MAX1498ECJ+ Maxim Integrated Products, MAX1498ECJ+ Datasheet - Page 11

• Manufacturer Part Number: MAX1498ECJ+
• Description: IC ADC 4 1/2DIG W/LED DVR 32TQFP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1498ECJ+

• Number Of Bits: 4.5 Digit
• Sampling Rate (per Second): 5
• Number Of Converters: 1
• Power Dissipation (max): 1.65W
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX1447/MAX1496/MAX1498 perform analog-to-
digital conversions using a single-bit, 3rd-order, sigma-
delta modulator. 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 MAX1447/MAX1496/MAX1498 modulator provides
3rd-order frequency shaping of the quantization noise
resulting from the single-bit quantizer. The modulator is
fully differential for maximum signal-to-noise ratio and
minimum susceptibility to power-supply noise. A single-
bit data stream is then presented to the digital filter to
remove the frequency-shaped quantization noise.
The MAX1447/MAX1496/MAX1498 contain an on-chip
digital lowpass filter that processes the data stream
from the modulator using a SINC
Figure 1. MAX1447/MAX1498 Functional Diagram
REF+
AIN+
REF-
AIN-
______________________________________________________________________________________
AV
DD
BUFFERS



+2.5V
INPUT
-2.5V
sin( ) x
DV
x
DD
3.5- and 4.5-Digit, Single-Chip ADCs



4
4
response:
Digital Filtering
REFERENCE
BANDGAP
2.048V
GND
Modulator
TIMING
A = 1.22
ADC
OSCILLATOR
CLOCK
+2.5V
The SINC
periods (4 x 200ms).
The MAX1447/MAX1496/MAX1498 have 25% over-
range capability built into the modulator and digital fil-
ter. The digital filter is optimized for the f
4.9152MHz. The frequency response of the SINC
calculated as follows:
where N is the oversampling ratio, and f
data rate = 5Hz.
CONVERTERS
BINARY-TO-
BCD
CHARGE
PUMP
V
NEG
4
filter has a settling time of four output data
with LED Drivers
-2.5V
H z
H f
( )
( )
I
SET
=
=
DRIVER
MAX1447
MAX1498
N
1




VLED
LED
N
1 1







sin
(
(
1
sin
-



-
N
Z



Z
π
-
f
-
π
m
N
1
f
f
)
m
)
f










4







4
SEG1
SEGF
SEGDP
DIG0
DIG4
LED_EN
GLED
CLK
DPON
DPSET1
DPSET2
RANGE
PEAK
HOLD
m
CLK
= N x output
equal to
4
filter is
11