Datasheet

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General Description

The MAX1491/MAX1493/MAX1495 low-power, 3.5- and

4.5-digit, analog-to-digital converters (ADCs) with inte-

grated liquid crystal display (LCD) drivers operate from a

single 2.7V to 5.25V power supply. They include an inter-

nal reference, a high-accuracy on-chip oscillator, and a

triplexed LCD driver. An internal charge pump generates

the negative supply needed to power the integrated input

buffer for single supply operation. The ADC is config-

urable for either a ±2V or ±200mV input range and it out-

puts its conversion results to an LCD. The MAX1491 is a

3.5-digit (±1999 count) device, and the MAX1493/

MAX1495 are 4.5-digit (±19,999 count) devices.

The MAX1491/MAX1493/MAX1495 do not require exter-

nal-precision integrating or auto-zero capacitors, crystal

oscillators, charge pumps, or other circuitry required

with dual slope ADCs (commonly used in panel meter

circuits). These devices also feature on-chip buffers for

the differential signal and reference inputs, allowing

direct interface with high-impedance signal sources. In

addition, the MAX1491/MAX1493/MAX1495 use continu-

ous internal offset calibration, and offer >100dB rejec-

tion of 50Hz and 60Hz line noise. The MAX1493/

MAX1495 perform enhanced offset calibration at power-

up. The MAX1495 also performs enhanced calibration

on demand. Other features include data hold and peak

hold, and a user programmable low-battery monitor.

The MAX1493/MAX1495 come in a 32-pin 7mm ✕ 7mm

TQFP package, and the MAX1491 comes in 28-pin

SSOP and 28-pin DIP packages. All devices in this fam-

ily operate over the 0°C to +70°C commercial tempera-

ture range.

Applications

Digital Panel Meters

Hand-Held Meters

Digital Voltmeters

Digital Multimeters

Features

♦ High Resolution

MAX1495: 4.5 Digits (±19,999 Count)

MAX1493: 4.5 Digits (±19,999 Count)

MAX1491: 3.5 Digits (±1999 Count)

♦ Sigma-Delta ADC Architecture

No Integrating Capacitors Required

No Autozeroing Capacitors Required

>100dB of Simultaneous 50Hz and 60Hz Rejection

♦ Operate from a Single 2.7V or 5.25V Supply

♦ Selectable Input Range of ±200mV or ±2V

♦ Selectable Voltage Reference: Internal 2.048V or

External

♦ Internal High-Accuracy Oscillator Needs No

External Components

♦ Automatic Offset Calibration

♦ Low Power: Maximum 980µA Operating Current

♦ Small 32-Pin 7mm

✕ 7mm TQFP Package (4.5

Digits), 28-Pin SSOP Package (3.5 Digits), and 28-

Pin DIP Package (3.5 Digits)

♦ Triplexed LCD Driver

♦ Evaluation Kit Available (Order MAX1494EVKIT)

MAX1491/MAX1493/MAX1495

3.5- and 4.5-Digit, Single-Chip

ADCs with LCD Drivers

________________________________________________________________ Maxim Integrated Products 1

TOP VIEW

MAX1493

MAX1495

TQFP

32 28

293031

INTREF

NEG

DPON

GND

BP1

BP2

BP3

1611 12

DPSET2

HOLD

PEAK

SEG2

SEG1

SEG4

SEG3

SEG5

SEG12

24 SEG13

SEG11

SEG10

SEG9

SEG8

SEG7

SEG6

8DPSET1

RANGE

LOWBATT

REF+

REF-

AIN-

AIN+

1AV

PART

TEMP

RANGE

PIN-

PACKAGE

RESOLUTION

(DIGITS)

MAX1491CAI 0°C to +70°C 28 SSOP 3.5

MAX1491CNI 0°C to +70°C 28 DIP 3.5

MAX1493CCJ 0°C to +70°C 32 TQFP 4.5

MAX1495CCJ 0°C to +70°C 32 TQFP 4.5

Pin Configurations

Ordering Information

19-3053; Rev 2; 5/04

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.

Pin Configurations continued at end of data sheet.

EVALUATION KIT

AVAILABLE

Summary of content (25 pages)

