MM1089 [MITSUMI]

Sensor Amplifier; 传感器放大器


型号：	MM1089
厂家：	MITSUMI ELECTRONICS, CORP.
描述：	Sensor Amplifier 传感器放大器传感器放大器
文件：	总9页 (文件大小：215K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

Sensor Amplifier MM1089

MITSUMI

Sensor Amplifier

Monolithic IC MM1089

Outline

This IC is an amplifier with a high-impedance differential input, which can be used in high-CMR instrumentation.

Particularly when amplifying signals from a high-impedance or high-bias signal source, often signals are buried

in noise, making amplification difficult. This IC amplifies only the signal, and the noise is suppressed rather than

amplified, making it effective for use where noise is prominent or with high-impedance signal sources.

Features

1. Battery charge/discharge current detection

(for laptops, word processors, etc)

2. Signal amplifiers for magnetic sensors, pressure sensors, strain gauges

3. Instrumentation amps

80dB min., 100dB typ.

Except 10MΩ

3~ 100

4. Broad input range

-0.3V~VCC+0.3V

5. Two internal channels

Package

SOP-18A (MM1089XF)

Applications

1 Detection of battery charge/discharge current (for notebook computers, word processors etc)

2 Amplification of magnetic sensor, pressure sensor, strain gauge, other signals

3 Instrumentation amp

Sensor Amplifier MM1089

MITSUMI

Pin Assignment

Input range

switching 1

¹⁸VCC

Input range

switching 2

+IN1

Rg1

¹⁶+IN2

Rg2

IN1

IN2

Rs1

OUT1

Rs2

OUT2

O.COM2

¹⁰O.COM2

O.COM1

GND

Pin no.

Pin name

Function

AMP1 Input voltage range switching

Input range switching 1

INCHG1

IN1+

Hi : 1.8V~V^CC+0.3V LO :

AMP1 +Input

-0.3V~VCC-1.8V

Rg1+

AMP1 Resistance to set the Rg gain

Rg1-

IN1

AMP1

-Input

Rs1

OUT1

O.COM1

GND

AMP1 Resistance to set the Rs gain

AMP1 Resistance to set the Rs gain, output 1

AMP1 Common output

Ground

O.COM2

OUT2

Rs2

AMP2 Common output

AMP2 Resistance to set the Rs gain, output 2

AMP2 Resistance to set the Rs gain

IN2-

AMP2 -Input

Rg2-

AMP2 Resistance to set the Rg gain

AMP2 +Input

Rg2+

IN2+

Input range switching 2

INCHG2

AMP2 Input voltage range switching

Hi : 1.8V~V^CC+0.3V Lo :

Power supply input

-0.3V~VCC-1.8V

V^CC

Sensor Amplifier MM1089

MITSUMI

Equivalent Circuit Diagram

(Ta=25°C)

Absolute Maximun Ratings

Item

Symbol

T^OPR

T^STG

V^CC

Ratings

20~+70

40~+125

Units

°C

Operating temperature

Storage temperature

Power supply voltage

Allowable loss

°C

-0.3~+25

350

(Except where noted otherwise, Ta=25°C, V =15V, Rg=10kΩ, Rs=1000kΩ)

Electrical Characteristics

Item

Symbol

Measurement conditions

Min. Typ. Max. Units

0.45 0.6 mA

See Fig. 1

Consumption current

Gain

I^CC

G^V

GV=K Rs/Rg

Error of above formula

When input range switching pin is high

When input range switching pin is low

Gain error

G^V

-5

Input bias current 1

Input bias current 2

Input offset current

Input offset voltage

O.COM pin setting

voltage range

I^B1

I^B2

I^IO

100

250

-500 nA

V^IO

-2

Output takes O.COM pin

voltage as reference

V^OC

1.0

VCC

-1.5

O.COM pin

input bias current

MM1089

MM1131

100

I^OC

Output offset voltage

Output offset current

Common-mode input range 1

Common-mode input range 2

Input voltage high level

for input range switching pin

Input voltage low level

for input range switching pin

Input current (Hi) for

input range switching pin

Input current (Lo) for

input range switching pin

V^OO

I^OO

VICM1

VICM2

VOC as reference (GV=40dB)

When input range switching pin is high

When input range switching pin is low

0.25

+0.25

µA

0.25

1.8

CC+0.3

0.3

-1.8

V^HSW

V^LSW

I^HSW

2.4

0.8

VINSW=15V

VINSW=0V

-1

µA

I^LSW

-5

-0.5 µA

VIN(+)

VIN(

)=+1V, VO=VCC

1.5V

Output outflow current

I^SOURC

1.0

0.3

4.0

1.0

O.COM=5V

VIN(+)

