MAX5421CEUB [MAXIM]


型号：	MAX5421CEUB
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	DIGITAL POTENTIOMETER\|CMOS\|TSSOP\|10PIN\|PLASTIC 数字电位器\| CMOS \| TSSOP封装\| 10PIN \|塑料\n 电位器
文件：	总9页 (文件大小：323K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

19-2229; Rev 0; 10/01

Digitally Programmable Precision

Voltage Divider for PGAs

General Description

Features

The MAX5420 and MAX5421 are digitally programmable

precision voltage dividers optimized for use in digitally pro-

grammable gain amplifier configurations. The MAX5420/

MAX5421 operate from a single +5V supply or dual 5V

supply, and consume only 3µA supply current. These

devices consist of a digitally selectable resistor array that

provides four precision noninverting gains of 1, 2, 4, and 8

for PGAs. The MAX5420 and MAX5421 achieve a resistor

ratio accuracy of 0.025% (MAX542_A), 0.09% (MAX542_B),

and 0.5% (MAX542_C). The MAX5421 includes an on-chip

matching resistor for op amp bias-current compensation.

ꢀ Four Precision Divider Ratios For Noninverting

Gains of 1, 2, 4, and 8 in PGAs

ꢀ 0.025%, 0.09%, or 0.5% Ratio Accuracy

Guaranteed Over -40°C to +85°C

ꢀ On-Chip Matching Resistor for Op Amp Bias-

Current Compensation (MAX5421)

ꢀ 5V Single or 5V Dual Supply Operation

ꢀ Low 3µA Supply Current

ꢀ CMOS/TTL Logic Compatible 2-Wire Parallel

The MAX5420 and MAX5421 are available in 8-pin and

10-pin µMAX packages. The devices are specified over

the extended temperature range (-40°C to +85°C).

Interface

ꢀ Small 8-Pin and 10-Pin µMAX Packages

Applications

General-Purpose Programmable Noninverting

Amplifiers

Ordering Information

TEMP.

PIN-

GAIN

PART

RANGE

PACKAGE ACCURACY

Programmable Instrumentation Amplifiers

MAX5420AEUA -40 C to +85 C 8 µMAX

MAX5420BEUA -40 C to +85 C 8 µMAX

MAX5420CEUA -40 C to +85 C 8 µMAX

MAX5421AEUB -40 C to +85 C 10 µMAX

MAX5421BEUB -40 C to +85 C 10 µMAX

MAX5421CEUB -40 C to +85 C 10 µMAX

0.025%

0.09%

0.5%

0.025%

0.09%

0.5%

Pin Configurations

Functional Diagram

TOP VIEW

MAX5420

MAX-8

MAX5421

MAX5420

MAX5421

GND

DECODER

MATCH_H

MATCH_L

GND

MAX5421 ONLY

MATCH_H

MATCH_L

MAX-10

________________________________________________________________ Maxim Integrated Products

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Digitally Programmable Precision

Voltage Divider for PGAs

ABSOLUTE MAXIMUM RATINGS

to GND..............................................................-0.3V to +6V

to GND...............................................................+0.3V to -6V

Continuous Power Dissipation (T = +70°C)

8-Pin µMAX (derate 4.1mW/°C above +70°C).............333mW

10-Pin µMAX (derate 5.6mW/°C above +70°C)...........444mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range.............................-60°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

D0, D1 to GND ...........................................-0.3V to (V

+ 0.3V)

H, L, W, MATCH_ to GND................(V - 0.3V) to (V

Input and Output Latchup Immunity................................. 50mA

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

= +5V 5%, V = -5V 5% or V = GND, T = T

to T

, unless otherwise noted. Typical values are at T = +25°C.)

MAX A

MIN

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

0.025

0.09

0.5

UNITS

MAX542_A

MAX542_B

Divider Ratio Accuracy

MAX542_C

(Figure 1)

H-to-L Resistance

Input Resistance at H

= -5V

= 0

300

500

Ratio = 1

Input Resistance at W

Ratio = 2, 4, 8

Capacitance at H, L, W,

MATCH_H, MATCH_L

ANALOG

= -5V

= 0

300

500

Ratio = 1

Ratio = 2, 4, 8

Matching Resistor

MAX5421

DYNAMIC PERFORMANCE

Switching Time

= +5V, V = -5V, digital input 0 to +3V,

settles to 0.02% of final value with 2pF

0.5

µs

capacitive load. Circuit of Figure 2.