PAGE 1
9-3053; Rev 2; 5/04 KIT ATION EVALU E L B A AVAIL 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers Features The MAX1491/MAX1493/MAX1495 low-power, 3.5- and 4.5-digit, analog-to-digital converters (ADCs) with integrated liquid crystal display (LCD) drivers operate from a single 2.7V to 5.25V power supply. They include an internal reference, a high-accuracy on-chip oscillator, and a triplexed LCD driver.
PAGE 2
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers ABSOLUTE MAXIMUM RATINGS AVDD to GND............................................................-0.3V to +6V DVDD to GND ...........................................................-0.3V to +6V AIN+, AIN- to GND...............................VNEG to + (AVDD + 0.3V) REF+, REF- to GND..............................VNEG to + (AVDD + 0.3V) LOWBATT to GND ...................................-0.3V to (AVDD + 0.
PAGE 3
.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers (AVDD = DVDD = +2.7V to +5.25V, GND = 0, VREF+ - VREF- = 2.048V (external reference), CNEG= 0.1µF. All specifications are TMIN to TMAX, unless otherwise noted. Typical values are at +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS LOW-BATTERY VOLTAGE MONITOR (LOWBATT) LOWBATT Trip Threshold 2.
PAGE 4
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers ELECTRICAL CHARACTERISTICS (continued) (AVDD = DVDD = +2.7V to +5.25V, GND = 0, VREF+ - VREF- = 2.048V (external reference), CNEG= 0.1µF. All specifications are TMIN to TMAX, unless otherwise noted. Typical values are at +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.25 V POWER SUPPLY AVDD Voltage AVDD 2.
PAGE 5
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers 0 -0.5 0 -0.5 -10,000 0 10,000 MAX1491/3/5 toc03 10 0 -10,000 0 10,000 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 20,000 NOISE (COUNTS) SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX1493/MAX1495 GAIN ERROR vs. SUPPLY VOLTAGE MAX1493/MAX1495 GAIN ERROR vs. TEMPERATURE 300 DIGITAL SUPPLY 0.04 0.02 0 -0.02 -0.04 -0.06 100 -0.08 0 -0.10 3.25 3.75 4.25 SUPPLY VOLTAGE (V) 4.75 5.25 0 MAX1491/3/5 toc06 0.06 -0.
PAGE 6
Typical Operating Characteristics (continued) (AVDD = DVDD = 5V, GND = 0, REF+ = 2.048V, REF- = GND, RANGE = DVDD, TA = +25°C.) 2.051 2.050 2.049 2.048 2.047 2.046 2.048 2.047 2.046 MAX1491/3/5 toc09 2.049 700 600 SUPPLY CURRENT (µA) REFERENCE VOLTAGE (V) 2.052 2.050 MAX1491/3/5 toc08 2.053 REFERENCE VOLTAGE (V) MAX1491/3/5 toc07 2.054 SUPPLY CURRENT vs. TEMPERATURE INTERNAL REFERENCE VOLTAGE vs. ANALOG SUPPLY VOLTAGE INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE 2.
PAGE 7
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers PIN MAX1493 MAX1495 NAME MAX1491 FUNCTION 1 30 INTREF 2 31 DVDD Digital Power Input. Connect DVDD to a 2.7V to 5.25V power supply. Bypass DVDD to GND with a 0.1µF and a 4.7µF capacitor. 3 32 GND Ground 4 1 AVDD Analog Power Input. Connect AVDD to a 2.7V to 5.25V power supply. Bypass AVDD to GND with a 0.1µF and a 4.7µF capacitor. 5 2 AIN+ Positive Analog Input. Positive side of fully differential analog input.
PAGE 8
3.5- and 4.
PAGE 9
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers The MAX1491/MAX1493/MAX1495 low-power, highly integrated ADCs with LCD drivers convert a ±2V differential input voltage (one count is equal to 100µV for the MAX1493/MAX1495 and 1mV for the MAX1491) with a sigma-delta ADC and output the result to an LCD. An additional ±200mV input range (one count is equal to 10µV for the MAX1493/MAX1495 and 100µV for the MAX1491) is available to measure small signals with increased resolution.
PAGE 10
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers Internal Clock The MAX1491/MAX1493/MAX1495 contain an internal oscillator. Using the internal oscillator saves board space by removing the need for an external clock source. The oscillator is optimized to give 50Hz and 60Hz power supply and common-mode rejection. Y X The MAX1491/MAX1493/MAX1495 contain an internal charge pump to provide the negative supply voltage for the internal analog input/reference buffers.
PAGE 11
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers PEAK MAX1491/MAX1493/MAX1495 HOLD LOW BATT BP1 BP2 BP3 Figure 4. Backplane Connection for the MAX1493/MAX1495 (4.5 Digits) SEG13: PEAK, HOLD, N.C. HOLD LOW BATT PEAK SEG12: F4, E4, DP4 SEG11: A4, G4, D4 SEG2: A1, G1, D1 ANNUNCIATOR SEG1: B1, C1, ANNUNCIATOR SEG3: F1, E1, DP1 SEG10: B4, C4, BC5 SEG4: B2, C2, LOWBATT SEG9: F3, E3, DP3 SEG5: A2, G2, D2 SEG8: A3, G3, D3 SEG6: F2, E2, DP2 SEG7: B3, C3, MINUS Figure 5.