VIN( )=-1V, VO=0.3V

Output inflow current

I^SINK

O.COM=5V

Slew rate

CMR

0.16

100

V/µS

Common-mode signal rejection ratio

Power supply fluctuation

rejection ratio

SVR

VNI

100

µV

Input equivalent noise voltage

RIN=1kΩ, BPF=20Hz~20kHz

Sensor Amplifier MM1089

MITSUMI

Characteristics

Common-mode input voltage range

Voltage gain vs frequency characteristic

Rg=10kΩ

SV.A

Rg=33kΩ

SV.B

Rg=100kΩ

Rg=1000kΩ

10 12 14 16 18

DC input voltage VICM [V]

10¹

10²

10³

10⁴

10⁵

Frequency f [Hz]

Consumption voltage vs power supply voltage

Maximum output voltage vs Re

0.6

0.5

0.4

Rs=10kΩ

Rs=1000kΩ

Rs=750kΩ

Rs=500kΩ

8 10 12 14 16 18 20 22 24

Power supply voltage VCC [V]

Rs=200kΩ

10²

10³

10⁴

10⁵

Frequency f [Hz]

Power supply fluctuation rejection ratio vs frequency

Common mode component rejection ratio

vs frequency

100

10¹

10²

10³

10⁴

10⁵

10¹

10²

10³

10⁴

10⁵

Frequency f [Hz]

Sensor Amplifier MM1089

MITSUMI

Gain Settings

1. By mounting appropriate external Rs and Rg resistances, a subtractive amp can easily be configured with a

gain Gv=K R^S/Rg (where K=1 typ.).

Here the precision of R^Sand Rg affects the gain, but has no inherent effect on CMR.

However, the practical range for the gain is Gv=3 to 100.

2. To determine R^Sand Rg, first RS is calculated from the maximum required output voltage; then the

equation for the gain Gv=K R^S/Rg is used to compute Rg.

The voltage gain coefficient K varies with the value of Rg. For approximate values of K see Fig.1. The larger

the value of R^S, the larger is the output offset voltage.

If R^Sis made small, an advantageous offset voltage is obtained, but if it is too small, an adequate maximum

output voltage is not obtained.

As a rough estimate, when the maximum output voltage is to be 10V^P

P, Rs=1000kΩ; if it is to be 5VP P,

then Rs=500kΩ.

Recommended values: When Rs=1000 kΩ, Gv=100, Rg=9.1kΩ

When Rs=1000 kΩ, Gv=50, Rg=18kΩ

When Rs=500kΩ, Gv=50, Rg=9.1kΩ

When Rs=500kΩ, Gv=10, Rg=47kΩ

3. The output offset voltage ratings in the table of electrical characteristics are for Rg=10kΩ, Rs=1000kΩ.

When using other constants, use the following formula for the output offset:

Output offset=V^IOGV+IOO RS

4. The output voltage is essentially the voltage applied to the O.COM (OUTPUT COMMON) pin, output as the

reference level. In actuality, an offset is added to the reference potential and output.

Because the O.COM pin is independent of both amps 1 and 2, offset adjustment is easily accomplished by

shifting the O.COM pin voltage by the amount of the offset.

5. If the input range switching pin is set high, the input voltage range is covered from the V^CClevel; by

switching it to low, the range extends from GND level.

However, the offsets are different, so care must be taken in continuous switching.

6. The O.COM pin setting voltage range and common-mode input range should be set to voltages between

the minimum and maximum values.

[Voltage gain coefficient K vs. Rg]

1.00

0.98

0.96

0.94

0.92

0.90

0.88

0.86

0.84

10⁰

10¹

10²

10³

MM1089

Fig. 1 Rg (kΩ)

Sensor Amplifier MM1089

MITSUMI

Application Circuits

1. Charger for NiCad batteries (charging current, discharge current detection circuit)

Note : For the Rg and Rs resistances, see "Gain Settings"

2. Charger for NiCad batteries (charging current, discharge current detection circuit)

Note : For the Rg and Rs resistances, see "Gain Settings"

3. Sensor signal amplification

Note : For the Rg and Rs resistances, see "Gain Settings"

Sensor Amplifier MM1089

MITSUMI

1. Summary

An instrumentation amp is often used as a sensor

amp to amplify weak signals. Among the

advantages of such an amplifier are

1. Good CMR characteristics

2. High input impedance

3. Means of gain adjustment which does not

affect the CMR characteristic

However, in practice an extremely high resistance

precision is demanded, making it difficult to

implement such an amplifier at low cost. In order to

eliminate these problems, Mitsumi developed the

MM1089 sensor amp, with a circuit configuration

providing the above advantages using ordinary

monolithic IC precision.

