MAX1499ECJ+【PDF 3/33 页】IC ADC 3 1/2DIG W/LED DVR 32TQFP

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MAX1497/MAX1499

3.5- and 4.5-Digit, Single-Chip ADCs with LED

Drivers and C Interface

______________________________________________________________________________________

Detailed Description

The MAX1497/MAX1499 low-power, highly integrated

ADCs with LED drivers convert a ±2V differential input

voltage (one count is equal to 100V for the MAX1499

and 1mV for the MAX1497) with a sigma-delta ADC and

output the result to an LED or C. An additional

±200mV input range (one count is equal to 10V for the

MAX1499 and 100V for the MAX1497) is available to

measure small signals with increased resolution.

The devices operate from a single 2.7V to 5.25V power

supply and offer 3.5-digit (MAX1497) or 4.5-digit

(MAX1499) conversion results. An internal 2.048V refer-

ence, internal charge pump, and a high-accuracy on-

chip oscillator eliminate external components.

The MAX1497/MAX1499 interface with a C using an

SPI-/QSPI-/MICROWIRE-compatible serial interface.

Data can either be sent directly to the display or to the

C first for processing before being displayed.

The devices also feature on-chip buffers for the differ-

ential input signal and external reference inputs, allow-

ing direct interface with high-impedance signal

sources. In addition, they use continuous internal offset-

calibration and offer >100dB of 50Hz and 60Hz line

noise rejection. Other features include data hold and

peak detection, overrange and underrange detection.

The MAX1499 also provides a low-battery monitor.

Analog Input Protection

Internal protection diodes limit the analog input range

from VNEG to (AVDD + 0.3V) for the MAX1499, and

from VNEG to (VDD to 0.3V) for the MAX1497. If the

analog input exceeds this range, limit the input current

to 10mA.

Internal Analog Input/Reference Buffers

The MAX1497/MAX1499 analog input/reference buffers

allow the use of high-impedance signal sources. The

input buffers’ common-mode input range allows the ana-

log inputs and the reference to range from -2.2V to +2.2V.

Modulator

The MAX1497/MAX1499 perform analog-to-digital con-

versions using a single-bit, 3rd-order, sigma-delta mod-

ulator. The sigma-delta modulator converts the input

signal into a digital pulse train whose average duty

cycle represents the digitized signal information. The

modulator quantizes the input signal at a much higher

sample rate than the bandwidth of the input.

The MAX1497/MAX1499 modulator provides 3rd-order

frequency shaping of the quantization noise resulting

from the single-bit quantizer. The modulator is fully dif-

ferential for maximum signal-to-noise ratio and mini-

mum susceptibility to power-supply noise. A single-bit

data stream is then presented to the digital filter to

remove the frequency-shaped quantization noise.

Pin Description (continued)

PIN

MAX1497

MAX1499

NAME

FUNCTION

VLED

LED-Display Segment-Driver Supply. Connect to a +2.7V to +5.25V supply. Bypass with

a 0.1F capacitor to GLED.

SEGF

Segment F Driver

SEGG

Segment G Driver

SEGDP

Segment DP Driver

—6

AVDD

Analog Positive Supply Voltage. Connect AVDD to a +2.7V to +5.25V power supply.

Bypass AVDD to GND with a 0.1F capacitor.

—7

DVDD

Digital Positive Supply Voltage. Connect DVDD to a +2.7V to +5.25V power supply.

Bypass DVDD to GND with a 0.1F capacitor.

—19DIG4

Digit 4 Driver

—29

LED_EN

Active-High LED Enable. The MAX1499 LED display driver turns off when LED_EN is

driven to logic low. The MAX1499 LED display driver turns on when LED_EN is driven to

logic high.

—30

LOWBATT

Low-Battery Voltage Monitor. When the LOWBATT input voltage is lower than 2.048V, the

LOWBATT bit in the status register is set to one.

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