MAX1497 Maxim, MAX1497 Datasheet - Page 11

• Manufacturer Part Number: MAX1497
• Description: 3.5- and 4.5-Digit / Single-Chip ADCs with LED Drivers and C Interface
• Manufacturer: Maxim

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.
MAX1497
25
26
27
28
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3.5- and 4.5-Digit, Single-Chip ADCs with LED
PIN
MAX1499
25
26
27
28
19
29
30
6
7
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Detailed Description
LOWBATT
LED_EN
SEGDP
NAME
SEGG
SEGF
AV
DV
VLED
DIG4
DD
DD
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
Bypass AV
Digital Positive Supply Voltage. Connect DV
Bypass DV
Digit 4 Driver
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.
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.
DD
DD
to GND with a 0.1µF capacitor.
to GND with a 0.1µF capacitor.
Drivers and µC Interface
Internal protection diodes limit the analog input range
from VNEG to (AV
from VNEG to (V
analog input exceeds this range, limit the input current
to 10mA.
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.
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.
Internal Analog Input/Reference Buffers
FUNCTION
Pin Description (continued)
DD
DD
DD
to a +2.7V to +5.25V power supply.
to a +2.7V to +5.25V power supply.
DD
to 0.3V) for the MAX1497. If the
+ 0.3V) for the MAX1499, and
Analog Input Protection
Modulator
11