PAGE 12
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers HOLD PEAK LOW BATT BP1 BP2 BP3 Figure 6. Backplane Connection for the MAX1491 (3.5 Digits) SEG10: PEAK, HOLD, BC4 HOLD PEAK LOW BATT SEG2: A1, G1, D1 ANNUNCIATOR SEG1: B1, C1, ANNUNCIATOR SEG3: F1, E1, DP1 SEG4: B2, C2, LOWBATT SEG9: F3, E3, DP3 SEG5: A2, G2, D2 SEG8: A3, G3, D3 SEG6: F2, E2, DP2 SEG7: B3, C3, MINUS Figure 7. Segment Connection for the MAX1491 (3.
PAGE 13
3.5- and 4.
PAGE 14
MAX1491/MAX1493/MAX1495 3.5- and 4.
PAGE 15
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers φ2 φ3 φ1' φ2' MAX1491/MAX1493/MAX1495 φ1 φ3' VLCD ALL OFF 0 VRMS = VLCD / 3 (OFF) -VLCD VLCD a ON g, d OFF 0 VRMS = VLCD / 3 (OFF) -VLCD VLCD a, g ON d OFF 0 VRMS = 1.92VLCD / 3 (ON) -VLCD VLCD ALL ON 0 VRMS = 1.92VLCD / 3 (ON) -VLCD VG = VY - VBP2 (DIFFERENCE BETWEEN SEGMENT LINE Y AND BP2 VOLTAGE) VOLTAGE CONTRAST RATIO = VRMS ON / VRMSOFF = 1.
PAGE 16
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers 100 90 Ø = -10°C 80 Ø = +10°C CONTRAST (%) 70 Ø = -30°C 60 Ø = 0°C 50 40 30 VOFF = 1.1VRMS 20 VON = 2.1VRMS 10 TA = +25°C 0 0 1 2 3 4 5 APPLIED VOLTAGE (VRMS) Ø+ Ø- Figure 12. Contrast vs.
PAGE 17
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers Decimal Point Control The MAX1491/MAX1493/MAX1495 allow for full decimal-point control and feature leading-zero suppression. Use DPON, DPSET1, and DPSET2 to set the value of the decimal point. Tables 2 and 3 show the truth tables of the DPON, DPSET1, and DPSET2 that determine which decimal point is used. Connect INTREF to GND to use the external reference. The external reference inputs, REF+ and REF-, are fully differential.
PAGE 18
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers offers enhanced offset calibration on demand. Connect HOLD to DVDD for 2s to perform enhanced offset calibration. ANALOG SUPPLY FERRITE BEAD Peak The MAX1491/MAX1493/MAX1495 feature peak detection circuitry. When activated (PEAK connected to DVDD), the devices display only the highest voltage measured to the LCD. First, the current ADC result is displayed. Then the new ADC conversion result is compared to this value.
PAGE 19
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers ⎛V ⎞ -V Counts = 1.024 × ⎜ AIN+ AIN- ⎟ × 20,000 ⎝ VREF + - VREF- ⎠ The transfer function for the MAX1493 with AIN+ - AIN< 0 and RANGE = GND is: ⎛V ⎞ -V Counts = 1.024 × ⎜ AIN+ AIN- × 20,000⎟ + 1 ⎝ VREF + - VREF⎠ The transfer function for the MAX1491 with AIN+ - AIN≥ 0 and RANGE = GND is: ⎛V ⎞ -V Counts = 1.024 × ⎜ AIN+ AIN- ⎟ × 2000 ⎝ VREF + - VREF- ⎠ The transfer function for the MAX1491 with AIN+ - AIN< 0 and RANGE = GND is: ⎛V ⎞ -V Counts = 1.
PAGE 20
MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers LCD LCD 1--- 1--- 1999 1999 2 1 2 1 0 0 -0 -0 -1 -1 -2 -2 -1999 -1999 -1--- -1---200mV -100µV 0 100µV +200mV ANALOG INPUT VOLTAGE Figure 17. MAX1491 Transfer Function ±200mV Range -2V -1mV 0 1mV Figure 18. MAX1491 Transfer Function ±2V Range Definitions Supplies, Layout, and Bypassing Power up AVDD and DVDD before applying an analog input and external reference voltage to the device.
PAGE 21
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers Common-Mode Rejection Common-mode rejection is the ability of a device to reject a signal that is common to both input terminals. The common-mode signal can be either an AC or a DC signal or a combination of the two. CMR is often expressed in decibels. Normal-Mode 50Hz and 60Hz Rejection (Simultaneously) Normal mode rejection is a measure of how much output changes when 50Hz and 60Hz signals are injected into just one of the differential inputs.
PAGE 22
3.5- and 4.
PAGE 23
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers 32L/48L,TQFP.EPS ______________________________________________________________________________________ 23 MAX1491/MAX1493/MAX1495 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.
PAGE 24
Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 2 SSOP.EPS MAX1491/MAX1493/MAX1495 3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers 1 INCHES E H MILLIMETERS DIM MIN MAX MIN MAX A 0.068 0.078 1.73 1.99 A1 0.002 0.008 0.05 0.21 B 0.010 0.015 0.25 0.38 C D 0.20 0.09 0.004 0.008 SEE VARIATIONS E 0.205 e 0.212 0.
PAGE 25
3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers PDIPN.EPS 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.