DIGITAL INPUTS

Input High Voltage

Input Low Voltage

Input Leakage Current

Input Capacitance

2.4

0.8

D1, D0 = V

or GND

µA

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

ELECTRICAL CHARACTERISTICS (continued)

= +5V 5%, V = -5V 5% or V = GND, T = T

to T

, unless otherwise noted. Typical values are at T = +25°C.)

MAX A

MIN

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

POWER SUPPLIES

Positive Supply Voltage

Negative Supply Voltage

4.75

5.25

-5.25

µA

D1, D0 = V

or GND

Positive Supply Current

Negative Supply Current

D1, D0 = 3V

D1, D0 = V

D1, D0 = 3V

W, H, L, MATCH_L, MATCH_H

Voltage Range

Typical Operating Characteristics

= +5V, V = -5V, or V = GND, T = +25°C, unless otherwise noted.) (Note 1)

MAX542_A DIVIDER RATIO ACCURACY

vs. TEMPERATURE

MAX542_A DIVIDER RATIO ACCURACY

vs. TEMPERATURE

MAX542_A DIVIDER RATIO ACCURACY

vs. TEMPERATURE

0.0010

0.0007

0.0004

0.0050

0.0046

0.0042

0.0038

0.0034

0.0030

0.005

0.004

0.003

0.002

0.001

= +5V

V = +5V

RATIO = 4

V = -5V

RATIO = 1

RATIO = 2

0.0001

-15

-40

-15

-40

-15

TEMPERATURE ( C)

TEMPERATURE (°C)

TEMPERATURE ( C)

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

Typical Operating Characteristics (continued)

= +5V, V = -5V, or V = GND, T = +25°C, unless otherwise noted.) (Note 1)

MAX542_B DIVIDER RATIO ACCURACY

MAX542_A DIVIDER RATIO ACCURACY

vs. TEMPERATURE

-0.0200

0.007

0.006

0.005

0.004

0.003

0.002

0.001

0.0020

0.0015

0.0010

0.0005

= +5V

V = +5V

RATIO = 1

V = -5V

RATIO = 2

RATIO = 8

-0.0225

-0.0250

-0.0275

-0.0300

-40

-15

-40

-15

-40

-15

TEMPERATURE (°C)

TEMPERATURE ( C)

MAX542_B DIVIDER RATIO ACCURACY

vs. TEMPERATURE

MAX542_A RATIO ACCURACY

vs. POSITIVE SUPPLY VOLTAGE

MAX542_B DIVIDER RATIO ACCURACY

vs. TEMPERATURE

0.01

-0.050

-0.055

-0.060

-0.065

-0.070

-0.030

-0.035

-0.040

-0.045

-0.050

= +5V

RATIO = 4

V = -5V

RATIO = 8

RATIO = 4

RATIO = 8

RATIO = 2

0.001

RATIO = 1

= +3V, V = 0

0.0001

-40

-15

4.75

5.00

5.25

-40

-15

TEMPERATURE ( C)

POSITIVE SUPPLY VOLTAGE (V)

TEMPERATURE ( C)

MAX542_B RATIO ACCURACY

vs. POSITIVE SUPPLY VOLTAGE

MAX542_A RATIO ACCURACY

vs. NEGATIVE SUPPLY VOLTAGE

MAX542_B RATIO ACCURACY

vs. NEGATIVE SUPPLY VOLTAGE

0.1

0.01

0.1

RATIO = 8

RATIO = 4

RATIO = 2

0.01

0.001

0.01

0.001

RATIO = 2

RATIO = 4

0.001

RATIO = 8

= 5V, V = 0

RATIO = 1

-1.50

= 5V, V = 0

= +3V, V = 0

RATIO = 1

-2.75

NEGATIVE SUPPLY VOLTAGE (V)

RATIO = 1

0.0001

-4.00

-2.75

-0.25

-5.25

-4.00

-1.50

-0.25

4.75

5.00

POSITIVE SUPPLY VOLTAGE (V)

5.25

-5.25

NEGATIVE SUPPLY VOLTAGE (V)

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

Typical Operating Characteristics (continued)

= +5V, V = -5V, or V = GND, T = +25°C, unless otherwise noted.) (Note 1)

SS SS A

SWITCHING TIME

(RATIO 2-TO-4)

SWITCHING TIME

(RATIO 1-TO-2)

MAX5420/21 toc14

MAX5420/21 toc13

D1, 5V/div

D0, 5V/div

1V/div

2V/div

100ns/div

= +5V, V = -5V

SUPPLY CURRENT

vs. TEMPERATURE

SWITCHING TIME

(RATIO 4-TO-8)

MAX5420/21 toc15

D1, D0 = GND or V

D0, 5V/div

500mV/div

100ns/div

-40

-15

= +5V, V = -5V

TEMPERATURE ( C)

Note 1: For MAX542_C accuracy Typical Operating Characteristics, refer to MAX542_B accuracy Typical Operating Characteristics.

