Datasheet

MAX1447/MAX1496/MAX1498
3.5- and 4.5-Digit, Single-Chip ADCs
with LED Drivers
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(PD x T
JA
) max = (+125°C) - (+85°C) = +40°C
PD (max) = +40°C /+105.3°C/W = 380mW
(VLED - V
DIODE
) = [380mW - (5.25V x 2mA) - 5.25V x
1.080mA] / [(127 / 128) x 25.5mA x 8]
VLED - V
DIODE
= 1.854V
VLED - V
DIODE
should have the following condition to
ensure it operates safely:
0.8V < VLED - V
DIODE
< 1.854V
28-Pin PDIP-Package Example
PD x T
JA
(max) = (+125°C) - (+85°C) = +40°C
PD (max) = +40°C / +70°C/W = 571mW
VLED - V
DIODE
= [571mW - (5.25V x 2mA) - 5.25V x
1.080mA] / [(127 / 128) x 25.5mA x 8]
VLED - V
DIODE
= 2.80V
For a 28-pin PDIP package, VLED - V
DIODE
should have
the following condition to ensure it operates safely:
0.8V < VLED - V
DIODE
< 2.80V
32-Pin TQFP Package
The MAX1447/MAX1498 TQFP package can operate
safely for all supply voltages provided V
DIODE
> 1.5V.
Definitions
INL
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. This
straight line is either a best-straight-line fit or a line
drawn between the end points of the transfer function,
once offset and gain errors have been nullified. INL for
the MAX1447/MAX1496/MAX1498 is measured using
the end-point method.
DNL
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of ±1 LSB. A
DNL error specification of less than ±1 LSB guarantees
no missing codes and a monotonic transfer function.
Rollover Error
Rollover error is defined as the absolute-value differ-
ence between a near positive full-scale reading and
near negative full-scale reading. Rollover error is tested
by applying a full-scale positive voltage, swapping
AIN+ and AIN-, and adding the results.
Zero Input Reading
Ideally, with AIN+ connected to AIN-, the MAX1447/
MAX1496/MAX1498 LED displays zero. Zero input
reading is the measured deviation from the ideal zero
and the actual measured point.
Gain Error
Gain error is the amount of deviation between the mea-
sured full-scale transition point and the ideal full-scale
transition point.
Common-Mode Rejection
Common-mode rejection (CMR) 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
only one of the differential inputs. The MAX1447/
MAX1496/MAX1498 sigma-delta converter uses its inter-
nal digital filter to provide normal-mode rejection to both
50Hz and 60Hz power-line frequencies simultaneously.
Power-Supply Rejection Ratio
Power-supply rejection ratio (PSRR) is the ratio of the input
supply change (in volts) to the change in the converter
output (in volts). It is typically measured in decibels.