Fig. 1. Ordinary instrumentation amp

In Fig.1, in a circuit configuration with a gain of

40dB, a resistance precision of 0.1% is necessary

for a CMR of 100dB; for a gain of 20dB, the

precision must be 0.01%. Hence in this IC a circuit

configuration based on an entirely different

operating principle was employed. The approach is

simple: the transistor I^Cvs. VCE characteristic is a

constant-current characteristic not readily

dependent on the voltage. Hence the input signal

voltage is converted into a current signal in the

input unit, and the current component is passed to

the output circuit.

2. Aim of development

The I/O environment in which this IC will be used

was expected to include input sources ranging

from GND to V^CC, while devices receiving the IC

output were anticipated to consist mainly of

microcomputers with integrated D/A converters. In

addition to a high CMR characteristic, the offset

voltage must be kept low; here it was judged that

the output voltage with no input signal could be

easily read in advance and used in the

microcomputer to correct measured values, so that

no measures are taken to force down the offset

voltage unnecessarily. Of course even if a

microcomputer is not used, a potentiometer can be

used to shift the reference voltage applied to the

O.COM pin by the amount of the offset. Emphasis

was placed on a high CMR characteristic and the

ability to accommodate a wide range of input

voltages.

Fig.2. Basic circuit illustrating operation

3. Features of the MM1089

1. CMR characteristic of 100dB and higher

2. Input impedance of 10MΩ and above

3. Broad recommended operating power supply

voltage range (4.5V to 20V using a single power

supply)

4. Broad input voltage range (-0.3V to VCC+0.3V)

5. Range can be set freely (between 10 and 40dB)

using two external resistances

Figure 2 shows the basic circuit.

A simple buffer amp is used to generate a

difference voltage for the input signal across the

resistance Rg, which determines the gain, and the

current I flowing in this resistance is passed

through a current mirror circuit before reaching Rs

of the output amp, to obtain an output voltage

Rs.

6. Reference voltage applied to O.COM pin can

The overall gain is Rs/Rg. The output from the amp

acting as an input buffer depends on two PNP

transistors. The first transistor is connected to one

end of the resistor Rg, a constant-current power

supply, and a feedback loop; the second PNP

transistor has an emitter area only one-half that of

the former transistor, and is connected to a current

mirror circuit and an output circuit.

be set over a broad range (1V to V^CC

-1.5V)

4. Configuration and summary of operation

4-1. Means to achieve high CMR characteristic and

circuit operation

As explained above, the machining precision of

ordinary monolithic ICs (with a resistance precision

of 2%) is such that a high CMR characteristic

cannot be easily obtained in an instrumentation

amplifier.

By this means, an output V^OUTis obtained

consisting of the reference voltage V^COMapplied to

one of the input pins of the output amp, on which

Sensor Amplifier MM1089

MITSUMI

is superposed the input difference voltage Rs/Rg.

The common mode level of the input signal does

not appear in the basic equation, meaning that an

amplifier with an inherently very high CMR

characteristic can be obtained. Of course in the

basic circuit considered here, because of the Early

effect of the transistors the current mirror circuit

operation will not be ideal, and the CMR

characteristic values are as yet insufficient. In the

actual circuit, cascade connections suppress the

Early effect, and a current mirror circuit with an

extremely small voltage dependence was adopted.

Further, a differential amp was not used as the

input buffer amp; instead, a simple configuration

was used to obtain the required characteristics.

Through these circuit designs, a CMR

Fig.3. Pinout

To summarize the block diagram of Fig.3 and pin

functions,

characteristic in excess of 100dB using standard

values was achieved.

1. There are two circuits in a SOP-18P package.

2. Rg and Rs are external resistances. Rg is used

to set the sensitivity, with smaller resistances

yielding higher sensitivity. Rs is used to set the

output scale; to obtain a larger output range,

choose a higher resistance.

(4-2) Means to obtain a broad input voltage range,

and circuit operation

One unavoidable problem is the transistor V^BE

voltage, so that an input circuit which can handle

all voltages from GND to V^CCis inherently

impossible. If a resistance is used to attenuate the

input, a broad range can be achieved; but then the

input impedance cannot be kept high, deviating

from the original development goals.

In actual environments of use there are likely to be

extremely few signal sources with signals varying

continuously from GND to V^CC, and so a design

was adopted in which it is possible to switch

between a mode with an input voltage range of

Rs/Rg is the total gain. In actuality, there is a

degree of error, and so a coefficient K is

included (cf. Fig. 6).