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

Pin Description

NAME

FUNCTION

MAX5420

MAX5421

Positive Supply Voltage

Negative Supply Voltage

Ground

GND

Digital Control Inputs. Drive D0 and D1 logic high or logic low to set the divider ratio.

See Logic Control Truth Table.

4, 5

D0, D1

Low Terminal of Resistor-Divider

Resistor-Divider Output

High Terminal of Resistor-Divider

Matching Resistor Low Terminal

Matching Resistor High Terminal

—

MATCH_L

MATCH_H

Detailed Description

Table 1. Logic Control Truth Table

The MAX5420/MAX5421 are digitally programmable pre-

cision voltage dividers for programmable-gain amplifiers.

Operationally, these devices consist of digitally selectable

precision resistor-dividers providing noninverting gains of

1, 2, 4, and 8 for PGA applications (see Functional

Diagram and Figure 1).

DIGITAL INPUTS

DIVIDER

RATIO

R_B

Ratio

R_A

Digital Interface Operation

The MAX5420/MAX5421 feature a simple two-bit paral-

lel programming interface. D1 and D0 program the

divider ratio setting according to the Logic Control

Truth Table (Table 1). The digital interface is CMOS/TTL

logic compatible.

The MAX5420/MAX5421 achieve divider ratio accuracy of

0.025% (MAX5420A/MAX5421A), 0.09% (MAX5420B/

MAX5421B) or 0.5% (MAX5420C/MAX5421C).

The end-to-end resistance from H to L is 15k . The

impedance seen at W is designed to be the same 8k

for divider ratios 2, 4, and 8, ensuring excellent imped-

ance matching and constant switching times. In gain of

+1 configuration, H is internally connected to W with a

typical resistance of 500 .

Applications Information

Programmable-Gain Amplifier

The MAX5420/MAX5421 are ideally suited for high-pre-

cision PGA applications. The typical application circuit

of Figure 3 uses the MAX5421 with matching resistor to

compensate for voltage offset due to op amp input bias

currents. Use the MAX5420 with an ultra-low input bias

current op amp such as the MAX4237 (Figure 4).

Matching Resistor (MAX5421)

The MAX5421 includes a matching resistor to compen-

sate for offset voltage due to input bias current of the

op amp. The resistance from MATCH_H to MATCH_L,

equals the resistance seen at W for gains of 2, 4, and 8.

In the gain of +1, an internal switch connects

MATCH_H and MATCH_L. This internal switch matches

the impedance of the switch between H and W.

Power Supplies and Bypassing

The MAX5420/MAX5421 operate from dual 5V sup-

plies, or a single +5V supply. For dual supplies, bypass

and V

with 0.1µF ceramic capacitors to GND.

For single supply, connect V

to GND and bypass

with a 0.1µF ceramic capacitor to GND.

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

+5V

RATIO = 1

MATCH_H

MATCH_L

OUT

MAX5421

MAX4493

R2B

R1B

R3B

GND

RATIO = 2

RATIO = 4

RATIO = 8

Figure 3. Programmable-Gain Amplifier with Op Amp Bias-

Current Matching

R3A

R2A

R1A

+5V

R_B

R_A

RATIO =

( )

OUT

MAX4237

+5V

Figure 1. Simplified Functional Diagram

+5V

0.1

MAX5420

GND

RATIO = 1

R2B

R1B

R3B

Figure 4. Programmable-Gain Amplifier

RATIO = 2

RATIO = 4

TEKTRONIX P6245

OSCILLOSCOPE FET

PROBE

RATIO = 8

Switching Time and Layout Concerns

The switching time of the MAX5420/MAX5421 depends

on the capacitive loading at W. For best performance,

reduce parasitic board capacitance by minimizing the

circuit board trace from W to the op amp inverting input,

and choose an op amp with low input capacitance.

< 1pF

R_B

R_A

RATIO =

R1A

(

)

R3A

R2A

MAX5421

D1 D0

Chip Information

TRANSISTOR COUNT: 118

PROCESS: CMOS

0.1

PULSE

GENERATOR

-5V

GND

Figure 2. Switching Time Test Circuit

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

Package Information

_______________________________________________________________________________________

Digitally Programmable Precision

Voltage Divider for PGAs

Package Information (continued)

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9

Printed USA

is a registered trademark of Maxim Integrated Products.

MAX5421CEUB [MAXIM]

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