MAX1497 Datasheet, PDF (11/33 Pages) Maxim Integrated Products – 3.5- and 4.5-Digit, Single-Chip ADCs with LED Drivers and μC Interface

3.5- and 4.5-Digit, Single-Chip ADCs with LED
Drivers and µC Interface
Pin Description (continued)
PIN
MAX1497 MAX1499
25
25
26
26
27
27
28
28
—
6
—
7
—
19
—
29
—
30
NAME
FUNCTION
VLED
SEGF
SEGG
SEGDP
AV_DD
DV_DD
DIG4
LED-Display Segment-Driver Supply. Connect to a +2.7V to +5.25V supply. Bypass with
a 0.1µF capacitor to GLED.
Segment F Driver
Segment G Driver
Segment DP Driver
Analog Positive Supply Voltage. Connect AV_DD to a +2.7V to +5.25V power supply.
Bypass AV_DD to GND with a 0.1µF capacitor.
Digital Positive Supply Voltage. Connect DV_DD to a +2.7V to +5.25V power supply.
Bypass DV_DD to GND with a 0.1µF capacitor.
Digit 4 Driver
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.
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.
Detailed Description
The MAX1497/MAX1499 low-power, highly integrated
ADCs with LED drivers convert a ±2V differential input
voltage (one count is equal to 100µV for the MAX1499
and 1mV for the MAX1497) with a sigma-delta ADC and
output the result to an LED or µC. An additional
±200mV input range (one count is equal to 10µV for the
MAX1499 and 100µV 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 µC using an
SPI-/QSPI-/MICROWIRE-compatible serial interface.
Data can either be sent directly to the display or to the
µC 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 (AV_DD + 0.3V) for the MAX1499, and
from VNEG to (V_DD 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.
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