3. The common voltage of the output circuit is

applied to the O.COM pin; when the differential

input is zero, the common voltage is output

without modification (of course the offset

voltage is added).

When there is a differential input, the output

voltage V^Ois

V^O=Vd Rs/Rg K+VC+Vof

0.3V to VCC-1.8 V, and a mode with input

where Vd is the differential input voltage, V^Cis

the common voltage applied to the O.COM pin,

and Vof is the offset voltage. On startup the

offset amount is determined automatically, and

when adding correction V^COMless the offset

voltage is applied.

voltages ranging from 1.8V to V^CC+0.3V. A

switching pin was provided for this purpose.

Specifically, the NPN emitter follower has an input

circuit to shift the voltage in the negative direction,

and the PNP emitter follower has an input circuit to

shift the voltage in the positive direction; these are

switched during use. Because the input offset

voltage is different for the NPN and PNP inputs, in

applications requiring switching during operation

some special measures may be required for offset

correction.

4. Input range switching pins

When the low potential is applied, the input

range from

-0.3V to VCC-1.8V is covered,

when high, the input range is +1.8V to

V^CC+0.3V.

Switching at TTL level is possible. However, it

should be noted that the input offset voltages

are different for the two ranges. Of course if the

IC is to be used fixed at one range, the

switching pin can be shorted to GND or to V^CC.

(4-3) Output circuit and operation

A standard op-amp circuit configuration with a B-

class output stage is adopted. The potential

applied to the+input (O.COM pin) is output as the

reference potential.

5. Major performance parameters

1. Differential gain vs CMR characteristic

Differential gain vs CMR appears in Fig. 4.

When the gain of an ordinary instrumentation

amp is lowered the CMR generally falls, but in

this IC there is almost no change.

Sensor Amplifier MM1089

MITSUMI

2. Input voltage range vs gain

[dB]

130

Shown in Fig. 5. By switching the range using

the input range switching pin, input from GND

level to VCC level is provided.

120

110

100

MM1089

3. Voltage gain coefficient K vs Rg

Rs/Rg nearly coincides with the voltage gain,

with a slight difference. This difference is

represented by K, but as Rg changes K also

changes. This relationship is indicated in Fig. 6.

CMR

Instrumentation amp final stage

0.1%

1.0%

Rs, Rg error

(

)

The output from the MM1089 may be passed

through an A/D converter and input to a

microcomputer for offset correction; an example

appears in Fig.7. Here the inputs IN A and IN B are

signal sources with input voltage ranges extending

to GND level, while IN C and IN D are inputs which

extend to V^CClevel.

1. An analog switch is used to input IN A to both

input pins, the other switches are turned off. A

control output is used to apply the "L" level to

the input range switching pin. Here the output

is V^COM+VOFA, and this is read by the

44[dB]

Differential gain

Fig.4. CMR vs differential gain

[dB]

microcomputer and stored as V^A.

2. Next, an analog switch is used to input INC to

both input pins; other switches are turned off.

Here the input range switching pin is set to "H"

by the control output. The output at this time is

V^COM+VOFB, and this is read by the

L : Input range switching pin low

H : Input range switching pin high

8 10 12 14 16 18 [V]

DC input voltage VICM

microcomputer and stored as V^B. The above

are preparatory measurements.

Fig.5. Common mode input voltage range

3. Analog switches are set so that IN A is at one

input, and IN B at the other; the other switches

are turned off. The control output sets the input

range switching pin to "L" level. Here the

measured value V^X1is the output voltage VO1

less the previously determined VA.

1.00

0.98

0.96

0.94

0.92

0.90

0.88

0.86

G^VK Rs/Rg

V^X1=VO1-VA=(IN A-IN B) GV

10⁰

10¹

10²

10³[kΩ]

4. Analog switches are set to input IN C to one

input pin and IN D to the other; the other

switches are turned off. The input range

switching pin is set "H" by the control output.

The measured value V^X2is the output voltage

V^O2less the previous VB.

Fig.6. Voltage gain coefficient K vs Rg

V^X2=VO2-VB=(IN C-IN D) GV

7. Summary

As explained above, an amplifier which is simple

yet has a high CMR can be configured using the

MM1089.

The MM1089 used together with a CPU equipped

with an internal D/A converter should find a broad

range of applications.

Fig.7. Application example

MM1089 [MITSUMI]

相关型号：

SI9130DB

SI9135LG-T1

SI9135LG-T1-E3

SI9135_11

SI9136_11

SI9130CG-T1-E3

SI9130LG-T1-E3

SI9130_11

SI9137

SI9137DB

SI9137LG

SI9122E