vbdriver; The output of described Vt drive circuit and Vb drive circuit has low impedance characteristics; The input and output voltage gain of described drive circuit is about 1.

3. the drive circuit of a kind of analog to digital converter reference voltage according to claim 1, is characterized in that: described switched capacitor network, comprises Vt switched capacitor network and Vb switched capacitor network; Described Vt switched capacitor network comprises switch S t1, switch S t2, switch S t3, switch S t4, electric capacity Ctp, electric capacity Ctn, electric capacity Ct, electric capacity Ctx; Described Vb switched capacitor network comprises switch Sb 1, switch Sb 2, switch Sb 3, switch Sb 4, electric capacity Cbp, electric capacity Cbn, electric capacity Cb, electric capacity Cbx, and described Vt switched capacitor network is connected to the output of Vt drive circuit; Described Vb switched capacitor network is connected to the output of Vb drive circuit.

4. the drive circuit of a kind of analog to digital converter reference voltage according to claim 3, it is characterized in that: described switching capacity Ctp, electric capacity Ctn, electric capacity Ct, its negative plate is connected to the output of Vt drive circuit by switch S t1, switch S t2, switch S t3, the positive plate of electric capacity Ctp is connected to Vopa, p, the positive plate of electric capacity Ctn is connected to Vopa, n, the positive plate of electric capacity Ct is connected to ground, the negative plate of electric capacity Ctx is connected to input common mode electrical level Vicm by switch S t4, and the positive plate of electric capacity Ctx is connected to ground; Total capacitance of electric capacity Ctp and electric capacity Ctn is N*Cs0, and wherein N*Cs0 is the total capacitance of sampling capacitance of sample circuit, is on average divided into the equal small capacitances Cs0 of N number of capacitance; The capacitance of electric capacity Ctp is determined at the input voltage value of sampling phase by ADC; Hypothetical reference voltage Vref=Vt-Vb, the anode of ADC is input as Vip=Vi+Vicm, and the negative terminal of ADC is input as Vin=-Vi+Vicm, and wherein the span of Vi is between ± Vref/2, and Vicm is the common mode incoming level of ADC; The capacitance of electric capacity Ctp can be expressed as M*Cs0 ≈ Vi/Vref*N*Cs0+N*Cs0/2, and namely the span of M is 0 ~ N; The capacitance of described electric capacity Ctn is (N-M) * Cs0; The capacitance of described electric capacity Ct is | N-2*M|*Cs0; The capacitance of described electric capacity Ctx is (N-|N-2*M|) * Cs0.

5. the drive circuit of a kind of analog to digital converter reference voltage according to claim 3, it is characterized in that: described switching capacity Cbp, electric capacity Cbn, electric capacity Cb, its negative plate is connected to the output of Vb drive circuit by switch Sb 1, switch Sb 2, switch Sb 3, the positive plate of electric capacity Cbp is connected to Vopa, p, the positive plate of electric capacity Cbn is connected to Vopa, n, the positive plate of electric capacity Cb is connected to ground, the negative plate of electric capacity Cbx is connected to input common mode electrical level Vicm by switch Sb 4, and the positive plate of electric capacity Cbx is connected to ground; Total capacitance of electric capacity Cbp and electric capacity Cbn is N*Cs0, and wherein N*Cs0 is total capacitance of the sampling capacitance of sample circuit; The capacitance of Cbp inputs Vin=-Vi+Vicm by the negative terminal of ADC and determines; The capacitance of electric capacity Cbp can be expressed as (N-M) * Cs0; The capacitance of described electric capacity Cbn is M*Cs0; The capacitance of described electric capacity Cb is | N-2*M|*Cs0; The capacitance of described electric capacity Cbx is (N-|N-2*M|) * Cs0.

6. the drive circuit of a kind of analog to digital converter reference voltage according to claim 3, it is characterized in that: when switched capacitor network is connected with Vt drive circuit, Vb drive circuit, the quantity of electric charge that under compensation ADC varying input signal voltage magnitude, switching network needs, the difference of the output charge amount of reduction Vt drive circuit, Vb drive circuit.